Avinash Rokade

Hydrogenated Silicon Carbide Thin Films Prepared with High Deposition Rate by Hot Wire Chemical Vapor Deposition Method

Structural, optical, and electrical properties of hydrogenated silicon carbide (SiC:H) films, deposited from silane (SiH4) and methane (CH4) gas mixture by HW-CVD method, were investigated. Film properties are carefully and systematically studied as function of deposition pressure which is varied between 200 mTorr and 500 mTorr. The deposition rate is found to be reasonably high (9.4 nm/s 15.54 nm/s). Formation of SiC:H films is confirmed by FTIR, Raman, and XPS analysis. XRD and Raman analysis revealed that with increasing deposition pressure amorphization occurs in SiC:H films. FTIR spectroscopy analysis shows that bond density of C–H decreases while Si–C and Si–H bond densities increase with increasing deposition pressure. Total hydrogen content increases with increasing deposition pressure and was found to be <20 at.%. The absence of band ~1300–1600 cm−1 in the Raman spectra implies negligible C–C bond concentration and formation of nearly stoichiometric SiC:H films. The band gap shows increasing trend with increasing deposition pressure. The high value of Urbach energy suggests increased structural disorder in SiC:H films. Finally, it has been concluded that CH4 can be used as effective carbon source in HW-CVD method to prepare stoichiometric SiC:H films.

Substrate temperature dependent studies on properties of chemical spray pyrolysis deposited CdS thin films for solar cell applications

Thin films of CdS have been prepared by chemical spray pyrolysis by spraying precursor solution directly onto soda lime glass (SLG) substrates. Influence of substrate temperature on structural, optical, morphological and electrical properties have been investigated by using various techniques such as low angle X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), UV–visible spectroscopy photoluminescence (PL) spectroscopy etc. Formation of CdS has been confirmed by low angle XRD, Raman spectroscopy and XPS analysis. XRD pattern showed that CdS films are polycrystalline, have hexagonal structure and prefer orientation of crystallites shifts from (101) to (002) with increase in substrate temperature. Raman spectroscopy revealed that exciton-phonon coupling depends on substrate temperature and hence on crystallite size. Optical band gap increased from 2.43 to 2.99 eV when substrate temperature increased from 325 to . Transmittance of the film also showed an increasing trend from to with increase in substrate temperature. Such high band gap and transmittance values of CdS films prepared at make it a useful window material in CdS/CdTe and CdS/Cu2S heterojunction solar cells.

Synthesis and Characterization of Molybdenum Back Contact Using Direct Current-Magnetron Sputtering for Thin Film Solar Cells

In present work, we report synthesis of Mo thin films by DC-magnetron sputtering method. The structural, optical, morphological and electrical properties were investigated as a function of target-to-substrate distance. From the results, it is evident that with increase in target-to-substrate distance the thickness of films decreases while its sheet resistance and electrical resistivity increases, which is confirmed by van der Pauw method. Low angle XRD analysis revealed that with increase in target-to-substrate distance preferred orientation of Mo crystallites changes from (211) to (110) and its size decreases. The FE-SEM analysis revealed a significant change in surface morphology with increase in target-to-substrate distance. UV-Visible spectroscopy analysis showed that Mo films deposited at high target-to-substrate distance have more reflection than those deposited at lower target-to-substrate. Finally, adhesion test was performed using scotch hatch tape adhesion test which show all Mo films have excellent adhesion over the entire range of target-to-substrate distance studied. The employment of such Mo films as back contact can be useful to improve efficiency of CZTS solar cells.

Sustainable Energy Harvesting Using Efficient α-Fe 2 O 3 Photoanode Through Photocatalytic Water Splitting Using Facile Chemical Route

Here, a simple, controlled and cost effective electrodeposition technique was used to synthesize α-Fe2O3 hematite photo-electrode for solar water splitting. We have synthesized thin films of α-Fe2O3 by varying electrodeposition potential from −0.2 to 0 V at optimum conditions of cycles by using potentiostat. The obtained ferrihydrite thin films were transformed into α-Fe2O3 thin films by annealing them at 600 °C for 1 h. Films were investigated by XRD, SEM, UV-Visible and Raman spectroscopy for their structural, optical and morphological properties. Further suitability of α-Fe2O3 thin films as a photo-electrode has been evaluated by photoelectrochemical (PEC) measurements which exhibited photocurrent density of 65 µA/cm2 at 0.5 V versus SCE under AM 1.5 100 mW/cm2 illumination. The effective enhancement in photocurrent conversion efficiency with optimum film thickness has been observed upon light irradiation. The absorption spectrum of the α-Fe2O3 shows significant absorption in the visible region. However, photo-conversion efficiency is quite low. The obtained results suggest that the well controlled thick α-Fe2O3 material can be utilized as a shell layer with wide band gap nano-structured semiconductor like ZnO, TiO2 to form hetero-structure for solar water splitting application.