中文摘要
本論文是以化學氣相傳導法 (Chemical Vapor Transport method，CVT）以碘作為傳導劑成長鈮摻雜之二硒化鎢 (W1-xNbxSe2，x=0, 0.01, 0.05, 0.1, 0.2) 系列單晶以及二碲化鎢(WTe2)和二碲化鉬(MoTe2)層狀材料。
利用XRD 我們發現W1-xNbxSe2(0 ≤ x≤ 0.2 )隨著Nb的摻雜繞射峰會往高角度位移導致晶格常數會遞減且為2H (Two layer hexagonal)結構；並透過電阻率量測發現WSe2半導體會因Nb的參雜變成偏金屬導電性且透過熱電及霍爾量測發現W1-xNbxSe2為退化型P型半導體，且透過拉曼光學量測W1-xNbxSe2隨著Nb的參雜會使E12g=248.17cm-1和A1g=256.85cm-1振動模態往低波數位移。
同時利用XRD我們可以證明二碲化鎢(WTe2)和二碲化鉬(MoTe2)為2H (Two layer hexagonal)結構，且透過電阻量測發現其有高導電度且透過熱電及霍爾量測其材料導電N型半導體特性，並且透過拉曼發現WTe2其厚度變薄會使振動模態A51=161cm-1和A21=212cm-1有增強趨勢且有極化特性，MoTe2其厚度變薄也會使振動模態E2g=234cm-1和B2g=301cm-1有增強趨勢且有極化特性，最後透過壓電調制及穿透 光學我們可以發現二碲化鉬(MoTe2)它為間接能隙且有A、B、C激子躍遷且在室溫間接能隙為0.91 eV而直接能隙為1.06 eV。

關鍵詞: 層狀結構、過渡性金屬硫屬化合物、X射線光電子能譜儀、X-ray晶格繞射分析儀、拉曼散射光譜、調制光譜、電壓-電流量測、霍爾電壓量測、掃描式顯微鏡、穿透式電子顯微鏡、原子力顯微鏡。

Abstract

In this thesis, we have successfully grown W1-xNbxSe2 (Tungsten-doped Niobium diselenides，0 ≤ x≤ 0.2 ) series layered crystals, MoTe2 (molybdenum ditelluride) and WTe2 (Tungsten ditelluride) layer compounds by chemical vapor transport method using I2 as the transport agent.
Using XRD, we find that W1-xNbxSe2 (0 ≤ x ≤ 0.2) with a Nb doping peak shifts to a high angle, resulting in a decrease in the lattice constant and a forming 2H (Two layer hexagonal) structure. Through the resistivity measurement WSe2 semiconductors become metallic and high conductivity due to Nb doping. Thermoelectric and Hall measurements, showed W1-xNbxSe2 is a degenerate P-type semiconductor, and Raman optical measurement revealed W1-xNbxSe2 with Nb impurity displayed E12g and A1g vibration modes shift to lower wave numbers.
At the same time, using XRD, we can prove that WTe2 and MoTe2 are 2H (Two layer hexagonal) structures, and through the resistivity measurement, they are found to be high conductive. The characteristics of conductive N-type semiconductors and the thinning of WTe2 by Raman reveals that the vibration modes A51 = 161cm-1 and A21 = 212cm-1 have a tendency to increase intensity and have a polarization characteristic. The thickness of MoTe2 becomes thinning to make a vibration mode states E2g = 234cm-1 and B2g = 301cm-1 have a tendency to increase intensity and have polarization characteristics. Finally, through piezoelectric modulation and transmittance, we can find that MoTe2 is an indirect semiconductor which has A, B and C excitons. The indirect energy gap at room temperature is 0.91 eV and the direct energy gap is 1.06 eV.
Keywords: Layered structure, Transition metal dichalcogenides , X-ray photoelectron spectrometer, X-ray lattice diffraction analyzer, Raman scattering, modulation spectroscopy, voltage-current measurement, Hall measurement, scanning electron microscope, Transmission electron microscope , an atomic force microscope.

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