X光激發放光光譜與時間解析X光激發放光光譜觀測氧化鋅與氮化鎵磊晶結構之異常放光現象之研究

Anomalous emission of ZnO and GaN epitaxial structures studied by XEOL and TR-XEOL at TPS X-ray nanoprobe.

吳祐豪(Yu-Hao Wu)

指導教授 ： 李志浩 ； 湯茂竹

國立清華大學/原子科學院/先進光源科技學位學程/碩士(2020年)

摘要

我們在台灣光子源 (Taiwan Photon Source，TPS) 之X-光奈米探測 (X-ray Nanoprobe, XNP) 光束線，量測極化 (polar) 和非極化 (non-polar) 氧化鋅 ( ZnO)以及氮化鎵 (GaN) 之X光激發放光光譜 (X-ray excited optical luminescence, XEOL)和時間解析X光激發放光光譜 (time-resolved X-ray excited optical luminescence, TR-XEOL)，並觀察其特殊放光行為。我們發現，在X光奈米聚焦的照射下，近帶邊緣 (near band edge, NEB) 的放光強度會快速的增強，同時，也發現氮化鎵參雜鎂 (magnesium) 元素後與氧化鎂鋅(MgZnO)在波長325 nm處有特殊放光現象，但此現象在光致發光光譜 (photoluminescence, PL) 量測並沒有被發現。我們推論奈米聚焦的X光可以改善晶體品質，從而提高近帶邊緣的放光強度。此外，我們研究了氧化鎂鋅磊晶薄膜(MgZnO epi-film) c-plane和a-plane的光學特性，並根據不同偏振性 (E⊥c和E∥c) 的X光吸收光譜 (X-ray absorption spectroscopy, XAS) 量測聚焦X光對於晶體結構與原子價電態之影響。我們並藉由台灣光子源的同步輻射加速器的混合運轉模式 (hybrid bunch mode) 進行了時間解析X光激發放光光譜分析，詳細記錄氧化鋅與氮化鎵完整的放光過程，並據以解釋此現象的物理機制。

關鍵字

X光激發放光 ； 時間解析X光激發放光 ； 吸收光譜 ； 光致放光 ； 氧化鋅 ； 氮化鎵

並列摘要

The X-ray excited optical luminescence (XEOL) and time-resolved X-ray excited optical luminescence (TR-XEOL) at 23A X-ray Nanorpobe (XNP) beamline of the Taiwan Photon Source (TPS) were applied to investigate the emission properties of the non-polar and ZnO and GaN epi-films. We found that the emission luminescence of the near-band-edge (NBE) was dramatically enhanced with focused X-ray irradiation time. We also found that the peculiar emission at 325 nm after doping Magnesium element, which was not observed before PL measurement. We attribute to the improved crystal quality been under focused X-ray illumination resulting to enhancement of emission. Furthermore, we studied the optical properties of c-plane and a-plane MgZnO epi-film. According to the crystallographic orientations of E⊥c and E∥c was observed with X-ray absorption spectroscopy (XAS) to observe the effect of crystal structure and valance electron by focused X-ray. The hybrid bunch operational mode of TPS storage ring provides the pulse width of time scale of 30 ps to 310 ns, with which the dynamics of luminescence, namely TR-XEOL is recorded in detailed by a streak camera. Interpretations based on experimental results is provided to explain the physical mechanism under the phenomena.

並列關鍵字

XEOL ； TR-XEOL ； XAS ； PL ； ZnO ； GaN

參考文獻

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