Effect of Aluminium and TIN Oxide Doping on the Structural and Optical Properties of Pulsed Laser Deposited Nanocrystalline Tantalum Oxide Thin Films

Nanocrystalline SnO2 and Al2O3 doped Ta2O5 thin films have been deposited on quartz substrates using reactive pulsed laser deposition. GIXRD studies indicate a phase transition from hexagonal δ- TaO to orthorhombic β-Ta2O5 for SnO2 doped films around a substrate temperature of 773 K whereas the crystallization in the hexagonal δ- TaO phase for the Al2O3 doped films is found to be around 973 K. The preferred orientation is found to be sensitive to a substrate temperature for the SnO2 doped films and is found to change from (0 0 1) to (110) crystal plane of the film deposited at a substrate temperature of 973 K. Micro Raman analysis of SnO2 and Al2O3 doped films show a hardening and disappearance of certain modes which indicates a structural phase transition as confirmed from the GIXRD studies. Al2O3 doping gives rise to an additional mode around 150 cm-1 corresponding to O-Ta-O is bending vibrations in TaO6 octahedra, which is found to be absent in SnO2 doped films. The transmittance of Ta2O5 films deposited at 300 K is found to decrease up on SnO2 doping and increase up on Al2O3 doping compared with the undoped film and decreases with the increase in substrate temperature for both dopants.