高偵測性二硫化鉬於圖案化藍寶石基板上之氣體與光交互作用與分析

Abstract

近年來二維材料得到了許多研究團隊的重視，不少研究團隊使用二維材料進行許多研發與應用，二維材料有許多的優點，當材料的層數降至單層的情況下會發揮出許多半導體跟光電的特性，譬如二硫化鉬當從塊狀過渡到單層的時候，間接能隙會轉變成直接能隙、光吸收效率也會大幅提高，對於用來當作光偵測器和氣體感測器都可以得到不錯的效果，但是單純平面的感測器去和氣體接觸還是會有其極限，因此我們提出一個新的方法把二硫化鉬長成在結構化的藍寶石基板上，藉由完成三維結構並在不破壞二硫化鉬雙層的情況下提升偵測器的響應和測量極限。 在本實驗中，我們先使用化學氣象沉積法在圖像週期性排列的的藍寶石基板上長成雙層二硫化鉬，雙層的目的是為了避免晶體上的二硫化鉬會因為長成降溫的過程中發生斷裂的情形。在經過製程步驟完成元件後，我們將樣本放入儀器中藉由照光產生自由電子電洞對並通入一氧化氮氣體時，我們發現電流會有降低變化的趨勢，原因是氣體分子會和表面流動的載子形成鍵結。藉由電流和電阻訊號變化的特性可以讓我們當作偵測器使用，本實驗中我們使用單純平坦以及有結構的藍寶石基板，並發現有結構的基板會因和光的交互作用得到增益而比平坦的元件優良許多，因此我們相信在未來結構化基板所製造的氣體偵測器可以更加得到重視。

Recently, transition metal dichalcogenides had gained a lot of attention for their many advantages. For example, the layer numbers dominated the energy band gap from indirect to direct. Under monolayer condition, electronic and optical properties would emerge obviously, which was suitable for photodetector and gas sensor. In this work, we presented a new method to grow molybdenum disulfide onto the flat and three-dimensional structure to fabricate highly sensitivity gas sensor. To uniformly sulfurization the MoO3 to MoS2, bilayer was the optimized parameter to use. After the fabrication of gas sensor, we injected low part per million-concentration nitric oxide to the gas measurement chamber to react under the ultraviolet light illumination. Because of the type of MoS2 was n-type, the electrons were the major carriers produced by the ultraviolet light; the nitric oxide was the oxidizing type. Thus, when the gas interacted with the surface of MoS2, the current would decrease and the resistance would increase drastically. This phenomenon let us to analyze the signal change to make the better performance sensor. On the other hand, the three-dimensional structure could spread the light uniformly on the surface to produce more carriers to react. This result made us to believe that three-dimensional structure was the better choice for gas sensor to fabricate.