Influence of buried interfaces on the charge dynamics in oxide thin films

Abstract

Influence of buried interfaces was investigated in the ZnO thin films grown on Si at 120?C, 150?C, 170?C, and 200?C. by employing PL and SPV. The PL spectrum of samples grown at higher temperatures showed bandgap emission at ~3.3 eV, shallow defects emission ~3.0 eV and visible emission at ~2.4 eV. On the other hand, the visible emission for the sample grown at 120?C visible emission is red-shifted to ~2.1eV. SPV spectra of films grown at higher temperatures in nitrogen gas showed bandgap transition whereas 120?C grown sample only showed weak band transition. Instead one can see transition primarily in IR region due to silicon or silicon oxide. Furthermore, analysis of the transient SPV curves in both nitrogen and vacuum revealed two different characteristic time scales (fast and slow) possibly reflecting contributions of both the ZnO surface and the ZnO/Si buried interface.