Advanced Materials Research Vol. 678

Abstract: Nanocrystalline TiO2 thin films were prepared by sol-gel dip coating method. The structural investigations were carried out using x-ray diffraction technique. Anatase TiO2 thin films with tetragonal phase were obtained and the grain size was observed to lie in the range of 21-25 nm. Analysis on the surface topography of prepared films have been carried out using atomic force microscopy (AFM). The band gap energy is calculated from the absorption spectra of TiO2 films and is found to lie in the range 3.3 to 3.7 eV.

Abstract: Nanocrystalline titanium dioxide (TiO2) thin films have been prepared by dip coating method. The TiO2 thin films have been coated on glass substrate and annealed at 400, 450 and 500° C respectively. The X- ray diffraction pattern shows that TiO2 nanocrystalline thin films are of anatase structure and the grain size is found to be in the range of 20-35 nm. The annealed films have been observed to be nanocrystalline in nature and the crystallinity has been observed to improve on annealing. The surface topography of the films has been studied using atomic force microscope. The optical properties have been studied using transmittance spectra. The band gap has been found to lie in the range of 3.70 to 3.83 eV depending on the annealing temperature.

Abstract: Co doped ZnO samples having composition Zn1-xCoxO (x= 0.00, 0.10 and 0.20) were synthesized by co-precipitation method. X- ray diffraction analysis reveals that the Co doped ZnO nanopowders crystallize in wurtzite structure without any impurity phases. The lattice constants of ZnO nanoparticles decrease slightly with increasing Co concentration. The average grain size of the Co doped ZnO nanopowders are in the range of 33-36 nm. The Williamson – Hall (W-H) analysis used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the pure and Co doped ZnO nanopowders. The results shown that the grain sizes of the samples estimated from the W-H analysis were highly inter-correlated. The strain of the samples was estimated using W-H analysis and it is found that it goes on decreasing with enhancing Co content.

Abstract: Thin films of cuprous oxide are grown on microscope glass slides by chemical bath deposition technique. Molar solutions of copper nitrate, hydrazine and TEA constituted the chemical bath. The depositions are made by optimizing the concentration of precursor solution. X-ray diffraction measurements revealed the phase formation in the oxide films. The optical characteristics of Cu2O films are analyzed by means of UV-Vis-NIR spectrophotometer. The effect of annealing on the structural and optical properties of the film is investigated. The calculated direct optical band gap of the films is in the range of 2.4-1.8 eV.

Abstract: Thin films of Bi_1.5(Sb₂S₃)_0.5 of different thickness were deposited on glass substrate by vacuum thermal evaporation method and annealed at different temperature. The elemental compositions of the films were confirmed by energy dispersive X-ray analysis (EDAX). The prepared films were structurally and morphologically characterized by X-ray diffraction (XRD) and microscopic (SEM & AFM) techniques respectively. It has been confirmed that the films possess polycrystalline nature with orthorhombic phase and the grain size of the films vary from 27.92 to 81.37 nm. The observed bandgap energies (varying from 1.787eV to 1.963 eV) of the films and its temperature dependence were estimated from optical absorption measurements.

Abstract: Abstract. Cadmium Telluride (CdTe) films were thermally evaporated on to glass substrates at room temperature. By varying the amount of source material, thin films of thickness ranging from 90 nm – 635 nm have been prepared. Film of thickness 200 nm was annealed to 400°C for different durations of time and also subjected to alternate heating - cooling cycle. X-ray diffraction study was carried out to study the effect of film thickness, annealing duration and alternate heating-cooling cycle on the structural properties of the films. The transmittance spectra recorded using a UV-Vis-NIR spectrophotometer was used to study the change in optical properties of the films with respect to film thickness, annealing duration and alternate heating-cooling cycle.

Abstract: Lead sulfide (PbS) nanoparticles have been synthesized by photo chemical method and also in the dark ambient at room temperature. The pH of the solution is maintained by adding NaOH. The as-prepared PbS nanoparticles have been characterized by X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive Analysis of X-ray (EDAX) and Transmission Electron Microscopy (TEM). XRD studies reveal the crystalline nature of the particles. Grain size values are calculated using Scherrer’s formula and compared with the standard values. SEM picture shows a flower like structure in the sample synthesized at dark ambient, whereas the samples synthesized in light reveals the presence of varied nanostructures like nanorods, nanowires and nanoparticles. Size of the photo chemically synthesized PbS particles observed from TEM lies between 30nm to 60nm. From EDAX we conclude that the composition is nearly stoichiometric.

Abstract: Indium tin oxide (ITO) thin films exhibiting good transmittance and conductivity suitable for solar cell applications have been prepared on Si(100) and fused silica substrates by optimizing the dc sputtering parameters such as power density and Ar partial pressure. Structural analysis of the as-deposited and annealed ITO films indicated that the as-deposited films are predominantly amorphous, whereas the films annealed at 200–400 °C are found to be of polycrystalline nature exhibiting dominant peaks corresponding to the (222) and (400) planes. The optical transmittance and band gap values of the films are observed to exhibit a change on annealing. From the ellipsometry studies on ITO/Si annealed at 300°C, it is found that graded layer consist of the mixing of two ITO materials with slightly different optical constants and the grading is almost linear. The resistivity of the ITO films is found to decrease with annealing temperature, correlating with the improvement in the crystal quality, and values in the range of 2-3 x10-4 Ω-cm are observed for the films annealed at 300°C. Surface topography study of the films has been performed using atomic force microscope(AFM) and the results are discussed.

Abstract: Cadmium Selenide (CdSe) thin films were pulse electrodeposited at room temperature and at different duty cycles in the range of 6 – 50 % at a current density of 100 mA cm-2. XRD patterns of films deposited at different duty cycles exhibit the cubic structure. The peak widths decreased with increase of duty cycle. The crystallite size increased from 8 to 20 nm. Microstructural parameters like dislocation density and strain were calculated. The transmission spectra exhibit interference fringes. Refractive index calculated by the envelope method varied in the range of 2.5 to 3.3.The optical band gap increased from 1.84 eV to 2.06 eV with increase of duty cycle.

Abstract: Abstract: Alumina (Al2O3) thin films were deposited over glass and Si substrates by DC reactive magnetron sputtering at an oxygen partial pressure of 0.03 Pa. The presence of aluminium and oxygen was confirmed using x-ray photoelectron spectroscopy and the films were found to be nearly stoichiometric or oxygen rich at a sputtering power of 70 W and 60 W, respectively. The as-deposited films were found to be amorphous. Subsequent annealing experiments in vacuum revealed that crystallisation started at 550oC and increased thereafter at higher annealing temperatures for those films deposited at a sputtering power of 70 W. The topography of the as-deposited and annealed films was analyzed by Atomic force microscopy and a progressive increase in the rms roughness of the films was observed with increase in the annealing temperature and the results are discussed