Structural degradation and optical property of nanocrystalline ZnO films grown on Si (100)

Structural degradation of nanocrystalline ZnO films was observed with an increase in films thickness. Nanocrystalline epitaxial thin film with thickness of similar to 170 nm changed to polycrystalline similar to 900 nm with an increase in deposition time. Surface morphology revealed an average grain size of 30-50 nm. Spatial correlation model indicated structural disorder due to relative disorientation of crystalline phases at nanoscale. The photoluminescence spectra showed free exciton (FX) similar to 3.31 eV, donor bound-exciton (D(o)X) similar to 3.26 and donor-acceptor-pair (DAP) similar to 3.22 eV for thin films, which redshift, i.e., FX similar to 3.30, D(o)X similar to 3.24 eV, and DAP similar to 3.19-3.17 eV for thicker films (400-900 nm). (c) 2008 American Institute of Physics.