本論文使用兩種不同的二維材料之過渡金屬硫屬化合物MoS2與WSe2做異質接面的結合並進行探討其接面特性. 本論文以熱化學氣相沉積法方式, 利用固定比例的三氧化鎢與硒粉末, 三氧化鉬與硫粉末成長WSe2與MoS2於藍寶石基板上, 分別以光學顯微鏡, 拉曼光譜儀, 光激螢光光譜, X射線光電子能譜學及掃瞄式電子顯微鏡進行分析此材料之樣品大小, 形貌, 能隙大小, 薄膜層數及元素構成. 在場效電晶體電壓-電流特性量測中以曲線最低點所落的位置判斷出二硒化鎢為 p 型半導體材料而二硫化鉬為 n 型半導體材料. 本論文以控制成長位置的方法, 在大面積的二硒化鎢上直接沉積二硫化鉬, 成功地製作異質接面二極體元件, 在進行電性量測後發現到此異質接面有明顯的整流效果. 將結果進一步變化, 製備出三端的pnp異質接面, 在電壓-電流特性曲線量測中得到其操作行為與一般的電晶體相似, 能得到其飽和區與工作區的範圍, 最後在應用於開關電路.

In this study, we demonstrated the characteristic and synthesis of heterojunction which was consisted of p-type tungsten diselenide (WSe2) and n-type molybdenum disulfide (MoS2). We used chemical vapor deposition (CVD) method to synthesize WSe2 and MoS2 on sapphire substrate. Optical microscope (OM) and scanning electron microscope (SEM) image was used to examine the morphology of thin films. Raman spectroscopy, photoluminescence spectroscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscope (XPS) indicated the thickness, band gap energy and the elements composition of the as-prepared WSe2 and MoS2 samples. We showed electrical property of WSe2 and MoS2 transistors, WSe2 was typical of field effect transistor (FET) devices with p-type channel, and MoS2 was typical of FET devices with n-type channel. In order to fabricate the pn heterojunction diode, WSe2 was grown in the first step, followed by MoS2 CVD growth on the top surface of WSe2. In the voltage-current characteristic measurement, we demonstrated a clear current rectification behavior in the MoS2/WSe2 heterojunction diode, and the turn-on voltage was 0.5 V. Finally, we demonstrated the pnp heterojunction based on WSe2/MoS2/WSe2. The collector current increased as the base current became smaller. Compared to traditional bipolar junction transistor (BJT), we can find out the saturation region and the active region in the voltage-current plot. Therefore, we applied the pnp heterojunction to the switch circuit, we expect the heterojunction can be widely applied to the optoelectronic devices.

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