Surface-bound-exciton emission associated with domain interfaces in m-plane ZnO films

Small amount of (10 (1) over bar3)(ZnO) domains were found in the m-plane ZnO films grown on m-sapphire by pulsed laser deposition, which provide strain relaxation of the m-ZnO matrix behaving as a low strain layer. Through carefully correlating low-temperature polarized photoluminescence spectra with the x-ray diffraction peak intensity ratio of (10 (1) over bar3)(ZnO)/(10 (1) over bar0)(ZnO) of the samples grown at different temperature and after thermal treatment, we found that the broad-band emission around 3.17 eV may result from the interface defects trapped excitons at the boundaries between the (10 (1) over bar3)(ZnO) domains and the m-ZnO matrix. The more (10 (1) over bar3)(ZnO) domains in the m-ZnO layer cause the more surface boundary that makes the stronger surface-bound-exciton emission. And the a-axes of both the (10 (1) over bar3)(ZnO) domains and the m-ZnO matrix are aligned with the c-axis of the sapphire (alpha-Al2O3) substrate. The c-axis of the (10 (1) over bar3)(ZnO) domains rotates by about +/- 59 degrees against the common a-axis of the m-ZnO. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732140]