臺灣博碩士論文加值系統

本論文主要探討層狀半導體MoSe2 及WSe2 在各別摻雜錸（Rhenium）元素後，是否改變原本MoSe2 及WSe2 的光學與電學特性。MoSe2 及WSe2 屬於過渡金屬雙硫屬化合物，被歸類為第Ⅵ族，為低能隙反磁性半導體。其單層結構為硫屬複合物與金屬層所形成的三明治結構，層內原子鍵結屬於部分共價鍵與離子鍵混合的形式，層與層之間僅有微弱的凡得瓦（van der Waals）力，晶體結構屬於六角（hexagonal）晶系，a軸等於b軸，但不等於c軸，因而在化學鍵結垂直與平行於層存在著非等向特性。
在單晶成長方面，主要以溴做為傳導劑，利用化學氣相傳導法來成長MoSe2 及WSe2 層狀單晶結構。X-ray繞射量測用來確定所成長的單晶均為六方體結構。光吸收量測結果顯示其為間接能隙半導體，另外利用壓電調制及電解液電場調制光譜來研究MoSe2 及WSe2 在各摻雜Re後的能帶結構。霍爾及電阻率的量測得到在摻雜了Re之後，室溫時的載子濃度、導電率皆上升，載子遷移率則下降。

Molybdenum and Tungsten disulphide belong to the group VIA layer type transition metal dichalcogenides. They are indirect and small band gap diamagnetic semiconductors. These materials exhibit extreme optical and mechanical anisotropy along and perpendicular to the van der Waals plane as a result of the sandwiched interlayer structure, loosely bonded by the weak van der Waals forces. The intralayer bonding is thought to be part ionic and part covalent, with the latter being dominant. Since the band gaps of the materials are well matched to the solar spectrum, they can be used as electrodes in the realization of photoelectrochemical solar cells. In this work, single crystals of MoSe2 and WSe2 doped with Re are grown using the chemical vapor transport method with Br2 as the transporting agent.
X-ray analysis is used to confirm the crystal structure of the as-grown samples. The optical absorption measurements reveal that Re-doped MoSe2 and WSe2 are indirect energy gap semiconductor. The effect of dopants on the interband transition energies of various features has been probed with the assistance of piezoreflectance and polarized EER measurements. Resistivity and Hall measurements have been carried out to study the electrical transport properties of the single crystals. The effect of dopants on the electrical transport and optical properties of MoSe2 and WSe2 layered crystals will be compared and discussed.

目 錄

誌 謝 I
中文摘要 II
英文摘要 III
目 錄 Ⅳ
圖 目 錄 Ⅵ
表 目 錄 Ⅸ
第一章 緒論 01
第二章 MoSe2 與 WSe2 的晶體成長與晶體結構分析 05
2.1單晶的成長 05
2.2 Re-MoSe2 與 Re-WSe2 的晶體結構分析 09
2.2.1 X-ray的實驗原理 09
2.2.2 結果與討論 10
第三章 光特性與電特性的實驗過程 15
3.1 光特性的實驗過程 15
3.1.1 穿透量測 15
3.1.2 調制光譜 19
3.1.2.1 壓電調制反射(PzR) 23
3.1.2.2 電解液電場調制(EER) 24
3.2 霍爾及電阻率實驗 26
第四章 MoSe2 與 WSe2 之光學與電傳導特性研究 32
4.1 MoSe2 與 WSe2 的光吸收量測結果與討論 32
4.2 MoSe2 與 WSe2 的PzR量測結果與討論 39
4.3 EER量測結果與討論 54
4.4 光學特性的結果與討論 56
4.5 霍爾及電阻率量測結果與討論 60
第五章 結論 65
參考文獻 67

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