Probing the anomalous emission of polar and non-polar ZnO and MgZnO epi-films via XEOL and TR-XEOL
Yu Hao Wu1,2*, Bi Hsuan Lin2, Yung Chi Wu2, Wei Rein Liu2, Chien Yu Lee2, Bo Yi Chen2, Gung Chian Yin2, E Wen Huang1, Chih Hao Lee3, Mau Tsu Tang2, Wen Feng Hsieh4
1Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
3Department of Engineeing and System Science, National Tsing Hua University, Hsinchu 30076, Taiwan
4Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
* Presenter:Yu Hao Wu,
The X-ray excited optical luminescence (XEOL) and time-resolved XEOL (TR-XEOL) at 23A X-ray Nanoprobe (XNP) beamline of the Taiwan Photon Source (TPS) were applied to investigate the emission properties of the polar and non-polar ZnO and MgZnO epi-films. Operating in the hybrid bunch mode provides not only a sufficiently high peak power density but also high-quality temporal domain measurements for studying the luminescence dynamics of the samples. Based these features, we found the anomalous emission behavior of the as-grown and rapid thermal annealing (RTA)-treated a-plane MgZnO epi-films, from which a peculiar emission was observed at ∼325 nm, along with a rapid increase in near-band edge (NBE) emission with increasing X-ray irradiation time. This peculiar emission behavior was also observed in the cathodoluminescence spectra obtained under electron beam excitation. We suggest the anomalous emission is caused by the defect color center of Mg-related energy states (MgZnO film) or F+ center (sapphire wafer) created by the high-dose X-ray or electron beam irradiation. Detailed results of the experiments and the physical mechanism will be discussed.

Keywords: X-ray excited optical luminescence (XEOL), MgZnO film, X-ray absorption spectroscopy (XAS), Nanoprobe, synchrotron light source