Influence of the Iron as a Dopant on the Refractive Index of WO3

Results on studies of pure tungsten oxide WO3 and 2, 3 and 4% Fe-doped WO3 grown on the sapphire substrates by reactive pulsed laser deposition technique are reported. From X-ray diffraction it results that the crystalline structures changed with the substrate temperature and the peaks diffraction having a small shift by the amount of Fe content in WO3 lattice was noticed. Scanning electron microscopy presented a random behavior of WO3 nanocrystallites size with substrate temperatures. In the presence of 2% Fe-doped WO3, the nanocrystallites size varied gradually from 60 nm to 190 nm as substrate temperature increased. The transmission spectra of the pure and 2, 3 and 4% Fe-doped WO3 films were obtained within the 300–1200 nm spectral range. The refractive index of WO3 and Fe-doped WO3 layers were calculated by the Swanepoel method. The refractive index of pure WO3 shows a variation from 2.35–1.90 and for 2% Fe-doped WO3 from 2.30–2.00, as the substrate temperature increased. The contents of 3 and 4% Fe-doped WO3 presented nearly identical values of the refractive index with pure and 2% Fe-doped WO3, in error limits, at 600 °C. The optical band gap changes with substrate temperature from 3.2 eV to 2.9 eV for pure WO3 and has a small variation with the Fe.

Optical properties of CdS/CdTe heterojunction prepared by physical vapor deposition technique

The paper presents the study of the optical properties of a thin layer of Cadmium Sulphide deposited on Cadmium Telluride films. CdTe thin films were obtained by vapor phase condensation method using different technological factors, in particular, different thickness (different time of deposition τ) on glass substrates. After deposition the optical properties were analysed by Swanepoel method, using transmission spectra. The upper thin layer of CdS was deposited by thermal evaporation method on CdTe thin films. The change in optical properties of CdS/CdTe heterojunction in comparison with CdTe thin films was investigated. Using a Swanepoel method were calculated the main optical constants, such as refractive index, absorption coefficient and optical conductivity. By this method the thickness of the thin film was determined and compared with the experimental values obtained by the profilometer.

Structural and Optical Properties of Anatase-TiO2 Sputtered Nano-Thin Films

Titanium dioxide (TiO2) nanothin films were deposited on unheated substrate, the glass slide and Si-wafer, by DC reactive magnetron sputtering with different substrate-target distance (dst), in range of 8 to 14 cm. The structural, surface morphology and transmittance spectrum of TiO2thin films were characterized by grazing-incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM) and spectrophotometer, respectively. XRD results show that as-deposited TiO2films with short substrate-target distance have only anatase crystal structure corresponding to the anatase in (101) and (200) plane, and turn to be amorphous with long substrate-target distance. The thickness and roughness varied from 50 nm to 142 nm and 1.6 nm to 3.5 nm, respectively. The as-deposited TiO2films exhibited high visible transmittance. The optical constants of the films, refractive index (n) and extinction coefficient (k), were calculated by Swanepoel method, at 550 nm, was about 2.43 - 2.76 and 0.082 - 0.187, respectively. The energy band gap (Eg) of the as-deposited TiO2films in the range of 3.20 - 3.25 was observed.