摘要
Crystal symmetry breaking of wurtzite C 6V 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 E 2 modes reveal violation of the C 6V selection rules. Oppositely, the C 2V configuration satisfies the selection rules for the Raman modes. The observed E 1 and E 2 bands in polarized optical reflection and photoluminescence spectra confirm the anisotropic strain causes the structure change to the orthorhombic one. © 2009 American Institute of Physics.