Effect of Mn doping on the structural,morphological, optical and magnetic properties of indium tin oxide films

We report on the preparation and characterization of high purity manganese (3–9 wt.%) doped indium tin oxide (ITO, In:Sn = 90:10) films deposited by sol–gel mediated dip coating. X-ray diffraction and selected area electron diffraction showed high phase purity cubic In₂O₃ and indicated a contraction of the lattice with Mn doping. High-resolution transmission electron microscopy depicted a uniform distribution of ∼20 nm sized independent particles and particle induced x-ray emission studies confirmed the actual Mn ion concentration. UV-Vis diffuse reflectance measurements showed band gap energy of 3.75 eV and a high degree of optical transparency (90%) in the 100–500 nm thick ITO films. X-ray photoelectron spectroscopy core level binding energies for In 3d_5/2 (443.6 eV), Sn 3d_5/2 (485.6 eV) and Mn 2p_3/2 (640.2 eV) indicated the In³⁺, Sn⁴⁺ and Mn²⁺ oxidation states. Magnetic hysteresis loops recorded at 300 K yield a coercivity H_c ∼ 80 Oe and saturation magnetization M_s ∼ 0.39 μ_B/Mn²⁺ ion. High-temperature magnetometry showed a Curie temperature T _c > 600 K for the 3.2% Mn doped ITO film.     

Optimized Li4Ti5O12 nanoparticles by solvothermal route for Li-ion batteries

Li4Ti5O12 (LTO) nanoparticles were successfully synthesized by solvothermal technique using cost-effective precursors in polyol medium and post-annealed at temperatures of 400, 500, and 600 degrees C. The XRD patterns of the samples were clearly indexed to the spinel shaped Li4Ti5O12 (space group, Fd-3 m). The particle size and morphology of samples were identified using field-emission SEM. The electrochemical performance of solvothermal samples revealed fairly high initial discharge/charge specific capacities in the range 230-235 and 170-190 mAh/g, at 1 C-rate, while that registered for the solid-state sample has been 160 and 150 mAh/g, respectively. Furthermore, among these samples, LTO annealed at 500 degrees C exhibited highly improved rate performances at C-rates as high as 30 and 60 C. This was attributed to the achievement of small particle sizes with high crystallinity in nano-scale dimensions and hence shorter diffusion paths combined with larger contact area at the electrode/electrolyte interface.     

CuInS2/In2S3 thin film solar cell using spray pyrolysis technique having 9.5% efficiency

Copper indium sulfide (CuInS₂)/In₂S₃ solar cells were fabricated using spray pyrolysis method and high short circuit current density and moderate open circuit voltage were obtained by adjusting the condition of deposition and thickness of both the layers. Consequently, a relatively high efficiency of 9.5% (active area) was obtained without any anti-reflection coating. The cell structure was ITO/CuInS₂/In₂S₃/Ag. We avoided the usual cyanide etching and CdS buffer layer, both toxic, for the fabrication of the cell.     

Influence of the thickness on structural, optical and electrical properties of chemical bath deposited CdS thin films

Cadmium sulfide films of different thicknesses were deposited by chemical bath deposition (CBD) from a bath containing cadmium acetate, ammonium acetate, thiourea, and ammonium hydroxide. The XRD patterns show that the films are of hexagonal phase with preferred (0 0 2) orientation and the grain size increases with the thickness of the film. The band gap of the films was calculated from the transmittance data and it was found that the band gap decreases as the film grows in thickness. The photo-response studies indicate that the film thickness has an influence on the current decay under dark. The observed opto-electronic properties were attributed to the crystallite size and internal microstrain.     

CdTe/CdS Solar cells on flexible molybdenum substrates

Development of CdTe/CdS solar cells on flexible metallic substrates is highly interesting due to the light weight and flexible nature of the solar modules. We have deposited CdTe films onto flexible molybdenum substrates using close-spaced sublimation technique and the CdTe/CdS junction was developed by depositing a thin layer of CdS onto the CdTe substrate from a chemical bath. The devices were characterized by Current–voltage (I–V) and photocurrent spectroscopy techniques. Prior to the deposition of the transparent conducting layer, the devices were annealed in air at different temperatures and found that the devices annealed at 400°C have better photovoltaic parameters. The efficiency of a typical device under 60 mW cm⁻² illumination was estimated as 3.5%.     

Plasma Polymerization Surface Modification of Carbon Black and its Effect in Elastomers

Surface modification of carbon black by plasma polymerization was aimed to reduce its surface energy in order to compatibilize the filler with various elastomers. A fullerenic carbon black was used for the modification process. Thermogravimetric analysis, wetting behavior with liquids of known surface tension, TEM and TOF‐SIMS were used to characterize the carbon black before and after modification. The state of plasma‐coated carbon black in rubber was studied by means of conductivity measurements. The behavior of the modified filler in rubber was studied using the Payne effect and stress/strain properties. The study shows that plasma‐coated carbon black results in a better dispersion in different rubber systems than the uncoated version.

     

Effect of temperature and electron irradiation on the I–V characteristics of Au/CdTe Schottky diodes

The results of the studies on the effect of temperature and 8 MeV electron irradiation on the current–voltage (I–V) characteristics of the Au/CdTe Schottky diodes are presented in this article. Schottky diodes were prepared by evaporating Au onto n-type CdTe films electrodeposited onto stainless steel substrates. The forward and reverse current–voltage characteristics of these diodes were studied as a function of temperature. The diodes were subjected to 8 MeV electron irradiation at various doses and their effect on the I–V characteristics was studied. Some intrinsic and contact properties such as barrier height, ideality factor, and series resistance were calculated from the I–V characteristics. Diode ideality factor of the junctions were greater than unity. The ideality factor and the series resistance R_s increase with decrease in temperature. The conduction seems to be predominantly due to thermionic emission–diffusion mechanism. The resistance was found to increase with increasing dose. The leakage current, ideality factor and barrier height were found to be unaffected by electron irradiation up to, a dose of about 40 kGy.     

Spectroscopic ellipsometry investigation of optical and interface properties of CdTe films deposited on metal foils

Optical and interface properties of the CdTe films electrodeposited on Molybdenum and Stainless Steel substrates were investigated using variable angle spectroscopic ellipsometer measurement and multilayer optical analysis. The refractive index of CdTe film obtained from the multilayer optical modeling is found to be lower than single crystal data. The Bruggeman effective medium analysis shows that the films consist of nearly 11% void due to poor crystallinity resulting in the lower refractive index. The multilayer optical model also indicates the presence of a Te rich interface between CdTe and substrate, which can be associated to the kinetics of CdTe electrodeposition that starts from nucleating Te on substrate surface followed by the formation of CdTe.     

Dielectric and conduction studies on hot-wall deposited CdSe films

CdSe films are deposited using hot-wall deposition technique on glass and ITO substrates. From the XRD analysis, the structural parameters like crystallite size, dislocation density and strain were calculated. Films had preferential orientation along (0 0 2) and the structure of the film corresponded to wurtzite nature. From the EDAX analysis a slight increase in the cadmium content is observed as thickness increases. The dielectric study has been carried out on the stoichiometric films at different frequencies and temperatures to study their effect on capacitance, dielectric constant and dielectric loss. To explore the effect of illumination on these fundamental dielectric parameters, measurements are taken in dark as well as under an illumination of 1000 lx. and observed slight variation in these parameters. The temperature coefficient of capacitance, relative permittivity and linear expansion coefficient are evaluated. From the AC conduction studies the conduction was found to be due to hopping. Variation of conductivity with temperature reveals the presence of two activation energies. The Mott–Schottky plot for the films yields the value for carrier concentration in the range 10¹⁷–10¹⁸ cm⁻³ and the conduction was found to be n-type.