Observation of enhanced defect emission and excitonic quenching from spherically indented ZnO

The influence of spherical nanoindentation on the band edge and deep level emission of single crystal c-axis ZnO has been studied by cathodoluminescence (CL) spectroscopy and monochromatic imaging. Excitonic emission is quenched at the indent site and defect emission in the range of 450-720 nm is enhanced. Analysis of CL monochromatic images and spectra suggests that at least two different defect states are responsible for the broad defect emission band. Additionally, the indents result in a strong crystallographic dependence of the defect emission, producing a rosette feature with [11 (2) over bar0] [2 (1) over bar(1) over bar0], and [1 (2) over bar 10] orientations that reflect the star-shaped luminescence quenching observed at the excitonic peak (390 nm).