Microstructure and Optical Properties of Rare-earth Doped ZnO Thin Films

Yttrium doped Zinc Oxide (YZO) thin films are deposited by Pulsed Laser Deposition on silicon (1 0 0) substrates at temperature of 300 °C and oxygen at 0.7 mbar. X-ray Diffraction (XRD) of in situ annealed films shows epitaxial growth of YZO films along ZnO (0 0 2) plane and Y2O3 (4 2 2) plane. Y2O3 is observed in ZnO films doped with 3-5 wt.% of Y2O3. Raman Spectroscopic analysis shows shift in vibration modes associated with ZnO due to yttrium addition. Dense columnar growth is observed in the scanning electron micrographs of YZO films. The optical band gap of ZnO is randomly red shifted in a range 2.83-3.28 eV by increasing Y doping level. All the YZO films show high transparency in visible region. These YZO thin films can be used in optoelectronic devices like solar cells, thin film transistors etc.