Peculiar near-band-edge emission of polar and non-polar ZnO and MgZnO epi-films studied by synchrotron-based XEOL and TR-XEOL
Yu Hao Wu2,1*, Bi-Hsuan Lin1, Xiao-Yun Li1, Wei-Rein Liu1, Chih-Hao Lee2, Mau-Tsu Tang1,2, Wen-Feng Hsieh3
1National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
2Department of Engineeing and System Science, National Tsing Hua University, Hsinchu 30076, Taiwan
3Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30076, Taiwan
* Presenter:Yu Hao Wu,
The synchrotron-based X-ray excited optical luminescence (XEOL) at the Taiwan Photon Source (TPS) X-ray Nanoprobe (XNP) beamline was applied to investigate the optical properties of c- and a-plane MgZnO epi-films. Peculiar phenomenon was found after steeply focused X-ray irradiation, that the emission luminescence was dramatically enhanced more than 10 times at the near-band-edge (NBE) of the MgZnO epi-films of both planes. As reported in our previous works, the polarization-dependent X-ray absorption spectroscopy (XAS) with E⊥c and E∥c was used to characterize the crystallographic orientations. In addition, after X-ray irradiation, the MgZnO epi-films appeared an anomalous emission at 325nm, which was not observed in ZnO epi-films before. We attribute that the high peak power density of the X-ray nanobeam may give rise to the anomalous excitation relative to the Mg energy states. The dynamic details of various emission process observed by time-resolved XEOL (TR-EXOL) will also be reported.

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