二維鈣鈦礦於光學非均向性及無濾波片影像偵測器之研究

Abstract

二維鈣鈦礦是一種半導體，由於擁有自然形成的量子阱結構，造成其特殊的光電特性，因此近幾年來已引起許多學者們的注意及研究。在本論文中，對二維鈣鈦礦的研究可分為兩個主要部分。在第一部分中，我們探討二維鈣鈦礦的光學性質。由於二維鈣鈦礦特別的有機物/無機物層狀交疊結構，其在平行及垂直量子阱的方向上具有光學非均向性。除了X射線繞射分析技術，本論文使用一種簡單的非破壞性方法，利用具有可變入射角的偏振光來研究二維鈣鈦礦的光學表現。利用不同偏振入射光的吸收係數比值來定義光學非均向性之大小。接著，使用了光學非均向性來檢測二維鈣鈦礦薄膜的晶體方向一致性。此外，本研究還觀察到光學非均向性的數值大小取決於入射光波長，因為不同入射波長能分別對應到自由載子和激子的吸收。其中最特別的是我們發現了激子的吸收行為幾乎無光學非均向性。 在第二部分中，本論文研究了二維鈣鈦礦在影像偵測器的潛在應用性。通過使用不同的二維鈣鈦礦薄膜材料作為吸收光子能量的半導體，其不同程度的量子侷限效應使得所產生的光偵測器具有顏色選擇性。由於其顯著的光響應會發生在特定波長，我們利用模擬結合了不同的二維鈣鈦礦光偵測器，希望能創造一種新式無濾波片影像偵測器。為了展示模擬的結果，我們利用標準色卡的顏色來做為偵測標準，並將色彩重建結果顯示在簡單的圖案中。 另外，在附錄中，我們研究了碳化矽中的矽空缺。利用測量碳化矽試片在近紅外波長範圍內的光致發光，我們確認了這批以物理氣象沉積法成長的試片具有自然生成之矽空缺。接著，我們將碳化矽晶片的光致發光數據與電阻數據進行比較，推測矽空缺對碳化矽的電性能可能有某種程度影響。

ABSTRACT Two-dimensional (2D) perovskites are attractive materials due to their amazing optoelectronic characteristics, which are resulted from natural quantum well structures. In this thesis, the investigation toward 2D perovskites can be divided into two main parts. In first section, we focus on the intrinsic optical properties of two-dimensional perovskites. Because of the Ruddlesden-Popper phase, 2D perovskites have anisotropic properties in the direction along and across the quantum well. In addition to X-ray diffraction analysis technique, we use a simple and non-destructive method utilizing polarized ultraviolet (UV)-visible light with variable incident angles to calculate the optical anisotropy by measuring the ratio of absorption coefficients from different polarization of incident light. Subsequently, we can use the optical anisotropy to characterize the conformity of crystal orientation of 2D perovskite films. Furthermore, we also discover that the value of optical anisotropy depends on wavelength, which refers to the absorption of free carriers and excitons. In particular, we find that the generation behavior of exciton is almost optically isotropic. In the second part, the potential application of two-dimensional perovskite based photodetectors is studied. By using different 2D perovskites as light absorber, quantum confinement effect makes the produced photodetectors color selective. With the notable photoresponse located at particular wavelength, we model the performance of 2D perovskite-based photodetectors to act as a filter-free image sensor. The simulating results are shown by reconstruction of colors in ColorChecker. In addition, in appendix, we study the intrinsic silicon vacancy in silicon carbide. The intrinsic silicon vacancies of our silicon carbide samples are confirmed by measuring their photoluminescence (PL) in the wavelength of near infrared (NIR) range. The mapping PL data of silicon carbide wafer is taken to compare with the resistance data, and we speculate that silicon vacancies have some impact on electrical performance of silicon carbide.