超快時間解析光譜於氧化鋅結構物之研究

Abstract

氧化鋅屬於寬能隙(約3.37eV)的半導體材料。由於其室溫下具有很大的激子束縛能，約60 meV，使得激子在室溫下具顯著的發光效率。氧化鋅奈米結構已經被應用在發光元件、生醫感測及太陽能電池等領域。另外，微小共振腔中的ZnO奈米結構，可以成為實現室溫 polariton 波思—愛恩斯坦凝聚的最佳選擇。且ZnO具很高的電子遷移率，可成為TiO2以外作為染敏太陽能電池的極佳選擇。因此，研究氧化鋅的載子動力學對太陽能電池和二極體的開發，有關鍵性之影響。 近年來，本研究團隊成功成長 ZnO 薄膜、奈米結構(線、粒與量子點)及氧化鎂鋅量子阱。除了光激發螢光光譜，線性光譜特性，還以 Z-scan 技術量測非線性光學，以及用 pump-probe 探測瞬態吸收行為。在本三年計劃中，我們預計購買脈衝選擇器、光隔離器、自相關干涉儀、高頻鎖相放大器、電控式位移平台、三配頻套件。基於以上經驗從事下列三個研究課題： 一、利用Z軸掃描技術研究氧化鋅的非線性特性；二、利用超寬連續光譜激發-探測技術研究氧化鋅之瞬態吸收光譜；三、利用飛秒時間解析螢光光譜研究氧化鋅奈米結構物。

ZnO is a wide band-gap (Eg~3.37 eV) semiconductor material. Due to the large exciton binding energy of 60 meV, exciton can exist and achieve efficient emission at room temperature. ZnO related materials have been developed to application of photonics, biosensors, and solar cells. In addition, the ZnO-based microcavity is a good candidate to realize the polariton Bose-Einstein Condensate (BEC) at room temperature. ZnO can also be a best choice, except the TiO2, for the use of dye-sensitize solar cell (DSSC) due to its high electron mobility. Thus, it is important to investigate the dynamics in ZnO for the purpose of development in LED and DSSC. Recently, we successfully grow the ZnO thin films, nanostructures (wires, particles and quantum dot) and ZnMgO multi quantum wells. Besides the CW-pumped PL spectrum and linear optical properties, we also investigate the optical nonlinearities via Z-scan method and the transient absorption via pump-probe technique. Base on the experience above, in this three-year project, we plan to purchase and setup the pulse-picker, Faraday isolator, auto-correlator, high frequency lock-in amplifier, electronic controlled linear stage, third harmonic generation Kit, etc. to explore the following subjects: 1. Using Z-scan method to study optical nonlinearities in ZnO. 2. Using super continuum probe beam to study the transient absorption spectroscopy in ZnO. 3. Using femtosecond resolved PL to study dynamics in ZnO nanostructures.