This article presents the investigation on the epitaxial ZnO films were grown on sapphire substrates only using solution-based processing without any vacuum deposition techniques to preparing epitaxial buffer layers. Prior to hydrothermal growth of ZnO films, poly-crystalline ZnO layers were derived by sol-gel process, and then epitaxial spinel ZnAl₂O₄ buffer layers were formed via solid phase epitaxy. The use of a ceramic ZnO box during solid phase epitaxy can improve the coverage of epitaxial ZnAl₂O₄ grains on sapphire surface, and hence obviously enhance the coalescence of ZnO rods to produce continuous and flat ZnO epitaxial films in the sequential hydrothermal growth. This work is focused on the morphological evolution of epitaxial ZnO films on spinel buffer layers in relation to the preparation conditions of hydrothermal solutions, including the source chemicals, pH value of the solution, and growth duration. In addition, the microstructural characterization of epitaxial spinel ZnAl₂O₄ buffer layer and ZnO films were implemented by SEM, XRD, and TEM techniques, respectively.

This article presents the investigation on the formation of thermally induced pores in epitaxial ZnO films grown on sapphire substrates by using hydrothermal process. The formation of nanometer-size pores in hydrothermally grown ZnO films after annealing treatments can retard the utilization of low-temperature solution route to synthesize ZnO films for optoelectronic device applications. The effect of hydrothermal solutions and annealing conditions on the microstructural and electrical properties of hydrothermally grown ZnO films was systematically studied in this work. After annealing over 400 ^oC, the formation of pores in ZnO films was inevitable, regardless of the films grown from different types of aqueous solutions or annealed in various ambient. However, sizes and densities of the thermally induced pores in ZnO films closely depend on the chemical properties of growth solutions, including pH value and source chemicals. The annealed ZnO films grown from the solution with high pH value (~10.8) contained a larger number of pores and its electrical conductivity and carrier concentration are dramatically reduced after annealing treatment. In contrast, the annealed films grown from the solution with low pH value (<7.5) retained its original electrical properties and a small amount of pores were formed in the films. Furthermore, the detailed microstructure of these thermally induced pores in epitaxial ZnO films was characterized by XTEM observation.

Generalized Fermi-level Shifting (GFLS) model is one of the most highly developed models describing the dopant-enhancement effect in Solid phase epitaxy regrowth (SPER). It has been reported that SPER in doped silicon will have a rate enhancement or retardation due to shifting in Fermi-level. The SPER rate of crystalline Si from amorphous also has a dependence on strain introduced by doping or isovalent impurities by atomic size mismatch. Existing strain included GFLS model assumes additivity of doping and isovalent impurities induced strain for SPER rate enhancement, which is not tested in the tensile strained host lattice regime. In this experiment, C or Ge (isovalent) implanted tensile or compressive strained silicon host substrates had been further implanted with N, P, and As (doping impurities) to result in similar Fermi-level shifting. Due to the atomic size difference of N, P and As, the C and Ge introduced strain in silicon may be increased or reduced. We found by in situ-time resolved reflectivity measurement, that the strain reduced SPER rate competes with dopant induced Fermi-level shift. Large atomic size dopant relaxes the strain in the host lattice and result in enhanced SPER rate. Nonetheless, while the compressive strain induced by Ge does retard SPER as predicted, the tensile strain induced by C does not enhance SPER rate as predicted by existing model. The above finding suggests the non-additivity of doping and isovalent impurities induced strain in SPER rate enhancement. We therefore propose a modified version for the better description of the strain included GFLS model.

A novel blue-emitting phosphor of titanium-doped zinc spinel (ZnAl₂O₄:Ti) nanopowder was prepared by a simple sol–gel method. The effects of dopant concentration and heat treatment on the crystallization process and luminescent property of the powder phosphor were investigated. The doping of Ti did not noticeably affect the crystallinity of the phosphor, while the crystallite size and lattice constant slightly increased as the doping level increased. X-ray diffraction (XRD) revealed that the xerogel powders were amorphous up to 250^oC annealing and crystallized into a single-phase ZnAl₂O₄ structure after annealing at 300^oC and above. The mean crystallite sizes of the powder phosphor were varied from ~10 to 25 nm for samples annealed in the range of 300–1000^oC. Field-emission scanning electron-microscopy (FE-SEM) observation exhibited the 1000^oC-heated powders had primary particle sizes of around 25~30 nm and narrow size-distribution. Photoluminescence (PL) results showed that the phosphor revealed a broad blue emission band peaking at around 435 nm under excitation of 280 nm ultraviolet (UV) light, which were ascribed to the charge-transfer transitions of Ti⁴⁺ + O^2–→ Ti³⁺ + O⁻. Controlling the dopant concentration and heating temperature could significantly enhance the luminescent intensity. The results showed that this phosphor could serve as a potential candidate for application as a blue component phosphor for UV-converting white light-emitting diodes.

we have fabricated different kinds of Si bicrystals by controlled wafer bonding. One-dimensional dislocation arrays were formed in bicrystals by bonding of (111) or (110) Si wafers with (001) SOI wafers while two-dimensional dislocation networks were formed by wafer bonding of (001)Si and (001)SOI wafers. The dislocation network was composed of pure screw dislocations between single crystals Si substrate and a transferred monocrystalline Si layer. NiSi₂ formed on the bicrystal was found to be affected by the underlying dislocation arrays, confined by the dislocation grids. It has been demonstrated that through controlling the surface stress arrangement, the shape of the silicide nanostructures can be controlled and various nanostructures can be obtained. This study supports the fundamental understanding of the stress effect on the formation of the silicide nanostructures on Si bicrystals and the shape controlled nanosilicide could be useful on the growth of the catalyst-assisted one-dimensional nanostructures.

Zinc oxide (ZnO) and Ni-doped zinc oxide with Ni seed layer (Ni/ZnO:Ni) nanocolumns are prepared by radio frequency (RF) magnetron sputtering technique  at room temperature on Si (111) and glass substrates. ZnO was grown by sputtering 99.999 % ZnO target with 200 W RF power for 1 hour while Ni/ZnO:Ni was grown by sputtering 99.999 % Ni target only with 50W RF power for 5 minutes continued by co-sputtering of Ni and ZnO target with RF power 50 W and 200 W respectively for 1 hour. The grown films were deposited using a mixture of argon and oxygen gases.  The objective of this work is to  grow transparent conductive oxide (TCO) material and understanding its physical properties. The X-ray diffraction (XRD) results show that crystalline phases occurred at (002) and (103) planes of the nanocolumns for both samples. Optical transmittance spectra reveal that the samples have excellent optical properties. The average transmittance for  undoped ZnO  nanocolumns was determined to be ~100% in the visible light region, which is more than that ~97% of Ni/ZnO:Ni nanocolumns. Optical studies of the nanostructured zinc oxides showed a decrease in band gap with increasing concentration of Ni dopant and Ni seed layer . Field emission scanning electron microscopy (FESEM) surface analysis shows that uniformity of the nanostructure Ni/ZnO:Ni sample  is improved by Ni incorporation.  The atomic force microscopy (AFM) also shows the Ni/ZnO:Ni smooth surface layer compared to only ZnO.

In this study, polycrystalline silicon (Poly-Si) thin films were fabricated on glass substrate by aluminum induced crystallization (AIC) process. 150 nm thick aluminum film was deposited on a glass substrate using DC magnetron sputtering. A 350 nm thick amorphous silicon (a-Si) layer was then deposited onto Al film by RF magnetron sputtering. To perform the AIC of the layered structures, the samples were annealed in Ar ambient at temperatures ranging from 450oC to 550oC for between 1 and 24 hrs. The resulting poly-Si films were investigated using X-ray diffraction, optical microscope (OM) and scanning electron microscopy (SEM). From results of XRD and metallographic analysis, it was demonstrated that the crystalline structure of the poly-Si films prepared by AIC. The influence of annealing temperature and time on the crystallization of a-Si film were discussed.

Recent years, there are plenty of reports showing quasi-one-dimensional nanostructures of metal oxides exhibit better gas sensing properties compared to their thin films. Although their sensing properties are improved, there are still rooms for further improvement. In this paper, we suggested an approach to further enhance the sensing properties of metal oxide nanowires (NWs)  by using the p-n junction (diode) structured sensors. This paper describes the fabrication of diodes for both ZnO and CuO NWs on silicon substrate. The diodes have been formed by electrochemical growth of ZnO and CuO NWs on p-type boron doped silicon and n-type phosphorus doped silicon respectively. Gas sensing properties of both ZnO and CuO sensors have been examined by measuring the resistance change of both samples towards reduction and oxidation gases. Significant improvement of sensing behaviour reduced optimum operating temperature was observed from both diode-based samples. The sensing mechanism of the diode-based gas sensors will be further discussed. These sensing properties make them promising sensitive and reliable chemical sensors which are useful in future sensing devices.

III-nitrides have been intensely studied in recent years because of their huge potential for various applications such as optoelectronics, high-power high-frequency and high-temperature electronics. III-Nitrides (AlN, GaN and InN) are direct bandgap semiconductors with unique optical and electrical properties [1]. One dimensional nanostructure such as nanowires (NWs) and nanorods (NRs) are expected to be the functional building blocks for future nanoelectronics, optoelectronics, sensors and photovoltaic applications [2]. Here, we report the fabrication of self-assembled GaN and InGaN nanostructures using chemical vapor deposition under vapor-liquid-solid (VLS) and vapor-solid (VS) approach. A customized CVD reactor is assembled with the state of art of accessories such as mass flow controller, pressure regulator, throttle valve, capacitance manometer and temperature controller sourced externally suitable for nitride activities. By controlling the growth parameters such as the reactor pressure, cell temperature of the source (metal Ga) and the substrate temperature we were able to produce different GaN nanostructures which includes quasi-aligned vertical standing NWs, entangled NWs, high electron transparent nanosheets, micro/nanotowers, butterfly like structure and hexagonal microcrystals [3-5]. The growth mechanism of GaN nanostructures with manifold morphologies was interpreted with surface diffusion model by accounting the direct impingement and surface migration of adatoms. The structural and the optical properties of such manifold morphologies will be discussed in detail.

References:

1. R. Yan, D. Gargas, P. Yang, Nature Photonics, 2009, 3, 569.

2. X. Duan, Y. Huang, Y. Cui, J. Wang, C.M Lieber, Nature London, 2001, 409, 66.

3. V. Purushothaman, V.  Ramakrishnan, K. Jeganathan, CrystEnggComm, 2012, 14, 8390–8395.

4. V. Purushothaman, V.  Ramakrishnan, K. Jeganathan, RSC Advances, 2012, 2, 4802-4806.

5. V. Purushothaman and K. Jeganathan, J. Phys. Chem. C – under review.

Nickel oxide (NiO) films have attracted a lot of attention, due to its good optic, electronic, magnetic properties and chemical stability. It can be fabricated by different physical and chemical vapour deposition techniques, including sputtering, plasma-enhanced chemical vapour deposition, and pulsed laser deposition Recently, some researchers have reported that the as-deposited films can do further special treatment of the surface to enhance the stability of the films and to reduce the surface impurity. Using ion bombardment on the specimen is a promising way of modifying the surface properties, which is often effective in the enhancement of material properties [1].

In this study, the NiO-Ag composite films having Ag content of 6.17 at.% are deposited on corning 1737F glass substrate at ambient temperature by radio frequency (rf) sputtering of NiO-Ag composite target, with oxygen ion source assistance from direct current (dc) ion gun at a power of 150 W. Then post-treatments were performed by Ar ion beam (from ion gun at a power of 100 W) bombardment on the as-deposited NiO-Ag films in order to investigate the effect of Ar ion bombardment time on the structures and optoelectronic properties of the films. The electric resistivity is 1.5×10^-2 Ω-cm when the NiO-Ag composite film is obtained without Ar ion beam bombardment. For the first 20 min of ion beam bombardment, there is no markedly change in electric resistivity. However, it drops significantly to 7×10^-3 and 3×10^-3 Ω-cm when the bombardment time reaches 30 min and 40 min, respectively. On the other hand, the X-ray diffraction patterns show that the NiO-Ag composite films that are obtained without Ar ion beam bombardment only display weak NiO peaks. The crystallinity of NiO degrades greatly when the NiO-Ag composite films are post bombarded with Ar ions. Furthermore, upon further increasing the Ar bombardment time to above 30 min, a (100) peak of Ni₂O₃ appears.

Reference

 [1] R. Hong, J. Huang, H. He, Z. Fan, J. Shao, Appl. Surf. Sci. 242 (2005) 346.

In this study, the non-stoichiometric NiO films are deposited on corning 1737F glass substrate at ambient temperature by radio frequency (rf) sputtering of NiO target with oxygen ion source by ion gun varying direct current (dc) power from 0 W to 150 W at 40 sccm oxygen flow. An ultra high electric resistivity is achieved that cannot be detected by four-point probe measurement when the NiO film is deposited without oxygen ion beam assistance. However, it drops significantly to 0.49 Ω-cm as oxygen ion source powered by a supply of 80 W is introduced. The electric resistivity of NiO films decreases continuously from 0.18 to 0.13 Ω-cm when the power is further increased from 100 to 150 W. The Hall measurements for all NiO films deposited with oxygen ion source assistance show p-type conduction. It is found that the crystallinity of the NiO films becomes worse when oxygen ion beam is added during deposition of the films. On the other hand, the transmittance of NiO film deposited without ion source assistance is around 69 %. It decreases significantly to 35 % when the dc power of oxygen ion gun is increased to 80 W. Upon further increasing the power to 100 W, 120 W, and 150 W, the transmittance of the films decreases further to 33 %, 28 % and 22 %, respectively.

AlN is a material used for development of many new electronic devices including LED and photodetectors in DUV range, AlN-on-silicon platform for low loss, wide-band optical guiding, and MEMS resonators. With desirable critical dimensions (CD) of devices moving into submicron range, wet etching of AlN became obsolete and development of robust dry etching of AlN is of high importance. Though some studies on AN plasma etching were performed in the past, there is a lack of data on etch process development in modern fab equipment for 200 mm wafers.  

In our work AlN with orientation (002) was deposited by RF sputtering with biased wafer chuck. Etching study was performed by design of experiments in a commercial inductively coupled plasma source using the following process variables: gas flow ratios in the gas mixture of Cl2/BCl3/Ar and bias power. All output process parameters important for submicron technology were studied. These included etch rate, roughness, selectivity to SiO2 hard mask and bottom Mo, etch CD bias, sidewall slope, micro-trenching, loading and RIE lag effects. Using Cornerstone software, data were subjected to regression analysis and models were generated representing correlation of input variables and etching results. As a result we were able to establish smooth etching recipes for  sloped 2um- contact vias to bottom Mo  and  trench structures for resonator applications in 1µm –thick AlN with minimal dimensions of 0.5 µm and sidewall angle of 85°.

Sputtering has been widely employed in obtaining high quality ITO films. Sophisticated processing conditions and inefficient use of raw materials however are intrinsic processing limitations for sputtering. Solution-based processing offers simple/effective method for forming ITO films.In this study, ITO films were formed on soda-lime-silica glass substrates by employing modified sol-gel routes. The coating sols were prepared using indium (InCl₃∙4H₂O) and tin-salts (SnCl₄∙5H₂O). The stable coating sols were obtained using ethanol (C₂H₅OH) and acetylacetone (C₅H₈O₂) as solvents by the addition of oxalic acid dihydrate (C₂H₂O₄∙2H2O or OAD) in different amounts.  The effect of oxalic acid content in the sol formulation and post-coating calcination treatment in air (at 300-600 °C) on electrical/optical properties of ITO films have been reported. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with oxalic addition. Oxalic acid modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45±3  nm). ITO films exhibiting high transparency (≈98%, visible region) with a sheet resistance as low as 3.8±0.4 kΩ/sqr have been formed by employing coating sols with optimized oxalic acid amount. The mechanisms and factors affecting the functional performance of oxalic acid -modified films have been thoroughly discussed and related with regulations in the microstructural and chemical characteristic of the films upon oxalic acid addition.

Magnetoresistance (MR) of non-magnetic p-n junction is an important issue in modern semiconductor electronic devices. Here we report a pronounced MR effect in a vertical p-n junction based on silicon. A 1500% MR at room temperature can be reached in the p-n junction for a bias 6 V and applied magnetic field 2 T. The amplitude of MR and field sensitivity of the effect are obviously improved with the decreasing temperature. The large MR effect not only origins from the inhomogeneous scattering in space charge region but also from the change of the space charge region due to Lorenz effect. The new mechanism indicates that the low magnetic field sensitivity in non-magnetic materials can be efficiently improved by designing the proper space-change configuration in p-n junction.

This study investigates the formation energies, electronic structures and optical properties of Ga-doped ZnO with various concentrations of Ga using density functional theory and the Hubbard U (DFT + Ud + Up). The difference in lattice constants between calculated results and experimental measurements is within 1%, and the calculated band gap of pure ZnO is in excellent agreement with experimental values. Results show that donor concentration increases with an increase in Ga concentration; however, electrical conductivity is reduced when localized states close to the Fermi level occur with high levels of Ga doping. Following the incorporation of Ga into ZnO (1.4-6.3 at%), the average transmittance of light in both the visible and UV ranges exceeds that of ZnO. However, the stronger and wider donor states obtained from high doping levels (12.5-25 at%) significantly decreases the average transmittance. Thus, selecting a suitable doping level is crucial to optimizing the photoelectric performance of Ga-doped ZnO. This study also provides a theoretical explanation for the factors influencing these properties.

Zinc oxide (ZnO, wurtzite structure) crystal growth and device technology continues its progress both in terms of materials synthesis as well as device performances. Alloying with MgO yields the band gap shift into the ultraviolet (UV) range of the spectrum of light depending on the composition of MgZnO that may be exploited as barrier films in MgZnO/ZnO superlattices and quantum wells. Therefore, UV lasing, fabrication of UV diode laser, and light-emitting diode (LED) structures emitting in the blue spectral range could be demonstrated. To our knowledge, the growth of single crystalline MgZnO films from low-temperature aqueous solution has not been reported yet. In our work, homoepitaxial growth of single crystalline zinc oxide, ZnO, and magnesium zinc oxide, Mg_xZn_1-xO, films has been carried on under mild conditions (90^oC and ambient pressure). Magnesium incorporation of x = 0.92 mol% was obtained while maintaining single phase wurtzite structure. From the high-resolution X-ray diffraction, secondary electron microscopy, and photoluminescence results, the structural and optical properties of the films strongly depends on the polar growth surface .The use of trisodium citrate, Na₃C₆H₅O₇, yielded more coalesced and mirror-like homoepitaxial films whereas adding magnesium nitrate hexahydrate, Mg(NO₃)₂. 6H₂O, favors the growth of films with pronounced faceting. The effect of solution on the Mg_xZn_1-xO film growth will also be discussed, comparative to the hydrothermal growth under supercritical conditions around T = 350 °C and p = 108 Pa and epitaxial growth of Mg_xZn_1-xO films under water-free conditions.

Solar energy is commonly considered to be the ultimate solution to our need for clean, abundant, and renewable energy resources in the future. The wide-band-gap semiconductor zinc oxide (ZnO) has attracted much attention as a fascinating alternative to TiO₂ photo-anode in DSSCs. This is because ZnO and TiO₂ exhibit similar lowest conduction band edges and electron injection process from the excited dyes. Additionally, the lifetime of carriers in ZnO is significantly longer than that in TiO₂ and in comparison to TiO₂, ZnO has a higher electronic mobility, which is favorable for electron transport. The ZnO-TiO₂ core shell design was found to improve the cell efficiency. This chemically stable shell will protect the ZnO nanorod’s surface from dissolving in the dye, leading to the formation of Zn²⁺/dye complex layer on surface.

In our work, high aspect ratio ZnO nanorod arrays were synthesized on fluorine-doped tin oxide (FTO) glasses via low temperature solution method. By adjusting the growth condition and adding Polyethylenimine (PEI), the ZnO nanorod arrays with tunable length were successfully achieved. The ZnO-TiO₂ core shells structures were realized by fast growth method of ZnO nanorod arrays emerging in the (NH4)₂•TiF₆ solution. TEM, XRD and PL measurement confirmed the existing of titana shell, uniformly covers the ZnO nanorod’s surface. ZnO-TiO₂ core shell nanorod dye-sensitized photovoltaic cells have been fabricated and compared with cells built from ZnO nanorods without shells. Results showed that TiO₂ shell helped to suppress recombination and demonstrated significant enhancement in short circuit current (from 4.2 to 5.2 mA/cm²) , open circuit voltage (from 0.6v to 0.8V) and fill factor (from 42.8% to 73.02%) , leading to as much as triple improve overall conversion efficiency (from 1.1% to 3.03%). Coating the ZnO nanorod arrays with titian shell 10-20nm in thickness caused a dramatic increase in VOC and fill factor, possibly by increasing the efficiency of exciton dissociation across the dye-metal oxide interface and acting as an energy barrier to retard recombination.

Macroporous TiO₂/ polyacrylonitrile (PAN) and TiO₂/carbon hybrid films are fabricated directly by spin coating. Macroporosity is promoted under the conditions favoring the growth of instabilities and dewetting of the spin coated films such as lower film thicknesses, higher evaporation rates and lower molecular weights (viscosity). The synthesis of the hybrid film is achieved by a two-step process. First, TiO₂ powder mixed with PAN in N, N-dimethyl formamide (DMF) solvent is cast as a thin film on a silicon wafer by spin coating. Second, heat treatment at 900^oC produces pure rutile TiO₂ nanocrystals and concurrently pyrolyzes PAN to a porous glassy carbon matrix. The resultant TiO₂/carbon hybrid porous films exhibit excellent photocatalytic activity as shown for the degradation of Rhodamine B dye in aqueous medium.

Compositionally graded Ba-doped NFO multi-layer thin films with a thickness of 50 nm were epitaxially grown on SrRuO₃-buffered SrTiO₃, and transparent MgO substrates by pulsed laser deposition (PLD) method. The composition was varied from pure NFO (bottom), 2%Ba-doped, 4% Ba-doped, 6% Ba-doped, 8% Ba-doped, to 10% Ba-doped NFO (top).  A cubic-on-cubic growth manner was observed for both films. The optical bandgap was determined to be 3.37 eV. Electrical impedance and leakage current were studied at different temperatures from room temperature to 150^oC.  The contributions from bulk grains and interfaces (grain boundaries and inter-layer interfaces) were resolved and analyzed based on the Cole-Cole plots, both of which decreased rapidly with temperature. It was found that the resistance from the interfaces dominated the electrical behavior of the films.

Anode-supported micro-tubular solid oxide fuel cells (SOFCs) are manufactured by aqueous electrophoretic deposition (EPD). The process of these micro-tubular SOFCs includes sequential aqueous EPDs of a porous anode layer (8YSZ-NiO), a dense electrolyte layer (8YSZ), and a porous cathode layer (LSM) onto a thin wire electrode, followed by stripping, drying, and a single-step co-sintering. The microstructure of the micro-tubular SOFCs, including the thickness and porosity of each layer, is controlled by the processing parameters such as solid loading, current density, deposition time, and sintering temperature. In particular, the effects of the thicknesses of the electrolyte and anode layer on the electrochemical performance of such micro-tubular SOFCs are investigated and discussed based on the microstructural and voltage–current–power analyses.

Hydrophobic coatings have recently gained significant attention due to their potential applications in anti-icing and self-cleaning products. However, most hydrophobic or superhydrophobic surfaces do not possess good mechanical properties. Extensive work is being done to enhance their mechanical strength, toughness, durability and resistance to abrasion. In this study, we present a novel hybrid coating which has both good mechanical strength and hydrophobic functionality. Various characterization techniques like contact angle (CA) measurement, nanoindentation, and tape-adhesion test were used to determine the properties of the coatings. Two types of hydrophobic agents, fluorinated alkoxy silanes (FAS) and polydimethoxysilane (PDMS) were used in combination with a hybrid organic-inorganic precursor matrix. It was observed that fluorinated nano-silica fillers (15 wt%) produce superhydrophic CA of 164° and sliding angle < 2°. As for the polymeric additive PDMS, though it produced CA of only hydrophobic CA of 120°-125°, it has sliding angles around 5°-10° which could be of particular use for self-cleaning applications.

High power and low power DC magnetron sputtered Al film was studied at different substrate temperature. The film stress of 7000A Al film was measured use FSM 128 system. It was shown that both low power and high power Al film have comparable tensile stress and it increased with the increased substrate temperature. Film surface roughness was characterized use atomic force microscopy. It was noticed that Al film surface is smooth at low temperature for low power and high power sputtered film and becomes rough when substrate temperature increased. The reflectivity data of Al film also corresponding with their surface roughness. It was also observed that the grain size of low power sputtered film changed more obvious than the high power sputtered film. Al film grain size changing was also supported by film resistivity data. The film resistivity decreased with film grain size increased as less grain boundary scattering contribution when film grain size becomes big.

An extended- gate field- effect transistor (EGFET) with TiO₂ films as the pH sensor was investigated and demonstrated in this work. The sensing material, TiO₂ film, was synthesized by the simple and facile thermal oxidation method. At first, a titanium substrate was cleaned and washed with acid solution. Subsequently, it was calcined in air to form a TiO₂ film. The calcination was performed in the temperature range of 300 – 800 ^oC. For the pH measurements, the TiO₂/Ti sample was further packaged as the pH sensing gate connected to the commercial MOSFET device. The resulting TiO₂ film was characterized with SEM, XRD, EDX, etc. Moreover, influences of acid-washing and calcination temperature on the pH sensing characteristics were under investigation. 

From the experimental results, it showed that the TiO₂-based EGFET device exhibited a quite good sensitivity toward hydrogen ions with high linearity, reliability, and response rate in the pH range from 2.0 to 12.0. Furthermore, the sensing hysteresis during pH measurements was not obvious, and the drift phenomenon was not considerable. The device which TiO₂ gate was obtained at calcination temperature of 500 ^oC showed the maximum pH sensitivity of 56.20 mV/pH with a linearity of 0.9934. Besides, the gate undergone acid-washing treatment showed higher pH sensitivity than that without acid-washing, due to providing more binding sites. In the sensing temperatures of 10-50 ^oC, the pH sensitivity of the device was increased with increasing the temperature approximately obeying the Nernst relationship. In conclusion, the TiO₂-based EGFET device showing excellent pH sensing performances proved it as a very promising pH sensor in the future practical development.

In present work, we have investigated that cerium (Ce) doped SnO₂ nanowires with average diameter of 90 nm can be grown at atmospheric pressure. The Ce-doped SnO₂ nanowires have been synthesized by thermal evaporation of source precursors onto silicon substrates into a horizontal tubular furnace. The nanowires were grown with different concentration of Ce dopant while all other growth parameters such as process temperature, flow rate of carrier gas and distance between source precursors to substrate were kept constant. The scanning-and transmission-electron-microscopic analysis shows that the diameter of Ce-doped SnO₂ nanowires is about 90 nm and their length is about 50 μm. The EDX spectra confirm the doping of Ce into SnO₂ nanowires and the amount of Ce into SnO₂ nanowires is varying from 0.05 at% to 0.1 at%. The synthesized Ce-doped SnO₂ nanowires show tetragonal rutile structure of SnO₂ and X-raydiffraction also showed that Ce gets incorporated into the SnO₂ lattice. The corresponding HRTEM and SAED pattern of Ce-doped nanowires confirm their crystalline nature and crystal structure. As synthesized Ce-doped SnO₂ nanowire based sensor showed a high response to ethanol. These results were thought to be correlated with Ce distribution on the SnO₂ surface and its effective contribution towards the conductivity and crystallite size of the Ce doped SnO₂ nanowires.     

Nickel oxide is a good candidate for temperature sensing applications because of the large temperature coefficient of resistance (TCR). Due to the low electrical conductivity of pure nickel oxide, various dopants have been added into nickel oxide to improve its conductivity. In this research, carbon blacks were combined with nickel oxide to help the conductivity of the printed thin films. Nickel oxide/carbon black (NiO/CB) composite materials for thermistor were prepared by chemically depositing nickel hydroxide onto carbon black nanoparticles and thermally annealed at 300 °C. NiO/CB composites of various Ni to C ratios were prepared by mixing precursors with different atomic Ni/C ratios in the synthetic route. The crystalline structures of NiO/CB composites were analyzed by XRD. The grain size and surface morphology of prepared composite powders were also examined with SEM, and the actual C/Ni ratios in the sintered powders were evaluated by EDX. NiO/CB paste was prepared by suspending NiO/CB composites in ethylene glycol to fabricate sensing elements on glass slides. The resistance of the sensing element was measure by two-point method in the range of 50 to 200oC with a sensitivity coefficient of -4.00%/K.

A hybrid CMOS inverter employing In-Ga-Zn oxide (IGZO) (inorganic, n-channel) and P3HT (organic, p-channel) thin film transistors (TFTs) is reported. Both inorganic and organic TFTs are fabricated by ink-jet printing technology. The field effect mobility of p and n channel TFTs are 0.0038 and 0.27 cm²/V s, respectively. The inverter exhibited an obvious inverter response for switching between logic ‘1’ and logic ‘0’, and yielded a high gain of 14 at V_DD = 30 V. With the combining advantages of oxide semiconductor (n-type, high mobility) and organic (commonly p-type), it is promising to construct powerful functional CMOS circuits, such as ring oscillator and shift registers.

Transparent conductive oxides such as doped zinc oxide and indium tin oxide are extensively used as transparent electrodes in a variety of applications due to their high electrical conductivity and optical transparency in the visible spectrum. However, all these materials are of n type in nature and their use as oxide semiconductors is somewhat limited due to their monopolarity. The use of TCOs to a wider range of active device applications such as UV light emitting diodes, UV detectors, solar cells, etc., calls for the development of p-type TCOs.

Transparent conducting amorphous p type CuBO₂ thin films were grown by rf magnetron co- sputtering at room temperature, using copper and boron targets in oxygen atmosphere. The structural, electrical as well as optical properties were studied . Composition of the films were analysed by XPS measurement. Amorphous structure of as deposited films were confirmed by HRXRD. Surface morphology of the films were analysed by AFM studies. P-type nature and concentration of carriers were studied by Hall effect measurement. The transmittance of the films in the visible region was about 80–90%  which was found to be increased with  atomic percentage of boron. Band gap of the films were found to increase with the atomic percentage of boron. As deposited amorphous CuBO₂ thin films with lower carrier concentration can be used as a channel layer for thin film transistors.

Nanoporous materials of Ca_(10-x)Fe_x(PO₄)₆(OH)₂ (FeHAp, x = 0, 0.1, 0.2, and 0.3) were successfully synthesized by sol–gel method. To obtain nanoporous FeHAp, the prepared precursors were calcined in air at 600 ^oC for 2 h. The samples were characterized by X–ray diffraction (XRD) and transmission electron microscope (TEM) observation. The XRD results confirm the formation of of HAp phase with a small trace of b- TCP phase. The crystallite sizes of the powder were found to be 30–60 nm as evaluated by the XRD line broadening method. The morphology of the samples was nanoporous particles of size less than 100 nm as evaluated by TEM. With increasing the Fe-substituted, the particle size of the FeHAp decreased. The corresponding selected area electron diffraction (SAED) analysis further confirms the formation of hexagonal structure of HAp.

Platinum-loaded titania nanotubes (Pt-TNTs) were fabricated on the quartz substrate as the resistive-type hydrogen sensor. At first, TNTs were formed on the quartz substrate by anodization and followed by calcining at 500^oC in O₂. Subsequently, Pt nanoparticles (Pt NPs, around 3 nm) were deposited on the surface of TNTs. Effects of sputtering time on the electric property and hydrogen sensing characteristics of devices were investigated.

The experimental results indicated that current-voltage characteristics of all studied devices obeyed the Ohm’s law. The electric resistance of the device increased with the increase of sputtering time, whereas it decreased contrarily as the sputtering time larger than 40 seconds. As exposed to hydrogen, hydrogen molecules adsorbed on the TiO₂ surface accompanying with the release of electrons to TiO₂; it would cause the increase of the response current. The TNTs device (Pt0) showed a sensitivity of 1.8×10⁵ toward 1.02%H₂/Air at 303 K. Among various devices with different Pt sputtering time, it was found that the Pt40 device (sputtering Pt for 40 s) exhibited the largest background resistance in air. Moreover, this device demonstrated the highest sensitivity toward hydrogen over the hydrogen concentration range of 11 ppm-1.02 %. At 303 K and 1.02 % H₂/Air, the sensitivity of the Pt40 device reached to 4.6×10⁶, and the response time and recovery time were 952 s and 8 s, respectively. As compared with Pt0 device, the sensing characteristics of the Pt40 device exhibited a great enhancement both in the sensitivity and response rate due to the presence of Pt NPs. Furthermore, high selectivity toward hydrogen was achieved with respect to NH₃ and NO₂, respectively.

VOx films were deposited by radio-frequency reactive magnetron sputtering from a vanadium target in pure O₂ atmosphere. The films were respectively annealed at 200 ℃, 300 ℃, 400 ℃, and 500 ℃ for 10 min. The crystal structure, anisotropic atomic structure, and gasochromic properties of the films were studied. The as deposited and 200 ℃ annealed films are amorphous with lamellar ordering. The films crystallized at the annealing temperature of 300 ℃ and above. The polarized XAS spectra indicate the as deposited VOx film is anisotropy where as the crystallized V₂O₅ thin film is isotropy. The gasochromic reaction become irreversible for the films with crystallized V₂O₅ phase. The irreversible gasochromic reaction is related to a phase transition from V₂O₅ to H_1.43V₂O₅.

In this work Pt nanoparticles on graphene (PtNPs/GN) was formed from graphite oxide (GO) by two-step route. The first step is reduction of GO films by sodium tetrahydridoborate to obtain graphene. Then, the graphene deposited with Pt particles were put in ethylene glycol for a reflux at 120, 150 and 180 °C for 6, 12 and 24 hours, respectively.  

The results show that the electrode catalyst Pt particles have a smaller size and a better distribution on the surface of graphene under the following reducing condition:  reaction time of 24 hours, reaction temperature of 150 °C and the 1.5 g/L of H₂PtCl₆. This PtNPs/GN composites exhibits superior electrochemically active surface area (268 m2/g). For H₂O₂ detection which based on the electrocatalytic reduction of H₂O₂ at the Pt–graphene/GC electrode. The linear range is estimated to be from 0.002 mM to 10 mM  with a high sensitivity (0.238 mAmM^-1cm^-2) and a detection limit of 0.002mM. For glucose detection, The linear range is estimated to be from 0.001mM to 3 mM with a sensitivity of 0.256 mAmM^-1cm^-2.

High dense arrays of three dimensional ZnO nanowires have attracted much attention for applications in nanoscale devices. Dimensionality and size are the two key factors that govern the properties of nanostructures affected by their high surface-to-volume ratio [1]. The requirements for dimensional control, especially of three-dimensional nanowires seem to still be a challenge. Some 3D nanostructural materials have been synthesized. These works have primarily focused on the synthesis of inorganic [2], polymeric nanomaterials [3], and dendrite nanowires [4]. However, exact control for growing multi-dimensional oriented arrays of zinc oxide still remains out of reach. The development of a simple, easily controllable method for growing three-dimensional ZnO nanowires arrays is of great significance. In this study we have successfully synthesized well separated three-dimensional zinc oxide nanowire networks using a Ti-grid assisted thermal evaporation approach. Energy dispersive x-rays spectroscopic (EDS) mapping was used to investigate the scale structure of ZnO nanowire. The formation of three dimensional zinc oxide nanowires are attributed to lattice- diffusion mechanism.

[1] Po-Hsun Shih, Hsuan-Jung Hung, Yuan-Ron Ma, Sheng Yun Wu, Nanoscale Res. Lett. 7(2012) 354.
[2] J. Zhou, Y. Ding, S. Z. Deng, L. Gong L, N. S. Xu, Z. L. Wang, Adv. Mater. 17 (2005) 2107.
[3] M. Srinivasarao, D. Collings, A. Philips, S. Patel, Science 292 (2001) 79.
[4] Y. Zhang, H. Jia, X. Chen, D. Yu, R. Wang, J. Phys. Chem. B 107 (2003) 8289.

Silver is one effective cathode material for solid oxide fuel cells (SOFCs) because of its high oxygen solubility and mobility that offer low oxygen overpotential on solid state electrolytes. However, the highly volatile nature of silver has made it difficult to be a standard cathode material for conventional high temperature SOFC (>700°C). On the other hand, silver can be a good candidate for SOFCs operating at temperatures lower than 500°C, which offers lower material cost with efficient oxygen reaction kinetics. Currently, the application of silver electrode for low temperature SOFCs is few, and the deposition methods are limited to vacuum-based method such as sputtering and evaporation. In this work, we explore the feasibility to use inkjet-printed porous silver as a cathode for low temperature SOFCs. The particle size, porosity, and surface morphology of printed silver electrodes were examined with scanning electron microscopy (SEM). A fuel cell with inkjet-printed silver cathode and Pt paste anode was fabricated, and the cathode polarization and I-V characteristics were measured by a potentiostat to examine the electrode impedance at temperatures below 350°C.

The aluminum oxide (Al₂O₃) films were prepared on silicon substrate by a low temperature liquid phase deposition (LPD) method. The precursor for Al₂O₃ films was aluminum sulfate with crystallized water and sodium bicarbonate. The pH value in the deposition solution plays an important role of Al₂O₃ film. We adjust the concentration of precursor solution and the filter size to control different PH value. The best quality of Al₂O₃ films were obtained at the PH value 3.91 and at the temperature 30℃. The surface morphology and structure are analyzed by Fourier transform infrared spectrum, X-ray diffraction spectrum, electron dispersion spectroscopy, atomic force microscopy and scanning electron microscopy.

Ag/TiO₂ nanocomposite film has attracted much attention since its reversible multicolor photochromic behavior was reported, which relies on reversible spectral hole burning in the particle-plasmon band of the particles.  A wide range of applications for the photochromic Ag/TiO₂ film have been suggested, including a rewritable color copy paper, a multicolor smart glass, a high-density multiwavelength optical memory, and a color-changeable paint.  Simple routes to prepare the film with large area and apparent phenomenon are currently of researchers’ interest.  We studied a sol-gel method to prepare such Ag/TiO₂ nanocomposite film, and investigated the effect of various TiO₂ film structure on its photochromic behavior. We found that the depth of the spectra hole obviously increases when we make the TiO₂ film become porous by adding some Polyethylene glycol (PEG) into the precursor.  In addition, a problem often appearing in such film is that absorption holes are formed not only at the excitation wavelength but also at around 420 nm simultaneously, probably due to anisotropic Ag particles.  We found that this problem can be easily solved by adding certain amount of TiO₂ nanoparticles into the sol.  The findings would be important for controlling the photochromic behavior for the nanocomposite film, and for understanding the roles of the TiO₂ film in the multicolor photochromism.

A simple chemical method/process is described to form a device configuration using planar ZnO nanorod array on commercial printed circuit board. The ZnO NRs in a copper trench electrode forms a metal-semiconductor-metal junction. Various physico-chemical techniques such as XRD, SEM/EDAX, UV-Vis were employed for extensive characterization. The current voltage (I-V) measurements in the dark and under UV illumination were carried out in four-probe contacts to trenched copper electrode. Photo response data in the dark shows non-linear behaviour. Interestingly, upon UV illumination photocurrent increases two orders of magnitude at merely 2 V external bias voltages. We propose that non-linear I-V response and UV photo-switching is mainly due to grain boundary contacts among nano-rod arrays. This device shows stable I-V response in relative humidity ambient between 10-90 %. Details of this work will be presented and discussed in the paper.

ZnO/Al film was fabricated to determine its antifungal activity against Fusarium sp., the causal fungi of crown rot disease of banana. The films were fabricated using electrophoretic deposition and the parameters (i.e. applied voltage, deposition time and sintering temperature) were optimized to obtain a uniform, crack free, and nanoporous film with high surface area. The film that was electrodeposited for 7 mins using an applied voltage of 180V has the most desirable surface. The effect of heat on the morphology of the films was investigated.The film annealed at 300^oC has an average particle size of 185nm, pore size of 147nm and showed good adherence to the Al substrate. This film was used to investigate the photocatalytic activity of ZnO against Fusarium sp. When the ZnO/Al film is exposed to UV, it caused significant delay in the time of infection of the fungi to the banana and decrease in thickness of mycelial growth. Only surface rot on the crown of banana was observed when treated with the ZnO/Al film. This is due to the photocatalytic activity of ZnO film that inhibits the fungi. The findings indicate the viability of ZnO/Al film for treating fungi in banana that cause crown rot disease.

The low-cost mass-production anti-reflective thin film for Si-based solar cells by liquid phase deposition was demonstrated. In this study, titanium oxide films were deposited on 6 inch poly-Si substrate by liquid phase deposition (LPD) with deposition solution of ammonium hexafluoro-titanate and boric acid. The boric acid in the deposition solution can control the deposition rate of titanium oxide film. The average refractive index and reflectance of titanium oxide film were 1.87 and 5.52 % within the wavelength from 400 to 900 nm after annealing. The photovoltaic conversion efficiency of 6 inch poly-Si solar cell with the titanium oxide film as the anti-reflective layer by LPD can reach 15.93 % under standard test conditions.

The solution-type silver nanowire was synthesized by reducing silver nitrate (AgNO₃) with ethylene glycol in the presence of poly(N-vinylpyrrolidone) (PVP). The experimental results show that the different molecular weight of PVP, molar concentration ratio of reactants and the addition rate of silver nitrate will affect the growth characteristics of silver nanowires. Field-emission scanning electron microscopy (FE-SEM), UV-vis spectrophotometer and x-ray diffractometer have been employed to characterize the silver nanowires. As the concentration of silver nitrate reducing, the diameter of the silver nanowires will be thinned to cause a larger aspect ratio. This study successfully prepared silver nanowires with a diameter of 110 nm and a length more than 20 μm. The transmittance and sheet resistance were measured by UV-vis spectrophotometer and four-point probe I-V test, respectively. Finally, the solution-type silver nanowire thin film by the spin coating method shows high transmittance, low sheet resistance and can be used for transparent conductive film.

In this research, zinc oxide thin films were deposited on cleaned glass substrate by spray pyrolysis using zinc acetate dihydrate [Zn(CH₃COO)₂×2H₂O] was as the starting materials to prepare zinc oxide thin films via microwave technique, Microwave technique is a fast, simple, low cost and clean. The different preparative parameters such as the concentration of precursor solution, microwave power and deposition time were investigated. The structure phase composition and morphology of zinc oxide thin films were characterized by X-ray diffraction (XRD) and Field emission electron microscopy (FE-SEM), respectively. Moreover, optical properties of zinc oxide thin films were studied by UV-vis spectrophotometer.

The transparency conductive oxides (TCO) were the important materials in the field of photovoltaic solar cells, liquid crystal displays, sensors and organic light emitting devices. Many of them were produced through sputter and electron-beam depositions. However, a post annealing was needed for the TCO films to achieved a high electrical conductivity. In this study, In₂O₃ thin films grown on glass substrates were fabricated by thermal evaporation via three different deposition procedures. Polycrystalline In₂O₃ films with low resistivity, ranged from 3.8x10^-4 to 9.6 x10^-4 ohm-cm, can be achieved under oxygen ambient without post annealing. For the deposition temperature, T_g, around 100^oC, surface defects with pyramidal shape, due to the aggregation of In atoms, can be observed. For the T_g> 200^oC, the In atoms evaporated out of the In₂O₃ film surface and a smooth In₂O₃ surface was achieved.

Highly textured In₂O₃(111) films with high resistivity, ranged from 3x10^-2 ohm-cm to infinity were obtained by thermal oxidation of In(101) films. The sheet concentration and AFM images suggested that In₂O₃(111) was isolated nanodots for thickness lower than 7nm. The behavior of resistance versus thickness can be well fitted by Namba’s model and was resulted by the scattering of rough surface. The minimization of surface energy of In(101) was the origin of the rough surface. In the third approach, an ultrathin oxidized In(101) seeding layer was deposited prior to the deposition of In₂O₃ film. The observed resistance was around 8x10^-4 ohm-cm. In this method, highly textured In₂O₃(111) films with good conductivity, high transparency and smooth surface were obtained.

Cadmium indium sulfide (CdIn₂S₄), a semiconducting ternary chalcogenide, has been received much attention due to their potential applications in photoconductor, solar cell, light emitting diode (LED). In this research, a simple hydrothermal method for preparation of CdIn₂S₄ with the assistance of L-cysteine, employed as a source of sulfur, was developed for a more environmentally friendly route. This compound was synthesized under different conditions; pH, reaction temperature and time, in order to investigate the effects on purity, crystallinity and microstructure. The products were then characterized by XRD and FT-IR techniques indicating a pure CdIn₂S₄ with a cubic spinel structure at pH 2.8 (initial pH). Based on the SEM and TEM observation, the particles sizes of the CdIn₂S₄ were bipyramid-like in micrometer ranges. Their crystallinities and sizes increased with increasing of reaction temperature and time. EDX spectra of the products showed the existence of Cd, In and S elements and the atomic ratios of the respective elements were closed to the stoichiometry of CdIn₂S₄. The optical properties were also examined by photoluminescence (PL) and UV-Vis spectra.

The coral-like Bi₂S₃ nanostructures were successfully prepared via a simple biomolecule-assisted solvothermal synthesis at 200^oC for 6-72 h. Bismuth nitrate and L-cysteine were used as starting materials. The biomolecule, L-cysteine, was served as a sulfur source and a complexing agent. The products, characterized by powder X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were orthorhombic Bi₂S₃ with a coral-like nanostructure. The crystallinity and the ordered structure of the products were improved when the reaction time was prolonged. The optical band gap of the coral-like Bi₂S₃ nanostructure, calculated from the UV-Vis spectra, was 2.8 eV, indicating a strong blue shift because of the quantum confinement effect.

Recently, a rapid growth in magnetic nanomaterials and devices proceeded because of their wide applications in the Tbit/in² storage, ultrasensitive sensors, magnetic carriers, logic devices and high-frequency devices. The NiFe alloy with an atomic ratio of Ni/Fe around 80/20 is one of the popular materials for studies owing to its low crystalline anisotropy and low magnetostriction. In this study, the permalloy films with different deposition time were prepared on nanoporous anodized aluminum oxide (AAO) templates by the dc magnetron sputtering system. The deposition time (T_d) of the permalloy films was fixed at 60, 120, 180, 360, and 720 s while their corresponding film thicknesses were 12, 24, 36, 72, and 144 nm, respectively.

Needle-like and network structures of the permalloy films on AAO templates can be observed for 120 s£ T_d£ 180 s and T_d≥ 720 s, respectively. These needle-like structures formed at the corner of the AAO substrate rather than in interpore region. The tip diameter and the height of the needle were 28 and 90 nm for T_d= 120 s. While the needle-like structures form, the permalloy displays a perpendicular anisotropy with a small domain size owing to the magnetic shape effect. When the deposition kept continued, an irregular surface composed of nanosized grains was observed. At last, as T_d= 720 s, a predictable 2-dimentional permalloy network manifested itself. For the 2-dimentional permalloy network, the magnetically-easy axis of the permalloy film tends to lie on the film plane with a larger domain size commensurate to the size of the AAO network. The formation of the needle-like structures can be attributed to the large difference in the surface energies between permalloy and aluminum oxide. It can be very reasonable that the Volmer-Weber growth mode takes place during the deposition of permalloy onto the AAO substrate.

In this paper, hydrophobic surface containing different fillers deposited on glass was fabricated using spin coating method. As the filler used inorganic nano powder. They were dispered in ceramic coating solution and different content of theme were used. For increase dispersibility, we applied carbonnanotube in the ceramic coating solution. However, the physics of interactions between CNT and its surrounding matrix material in such nano-composites has yet to be elucidated and methods for determining the parameters controlling interfacial characteristics is still challenging. In this study, an improvement of the physical properties of hydrophobic surface based on filler and CNT.

In recent years, increased interest has been focused on the fabrication of surface-textured silicon nanostructures due to their potential applications in advanced nanoelectronic and photovoltaic devices. Among the various silicon nanostructures, Si nanohole structures have drawn much attention. In this study, we propose a facile and efficient route to fabricate large-area size-and shape-controllable silicon nanohole arrays by using the self-assembled nanosphere lithography in combination with a wet etching technique. Results of SEM examinations clearly demonstrated that excellent controls on the size and spacing of produced Si nanoholes are achieved by adjusting the plasma treatment conditions and the wet etching duration. UV-Vis spectroscopic measurements revealed that the nanohole-structured Si surfaces exhibit strong antireflection properties. The results suggest that the new method proposed in this work may offer great potential for fabricating a variety of Si-based optoelectronic devices without complex lithography.

In the present study Cu₃N/NiTiCu/Si heterostructures were successfully grown using magnetron sputtering technique. The thickness of nanocrystalline Cu₃N was varied from 200 nm to 415 nm and effect of Cu₃N layer thickness on structural, phase transformation, morphological, corrosion and Ni release properties of Cu₃N/NiTiCu/Si heterostructures was studied. The Cu₃N/NiTiCu/Si heterstructure exhibit shape memory effect even after depositing Cu₃N protective layer. Cu₃N(200,305nm)/NiTiCu/Si thin  films  possess low corrosion current density with higher corrosion potential and therefore exhibit better corrosion resistance as compared Cu₃N(415nm)/NiTiCu/Si film. The amount of Ni ions released in SBF solution was not detectable in case of 200, 305nm thin Cu₃N layer but increased significantly on increasing the thickness of Cu₃N layer to 415 nm. Cu₃N(415nm)/NiTiCu/Si heterostructure exibit much reduced corrosion resistance and Ni ion release impeding capability. This can be explained by decrease in adherence of Cu₃N (~415nm) layer on NiTiCu/Si thin film due to its increased thickness. This work is of immense technological importance due to its variety of BioMEMS applications.

Keywords: Thin films,Corrosion,Ni release

Transparent indium zinc oxide (IZO) based semiconductor thin films were deposited on alkali-free glass substrates by sol-gel method and spin coating technique. Comparison of the changes in the optical transmittance and electrical properties of IZO thin films adding different impurity elements (Ga, Zr, and Hf) was discussed in this study. The impurity level was defined by the [M]/[In+Zn], (M=Ga, Zr, or Hf) ratio; it was maintained at 10 at.% in the precursor solutions. Each as-coated sol-gel film was dried at 150 ^oC for 20 min, and then annealed under air ambiance at 500 ^oC for 1 h. XRD examination and TEM analysis confirmed those as-prepared IZO-based thin films had a nanocrystalline phase. In addition, the films exhibited a flat surface (RMS roughness < 0.7 nm) and high optical transparency (T_ave > 89%) in the visible region. Results of Hall effect measurement showed the HIZO thin films had a highest mean resistivity of 1.45×10² Ω with a mean electron concentration of 4.0×10¹⁵ cm^-3 and a mean Hall effect mobility of 10.8 cm²/Vs among all the IZO-based semiconductor thin films.

One-dimensional nanostructured TiO₂ films attract a lot of attention due to their diverse applications in photocatalytic reactions, solar cells, sensor systems, and self-cleaning coatings. Due to the preparation methods are generally complicated, we proposed a simple and fast way to synthesize TiO₂ nanorod/nanowire arrays on a Ti foil under moderate conditions in atmosphere. TiO₂ nanorods/nanowires, 10-100 nm in diameter and 0.2-1.8 um in length depended on reaction conditions, were formed within deposition period of several hours. The formation of the TiO₂ nanorods/nanowires is achieved by the seed growth of nanoparticles on the Ti foil surface from hydrolysis of titanium tetrachloride in nitric acid solution. The morphology, crystal structure, and growth rate of the TiO₂ nanorod/nanowire arrays were affected by reaction temperature, titanium tetrachloride concentration, and nitric acid concentration. Photocurrent measurement was performed to characterize the photoelectrocatalytic activities of the TiO₂ nanorod/nanowire arrays.

Ferromagnetic nickel (Ni) metal nanostructures with controllable morphology and dimensions are of great importance because of both their functionalized properties and potential applications including catalysis, magnetic sensors, magnetic recording media and addressing some basic issues about magnetic phenomena in low-dimensional systems. There are several possible methods of preparing Ni nanostructures. But, according to the massive production needs and the economical aspects, the desired route is the chemical reduction of metal cations from their salt solutions in the presence of a reducing agent. In this present work, morphology controllable synthesis of Ni nanostructures was carried out using hydrazine hydrate (N₂H₅OH) and Ni-salt (NiCl₂•H₂O) in the absence of NaOH and pH buffer, which were mostly used in the reported synthesis procedures. It was observed that the Ni nanostructures with spike, grass and fiber-like morphologies are strongly dependent on the way of synthesis, time of reaction and presence of surfactant. X-ray diffractometer (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were employed to characterize Ni nanostructures with different morphologies. The saturation magnetization (M_s) and coercivity (H_c) value of the Ni nanostructures were very close to the saturation Ms and Hc value of bulk Ni. The structural and microstructural results together with magnetic properties of the nanostructured system clearly show the potential of this technique to obtain morphology controlled property tuning.

As printed and flexible plastic electronic gadgets become increasingly viable today, there is a need to develop materials that suit the fabrication processes involved. Two desirable requirements are solution-processable active materials or precursors and low-temperature processability.

We describe a straightforward method of depositing ZnO films by simple spin coating of an organometallic diethylzinc precursor solution (without involving any synthetic steps) and annealing the resulting film at low temperatures (≤200 °C).1 By controlling the humidity in which annealing is conducted, we are able to adjust the intrinsic doping level and carrier concentration in diethylzinc-derived ZnO. This ability to controllably realize doped ZnO is a key feature of our fabrication process. We employ field-effect measurements as a diagnostic tool to measure doping levels and mobilities in ZnO and demonstrate that doped ZnO with high charge carrier concentration is ideal for solar cell applications. Respectable power conversion efficiencies (up to 4.5%) are achieved in inverted solar cells that incorporate diethylzinc-derived ZnO films as the electron transport layer and organic blends as the active material.

We recently succeeded in extending our approach to ternary oxide films including gallium-zinc oxide (GZO), zinc-tin oxide (ZTO) and aluminum-zinc oxide (AZO) by direct processing of common organo-Ga, -Sn and -Al precursors. Ternary (and also quaternary) oxides are highly valued for their impressive field-effect electron mobilities (mobilities of >50 cm2/Vs have been reported). However, high-performing devices usually require vacuum- and/or high-temperature processing. In comparison, high-performing solution- and low-temperature processed oxides are relatively rare. In this presentation, we highlight the key achievements derived from pristine ZnO and also discuss results achieved thus far from the ternary oxide systems.

Reference:

Foong, T.R.B., Singh, S.P., Sonar, P., Ooi, Z-E, Chan, K.L. and Dodabalapur, A., "Zno Layers for Opto-Electronic Applications from Solution-Based and Low-Temperature Processing of an Organometallic Precursor", J. Mater. Chem., 22, 20896 (2012).

In recent years, oxide-based thin film transistors (TFT) have attracted considerable attention because of their advantageous properties including high optical transparency, low temperature processing, and high electrical performance. Among the various oxide-based TFTs, a-IGZO TFTs are considered as next-generation devices, due to their high field-effect mobility with stable amorphous structure. Meanwhile, a-Si:H TFTs, which are used as conventional switching devices for AMLCDs, become a mature technology having the advantage of good uniformity and low fabrication cost despite of low field-effect mobility. To make low cost and large area display devices, direct printing methods have been investigated for applications of a-Si:H and a-IGZO TFTs. In this study, we report the device properties of a-Si:H and a-IGZO TFTs with inkjet printed copper S/D electrodes. The copper S/D electrodes were formed by inkjet printing with a drop on demand system. By controlling the printing speed and drop spacing, continuous copper S/D electrodes patterns were obtained. The resulting electrical parameters of a-Si:H TFTs with copper S/D electrodes were a saturation field-effect mobility of 0.09 cm2/Vs, a subthrethold slope of 2.02 V/dec, a threthold voltage of 7.27 V and an on/off current ratio greater than 106. On the other hand, a-IGZO TFTs with copper S/D electrodes showed relatively poor electrical performance which are a mobility of 0.004 cm2/Vs, a subthrethold slope of 8.69 V/dec, a threthold voltage of 16.83 V and an on/off current ratio of 7x103. Our results demonstrate the possible application of low cost copper S/D electrodes by inkjet printing technology, which is amenable to make low cost a-based TFTs.

High electrical conductivity (resistivity = 8.5 ´ 10^-4 W cm), optical transparency (> 85%) and gas-permeation barrier performance (water vapor transmission rate ~ 6 ´ 10^-6 g/m² day) on plastic substrates was obtained from uniformly Hf-doped as well as Zr-doped ZnO (HZO or ZZO) films by atomic layer deposition. The uniformity in dopant distribution was realized by utilizing a mixed-deposition ALD cycle to deposit the dopant layers, where a mixed HfO₂/ZnO or ZrO2/ZnO monolayer was deposited by exposing the substrate to an Hf- (or Zr-) and a Zn-containing precursor simultaneously. The mixed dopant layers reduced the lateral dopant concentration in the HZO and ZZO films, eliminating redundant dopant content that can lower doping efficiency and impart insulating property. The effects of dopant distribution on the properties and microstructure of the HZO and ZZO films were analyzed and reported.

Low dimensional nanostructured materials are of great interest due to their unique physical and chemical properties. Among these, zinc oxide (ZnO) is a wide bandgap semiconductor with a wide band gap and large exciton binding energy and possesses several advantages for use in the fabrication of various electronic and photonic devices. ZnO thin films were grown on glass substrate by the thermal evaporation process. The thermal evaporation was done in a horizontal quartz tube furnace which contains a halogen lamp heating system. Commercially available high purity metallic Zn powder (99.9%) and oxygen gas (99.9%) were used as precursors of Zn and oxygen, respectively. After loading the sample, the chamber pressure was reduced to 6 Torr using a rotary vacuum pump. The evaporation process for the growth of ZnO was conducted in the temperature range 550–650 °C for a period of one hour.The crystal phase and crystallinity of the deposited structures were investigated by X-ray diffraction (XRD) patterns measured with Cu-Ka radiation. General morphology of the deposited ZnO thin filmswas observed using field emission scanning electron. The general morphologies of the deposited product were observed by field emission electron microscopy (FESEM) which reveals that the obtained products have wire-like structures and were grown on the substrate at a high density. The nonlinear optical properties of the ZnO thin films have been investigated. The refractive indices in ZnO thin films were measured using a Mach-Zehnder interferometer setup for 532 and 1064 nm wavelengths. The n2 index was obtained from the phase matching SHG measurements. The nonlinear optical properties of the ZnO thin films have been investigated using a Mach-Zehnder interferometer. Studies report that these thin films can be well used for various nonlinear optical applications.

In present investigation conventional hard gelatin capsules were made gastro intestinal tract (GIT) resistant with formalin vapour treatment under optimized conditions. The capsules showed residual formalin content of 100 µg per capsule after 24 hours treatment. In vitro and in vivo GIT resistance of capsule was tested. Small pores (140 ± 20 µm diameter) were drilled formalin hardened shells with CO₂ gas laser for the release of encapsulated theophylline drug. In vitro release of theophylline from these capsules followed zero order kinetics with an initial lag period of 30 to 60 minutes. Drug release variables were also studied. A controlled release capsule of theophylline was attempted consisting of a conventional capsule containing the loading dose and a laser drilled slow release capsule encapsulating the maintenance dose. The prepared dosage form performed satisfactorily under in vitro dissolution as well as in vivo urinary excretion studies.

Nanostructured cadmium oxide (CdO) films were deposited on to thoroughly cleaned glass substrates by reactive dc magnetron sputtering technique. The cathode power, argon and oxygen flow were maintained at 25 W, 20 and 4 sccm respectively. The total working pressure was maintained at 3.8 × 10^-3 mbar. No intentional substrate heating or substrate bias was applied during the growth of the film. The depositions were carried out for different deposition times in order to obtain films with different thicknesses.  The micro-structural, morphology and optical properties of the films were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM) and UV-Visible spectroscopy. The CdO film were polycrystalline in nature with reflection in (111) and (222) planes with a preferential orientation in (111) direction. The lattice constant of the films was about 4.712 Å.  As observed by FE-SEM, the surface morphology of the CdO films was found to be granular in nature with a few agglomerated clusters. The grain size of the films calculated from XRD was about 50 nm which was in good agreement with that of the sizes observed by FE-SEM. The films were transparent and the optical bandgap values of the films deposited for different thicknesses were around 2.5 eV. Further the CdO film was deposited on to interdigitated electrode to be employed as a NH₃ sensor as ammonia (NH₃) gas is one of the most exhaustively studied gases in the field of gas sensors, particularly due to the great demand in agriculture, chemical industries, pharmaceutical, hydrogen fuels, defence and food processing industries. In addition to this NH₃ is the second most widely used chemicals in the world. The Occupational Safety & Health Administration (OSHA) has set Threshold limit (TLV) of 25 ppm for NH₃. The mechanism of NH₃ gas sensing by CdO films was explained by ionsorbed of oxygen species at sensor surface. The fabricated sensor has a capacity to detect the NH₃ down to 50 ppm at a relatively low operating temperature of 150 °C with better response and recovery times. 

Bismuth vandate (BiVO₄) has semiconductor compound with three different phases: monoclinic scheelite type; tetragonal scheelite type and tetragonal zircon type structures and bandgap varying from 2.4 to 2.9 eV. Recently BiVO₄ has proved to be the effective good photocatalyst material. However, the hydrothermal method has been proved to be the most favourable method due to homogenous or heterogeneous chemical reaction through a highly controlled diffusion leading to the formation of designer nanoparticulates having desired size, shape and surface chemistry, especially in the presence of organic ligands, capping agents, chelates, and surface modifiers. In the present work, bismuth nitrate pentahydrate and ammonium vanadate were used as the starting precursors with mole ratio 1:1. Several dopants and surface modifiers (for in situ surface modification) are used in order to alter the band gap and surface chemistry. NH₄OH was used to adjust the pH. The experiments were carried out at 180^oC with autogeneous pressure and experimental duration of 2-8 hours. The resultant products were characterized through various techniques like powder X-ray diffraction, FTIR, SEM, UV-VIS spectroscopy, and photocatalytic properties. BiVO₄ morphology varies depending upon the dopant and the experimental parameters. The photocatalytic efficiency of the products synthesized was tested using textile industrial effluent and virtual dyes like Proclor Red Mx- 5Bdye and Alizarine dye and mixed dyes.

Ever since the invention of magnetic materials, attempts were being made by the research community to tailor the grain sizes and tune the magnetic and optical properties. Nanostructures of nonmagnetic metallic particles like gold, silver etc. are widely studied owing to their versatile applications. However, Such an attempt has never been done in magnetic metal structures. Here elementary nickel nanoparticles are synthesised using a modified reverse micelle process using high oil to water ratio. The nanoparticles thus formed were analysed for their optical properties in order to probe in depth to their band structure modification due to the quantum size limits. Absorption spectra recorded using UV Vis spectrophotometer(PG-T80+ UV Vis spectrometer) for elementary nickel nanoparticles showed semiconducting like behaviour with steps in absorption spectra showing strong quantum confinement signatures. To ensure the quantum confinement, the spectra were charted in higher resolution and the results showed perfect signatures of strong quantum confinement. The metallic nanoparticles formed are magnetic at room temperature. The synthesis of nickel nanoparticles with such strong quantum confinement are reported for the first time which assumes great technological applications including their special applications in transparent magnetic materials based devices. The absorption spectra is shown in Fig.1. The expanded (zoomed) view is provided as the inset.

The CdTe solar cells have a typical device structure of glass/front contact/CdS/CdTe/back contact. Among these layers, the CdTe films work as the absorbers for the CdTe solar cells. In this investigation, the CdS layers were first deposited on the ITO coated glass substrates, and which were followed by the deposition of CdTe layers. A three-electrode electrodeposition system was employed to deposit the CdTe films. The electrolyte for the electrodeposition of CdTe films consisted of chemicals of cadmium sulfate and tellurium dioxide dissolved in the diluted acid solution.

The effects of deposition parameters including the solution temperatures, pH values, and deposition voltages on the properties of CdTe films were investigated. Both of the pH value and deposition temperatures had significant impacts on the CdTe films. In addition, the deposition voltages influenced the stoichiometric ratios and crystalline of as-deposited films.

The chemical bonding and composition of the as-deposited CdTe films were investigated by X-ray photoelectron spectroscopy (XPS) analysis. The depth profiles of XPS binding energy spectra were analyzed to study the composition of near surface and bulk regions of CdTe films. By deconvoluting the cadmium 3d, tellurium 3d, and oxygen 1s binding energy spectra, the results suggested that the as-prepared films contained mostly CdTe and very small amounts of CdO and TeO₂. However, the XRD diffraction patterns of as-deposited films revealed the only preferred orientations of (111), (220), and (311) indicating the crystal structure of CdTe compound, and no diffraction patterns of CdO or TeO2 compounds were observed.

CIGS solar cells are one of the most promising photovoltaic technologies reaching the goals of high efficiency as well as low cost. However, some of the origins affecting the performance of CIGS solar cells are still under investigation. In order to further understand the mechanisms limiting the CIGS device performance, the impacts of substrate temperatures and Se/(In+Ga) ratios during the deposition process on the device performance are carried out. Furthermore, the correlation between the co-evaporation parameters for the preparation of CIGS films and the microstructures of as-deposited CIGS films such as morphology, grain growth, crystallinity, and atomic ratios are thoroughly investigated.

The deposition parameters for the growth of the CIGS absorbers and buffer layers were optimized for the improvement of junction quality and carrier collection of CIGS solar cells. The CIGS films were prepared by the co-evaporation process. The effects of the deposition temperature, deposition time, Se deposition rate, and the incorporation of indium and gallium during the film growth on the morphology, grain growth, and atomic ratios of the resulting CIGS films were investigated.

The deposition temperature was varied for the improvement of Ga diffusion and formation of CIGS films during the deposition. In the three-stage process, the incorporation of gallium and/or indium in the third stage resulted in the formation of a very thin CIGS surface layer on the top of CIGS films leading to the enhancement of junction quality of CIGS solar cells. The high Se flux rate improved the crystallinity of CIGS films. The performance of the CIGS solar cells fabricated with the optimized deposition parameters was analyzed, and thus the correlation between the varied deposition parameters of CIGS films and performance parameters the fabricated CIGS solar cells was established. The efficiency of as-fabricated CIGS solar cells has achieved 17%. 

Titania photocatalysts were successfully synthesized via co precipitation method using Dodecyl amine as a templating agent, and titanium oxosulphate as precursor for titanium. The as-prepared as well as calcined powders were characterized by XRD, SEM/TEM, UV, TG-DTA, FTIR and PL studies. Thermal analysis showed a weight loss of 21 % on heating up to 1000°C in an inert atmosphere. The XRD results indicate that the calcined titania and even as-prepared material have anatase crystal structure with no crystalline imurity phase. Surfactant-free titania nanoparticles with a surface area of 150 m2/g was formed by heat treatment of the as-synthesized matrix at 500°C for 2 h with average crystallite size ~ 8 nm. It was found that the anatase phase of titania was stable up to 850 °C. Excitation of the samples at 300 nm results photoluminescence emission band centered around 467 nm along with other blue emission bands with maxima at ca. 449, 480 and 490 nm, although the PL intensity was much lower. The photocatalyst showed visible light absorption as evident from the UV-VIS spectrum and was found to be an active photo catalyst in sunlight.

Trap-rich CdS nanocrystals were synthesized by employing CdSt2 and sulfur as precursors via a thermal decomposition. Furthermore, X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), absorption and photoluminescence (PL) spectra were used to characterize structure, morphology and luminescence properties of CdS nanocrystals (NCs). CdS NCs have a broad emission across 500-700 nm under the excitation of blue light with 460 nm, consequently, white light can be produced by mixing broad emission from CdS NCs excited by blue light, with the remaining blue light. In addition, the broad emission generation is closely and inseparably related to surface defects. Moreover, LaMer model was used to explain the phenomenon that the intensity of the trap emission gradually decreases as the reaction time increases in contrast with that of the band-edge emission.

Carbon Felts represent a novel material in which to investigate the growth of both photocatalytic thin films and nanoparticles through a variety of methods. They exhibit large surface areas, favourable conductivity and extreme ease of use. As a substrate they are a potentially novel way to enhance any photocatalysis found to originate from a lone photocatalytic material itself. The literature concerning this subject suggests a ‘synergism’ between carbon substrates and the photocatalytic material whereby electron – hole recombination is reduced and also aqueous pollutants are broken down faster due to the adsorption and concentration of  pollutants around the photocatalytic centres.

We have employed several methods of processing this material to act as a support for metal oxide nanomaterials such as Sol-Gel dip coating and Aerosol Assisted Chemical Vapour Deposition (AACVD). SEM confirms the presence of both particles and thin films and these can be controlled by the Sol Gel, withdrawal rate and AACVD precursor Aerosol. XPS and XRD confirm the desired crystal phases are present and successful doping of the carbon felt with the desired species is achieved for the species tested. Photocatalytic testing is to be done to ascertain if the ‘synergism’ reported within the literature can be replicated in these systems.