近年來，因應科技快速發展需求，須將半導體元件尺寸微縮化以提升效能，然而傳統半導體材料元件製程面臨其物理極限(如：短通道效應)，因此開啟了二維材料之研究與發展。層狀二維材料因僅具單一原子層厚度，加上層間以凡德瓦力鍵結，表面不具有懸浮鍵，可作為下世代半導體元件之材料。其中，單層過渡金屬硫族化合物(TMDc)相較於石磨烯，具有直接能隙、高吸收度、高量子效率等特性，可響應可見光至紅外光範圍波段，適合發展為二維光電元件。TMDc雖具有較高的光響應，但較長的響應時間限制了在光感測器上的應用，仍需更進一步的釐清與研究，改善製程以提升材料光電表現。
在本研究中，聚焦於分析與探究影響二維材料光電特性之因素。首先透過製程的改善，取得較佳的電子傳輸特性，進而呈現出較佳之光電特性。本研究以633 nm紅光雷射為光源，觀察二硫化鉬電子傳輸特性之變化，並且透過光電流與時間和光功率關係圖，探討量測氣氛、光源、元件偏壓、接觸品質對於材料光電特性之影響，以提升光電衰減速度。本研究亦製作二硫化鉬與石磨烯之異質結構，觀測出光載子於異質接面間之電荷轉移作用，產生永久性光電流，提供更進一步之元件應用。

Recently, as technology has developed rapidly, semiconductor devices are asked to scale down to improve efficiency. However, conventional fabrication processes are encountering their limits (such as “short channel effect”), opening the fields on researches and development of 2D materials. Due to the atomic-layered structures and lack of dangling bonds resulted from interlayer van der Waal forces, 2D materials have become candidates for next-generation devices. Among them, compared with graphene, monolayer TMDc not only reveal direct bandgap, high absorption and high quantum efficiency, but also response to spectrum ranged from visible to NIR , being suitable for 2D optoelectronic devices. While TMDc possess high photoresponsivity, longer response time limit their application for photodetecting. It is necessary to conduct further researches, and modify fabrication processes to improve their performance.
In this work, analysis on the factors that affect optoelectronic properties of TMDc was highlighted. By modifying the processes, better electronic properties were obtained, and then induced better optoelectronic properties. Wavelength 633 nm red laser was used in this work to determine the changes in transport behavior under illumination, and the factors affecting the transport properties, such as atmosphere, light source, bias, and contact quality, were also discussed through time-resolved and power-dependence profiles for improvement of decay speed. Moreover, graphene/MoS2 heterostructures were fabricated, and charges transfer phenomenon across heterojunction was also observed, resulting in persistent photocurrent that provides a platform for further applications.

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