臺灣博碩士論文加值系統

本論文以化學氣相傳導法成長錸的層狀半導體，對此系列晶體進行結構分析，並藉由本實驗室光電量測系統對其特性加以分析研究及討論。
藉由能量質譜儀量測確定成長材料之元素比，穿透式電子顯微鏡確認晶體組成、結構，系列晶體為三斜結構，且為沿﹝001﹞方向堆疊的層狀半導體。光學量測中，利用壓電調制光譜測得二元的ReS2在室溫中有三個躍遷訊號，在低溫下除了E1ex、E2ex外，在1.62 eV後面有三個躍遷訊號且也有著如同E1ex、E2ex的極化特性；ReSe2在室溫訊號較寬，在低溫的時除了E1ex、E2ex外，在1.43 eV有五個能量躍遷，且也有著極化特性，但極化的選擇特性較ReS2差；三元的高硫系列晶體在高階激子則呈現一個較寬訊號。
顯微光激發螢光光譜得知，多層的ReS2在室溫下為兩個寬訊號分別為激子Eex與高階激子ESex，在低溫下Eex分為E1ex、E2ex的，其能量差為34 meV。至於高能量部分也有三個訊號，且有著極化特性，沿著b軸能量較小；垂直b軸能量較大，能量差約為3.5meV，對比壓電調製光譜結果相當符合。ReSe2在低溫量測時，E1ex、E2ex能量差為22.5 meV，且在高階激子部分，得到了三個訊號，同時也有著極化特性，但平行與垂直能量差非常小。
在顯微螢光光譜量測中，我們在ReS2-xSex (0x2)系列的塊材與撕薄樣品中發現差異，在E1ex前，有間接共振訊號，配合AFM的量測，得出厚度越厚，間接共振愈明顯，有2~3個峰值，經由比對過去光穿透的文獻，發現位置相符，對比文獻我們推測其為間接共振所放射的激發螢光訊號。綜合以上，在ReS2-xSex (0x2)系列單晶，有其獨特的極化特性，可應用於微奈米級的極化光電元件，範圍涵蓋近紅外至可見光。

In this thesis, we report an anisotropic optical study of layered ReS2-xSex single crystals grown by Chemical Vapor Transport (CVT). Detailed characterization of the materials were carried out by using energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), piezoreflectance (PzR) spectroscopy, and micro-photoluminescence (μ-PL) techniques.
X-ray and EDX analyses confirmed that the layered ReS2-xSex single crystals are crystallized in the same triclinic structure and approximately in agreement with the nominal starting composition within standard errors. The layered ReS2-xSex series crystallizes in distorted 1T triclinic structure with an obvious c plane. The PzR results show that ReS2 has three transition signals E1ex, E2ex and ESex at room temperature near band edge. At the low temperature, there are three transition signals consisted in the ESex above 1.62 eV in ReS2. The excitons in ESex also show clear polarization dependence like that of E1ex and E2ex. For ReSe2, there are five excitonic transitions near 1.43 eV in ESex at the low temperature (beyond E1ex and E2ex) but they show less polarization dependency with respect to that of ReS2.
The micro-PL results show that mutilayer ReS2 have two broadened peaks at room temperature, Eex and ESex. At 5K, Eex is separated into two peaks E1ex and E2ex, and ESex separated into ES1ex, ES2ex, and ES3ex. All the excitonic emissions ES1ex, ES2ex, and ES3ex show clear polarization dependence, the energy along b-axis is lower and that perpendicular to b-axis is higher. The energy difference between different polarizations in ESex is about 3.5 meV. For ReSe2, we got a broadened PL peak at room temperature. The energy separation between E1ex and E2ex is about 22.5 meV at low temperature. As for the higher series part - ESex, there are also three signals. The energy difference between those of along and perpendicular to b axis is smaller than the energy separation in the ESex of ReS2.
In the micro-PL measurement, we found a spectral difference of the ReS2-xSex series with bulk form and with mutilayer form of thickness t < 70 nm. Below the energy position of E1ex, we can observe several additional peaks referred to the indirect-resonant peaks (I). The I features are enhanced and resonant when the layer thickness is larger than 1 m (bulk) observed by AFM. The energy position of the indirect-resonant emission feature I matched well with that of the indirect absorption edge measured by transmittance. The I feature is hence being defined as the indirect-resonant emission. According to the experimental observations, the series of ReS2-xSex (0x2) single crystals are promising and suitable for fabrication of nano- and micro-scale polarized optoelectronics devices applied in near infrared to visible region.

中文摘要 I
ABSTRACT III
致謝 III
目錄 VI
圖索引 VIII
表索引 XI
第一章 緒論 1
第二章 晶體成長 6
2.1 晶體成長方法簡介 6
2.2 晶體成長設備介紹 8
2.2.1 真空系統 8
2.2.2 長晶反應系統 8
2.3 晶體成長 9
第三章 量測技術 12
3.1 X射線能量散佈分析儀 (EDS) 13
3.2 調制光譜簡介和系統概論 15
3.3 光激發螢光光譜量測 (PL) 19
3.3.1 光激發螢光光譜原理 22
3.3.2 低溫PL實驗方法與系統架構 23
第四章 錸的硫屬系列層狀半導體之光學特性分析 24
4.1 晶格成分比例與結構與型態 24
4.2 場發射穿透式電子顯微鏡影像分析 (FETEM) 26
4.3 調制光譜量測結果分析 29
4.4 光激發螢光量測結果分析 39
4.5壓電調製與顯微光激發螢光比較................................................59
4.6錸的層狀半導體間接共振............................................................63

第五章 結論 65
參考文獻 67

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