二維材料如今受到非常多的矚目, 特別是物理結構特性以及電性傳輸特性. 本研究將同樣為二維材料的石墨烯與不同比例成分之三元化合物W(SxSe(1-x))2製作成異質結構, 具有成分變化的W(SxSe(1-x))2使用化學氣相傳輸法而長成, 並使用X射線能量散佈光譜儀表面分析確定其元素比例含量, 透過精算莫爾數比例有效地控制材料晶體成分比例, 利用拉曼光譜儀了解硫硒比例的改變觀察其振動模態的變化, 再設置電晶體量測得到隨硫的比例含量增加會使得材料轉變成n型材料. 另外, 石墨烯為一個零能隙半導體, 本研究的石墨烯是利用銅箔經由化學氣相沉積法成長, 並且利用高解析電子顯微及拉曼光譜儀判斷石墨烯的厚度及層數, 在使用X射線電子能譜儀進一步確定吸附氧分子含量, 並製作成電晶體觀察石墨烯吸附氧氣而調變成為p型的半導體材料. 最後兩材料利用凡得瓦力的疊合成異質結構. 而Graphene/WS1.2Se0.8, Graphene/WS1.6Se0.4及Graphene/WS2為pn接面現象. 塊材的 W(SxSe(1-x))2隨硫成分增加, 與石墨烯堆疊可得知為pp異質接面轉變成pn接面, 這一系列塊材的調變期待可應用到不同領域的元件, 例如整流元件, 電晶體, 或者光電元件等等.

Two-dimensional (2D) materials have attracted much attention nowadays due to their physical and electrical properties. In this study, tungsten sulphoselenide (W(SxSe(1-x))2) materials of the ternary compounds were stacked with graphene, like W(SxSe(1-x))2, which is also a two-dimensional material. The W(SxSe(1-x))2 materials were formed by using chemical vapor transport (CVT) with chemical ingredients varied with sulfur / Selenium ratios. The elemental proportions of the tungsten sulphoselenide materials were confirmed by energy dispersive spectroscopy (EDS). These results indicated that the crystals could be modulated by adjusting the molar ratios of reactants (W/S/Se) accurately. Phonon vibration modes were monitored and analyzed by using Raman spectroscopy. The WS2-like A1g mode was red-shifted with decreasing sulfur content. In the field-effect transistor (FET) measurement of W(SxSe(1-x))2 materials, WSe2 (x=0) was a p-type semiconductor while WS2 (x=1) was a n-type semiconductor. The properties of W(SxSe(1-x))2 series materials were modified from p-type to n-type with sulfur content. The pristine graphene was grown by the chemical vapor deposition (CVD) system was a p-type semiconductor due to oxygen absorption from the air. The number of layers and property of graphene were examined by TEM microscopy and Raman scattering alternately. Then, the W(SxSe(1-x))2 materials which stacked with graphene formed heterojunctions through van der Waals force. Composition-related characteristics were examined throughout the heterostructures in the electrical experiment. With the increasing content of sulfur, the W(SxSe(1-x))2 materials with graphene were modulated from pp to pn heterojunction. The graphene/WS0.8Se1.2, graphene/WS1.6Se0.4, and graphene/WS2 heterostructures were all pn junctions. The more sulfur content in W(SxSe(1-x))2 of pn heterojunctions increased, the higher threshold voltages raised. Therefore, there is great potential in heterojunction-applications in the future, such as rectifiers, transistors, and optoelectronic sensors.

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