Crystal symmetry breaking of wurtzite C6V to orthorhombic C 2V due to in-plane anisotropic strain was investigated for nonpolar (112̄0) ZnO epifilms grown on the R -sapphire. X-ray diffraction results reveal the epilayer is subjected to a compressive strain along the polar c -axis and tensile strains along both a- [112̄0] surface normal and in-plane p- [11̄00] axis. The polarized Raman spectra of E2 modes reveal violation of the C6V selection rules. Oppositely, the C2V configuration satisfies the selection rules for the Raman modes. The observed E1 and E2 bands in polarized optical reflection and photoluminescence spectra confirm the anisotropic strain causes the structure change to the orthorhombic one.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)