B. Karunagaran

Spectroscopic Ellipsometry and Raman Studies on Sputtered TiO2 Thin Films

Titanium dioxide films were deposited using DC magnetron sputtering technique onto silicon substrates at ambient temperature and at an oxygen partial pressure of 7×10 –5 mbar and sputtering pressure (Ar + O2) of 1×10–3 mbar. The composition of the films, analyzed by Auger Electron Spectroscopy (AES), revealed the stoichiometry with an O and Ti ratio of 2.08. The optical constants of the as-deposited TiO2 thin film were determined by Spectroscopic Ellipsometry in the photon energy range 1.2 to 5.5 eV at room temperature. The measured dielectric-function spectra reveal distinct structures at energies of the E1, E1+D1 and E2 critical points due to interband transitions. The Dielectric constant values were found to be substantially lower than those for the bulk TiO2. The dielectric related optical constants, such as the refractive index, extinction coefficient, absorption coefficient and normal incidence of reflectivity are presented and analyzed. The deposited films were calcinated at 673 and 773 K. The influence of post-deposition calcination on the Raman scattering of the films was studied. The existence of Raman active modes A1g, B1g and Eg corresponding to the Raman shifts are reported in this paper. The improvement of crystallinity of the TiO2 films as shown by the Raman scattering studies has also been reported.

Plasma enhanced chemical vapor deposited SiN layers for large area mc-Si solar cell processing

Summary form only given. Surface passivation plays a crucial role in the fabrication process of high efficiency multi-crystalline silicon (mc-Si) solar cells. Plasma enhanced chemical vapor deposition (PECVD) of silicon nitride (SiN) is a proven technique for obtaining layers that meet the needs of surface passivation and anti-reflection coatings. In addition, the deposition process appears to provoke bulk passivation as well due to diffusion of atomic hydrogen. This bulk passivation is an important advantage of PECVD deposition when compared to the conventional CVD techniques. A further advantage of PECVD is that the process takes place at a relatively low temperature of 300/spl deg/C, keeping the total thermal budget of the cell processing to a minimum. This paper deals with the fabrication of multicrystalline silicon solar cells with PECVD SiN layers combined with high-throughput screen printing and RTF firing. Using this sequence we were able to obtain solar cells with an efficiency of 13.5% for multi crystalline polished Si wafers of size 125 mm square. POCl/sub 3/ doped polished silicon wafers with a junction depth of about 0.5 /spl mu/m and an emitter sheet resistance of 35 /spl Omega//sq were selected for the cell fabrication. The mean cell efficiency, fill factor and Voc for the cells prepared in the present study were found to be 13.5%, 0.76 and 0.602 V respectively.

Characterization of vacuum-evaporated In70Se30 thin films

This paper discusses the properties of thermally evaporated polycrystalline In70Se30 thin films (Tsb=303-473K). Structural and surface morphology of the film were identified by X-ray diffractogram and Scanning Electron Microscopy. The composition was verified by EDAX and XPS spectrum. The results of conductivity measurements (Tsb =303K) have revealed that thermionic emission and variable range hopping (VRH) are the two dominant conduction mechanisms in the temperature ranges of (230-280 K) and (170-220 K) respectively.