二硒化錫的單層結構對於二氧化氮與氨氣的吸附性質的第一原理研究

Abstract

二硒化錫是一種非均向性的多層材料，具有豐富的物理性質，具有各種不同應用的可能性。本論文使用第一原理計算來研究二硒化錫的氣體偵測特性。理論模擬結果顯示電子從二硒化錫轉移到二氧化氮氣體分子上，其電子轉移的方向與氨氣相反。值得注意的是，二硒化錫吸附二氧化氮分子之後，在費米能量附近出現一條平坦的能帶，該能帶主要為二氧化氮分子所佔據。與氨氣相比，吸附在二硒化錫上的二氧化氮分子具有較低的吸附能和較高的電荷轉移量。與原始單層的二硒化錫相比，含有Se空缺的單層二硒化錫明顯增強了對二氧化氮吸附的敏感性。當吸附二氧化氮分子時，摻雜氧原子的單層二硒化錫與原始單層二硒化錫顯示出相似的靈敏度。但是，只有摻雜氮原子的單層二硒化錫顯示出對二氧化氮和氨氣吸附敏感度的明顯增強。雖然我們之前用聚苯乙烯微米顆粒裝飾石墨烯表面的相關研究，結果呈現前述系統可增強二氧化氮分子感測度。然而，前述系統會包含太多原子，我們無法確定是否可以直接用VASP來做計算。在未來的工作中，我們會再嘗試找尋適當的方式來計算前述複雜系統的氣體偵測性質。

SnSe2 is an anisotropic binary-layered material with rich physics, which is used for a variety of potential applications. Here, we investigate the gas-sensing properties of SnSe2 with first-principles calculations. Theoretical simulations indicate that electrons transfer from SnSe2 to NO2, whereas the direction of charge transfer is the opposite for NH3. Notably, a flat molecular band appears around the Fermi energy after NO2 adsorption and the induced molecular band is close to the conduction band minimum. Moreover, compared with NH3, NO2 molecules adsorbed on SnSe2 have lower adsorption energy and a higher charge transfer value. Compared with the gas molecular adsorbed on pristine SnSe2 monolayer, the Se-vacancy SnSe2 monolayer obviously enhances sensitivity to NO2 adsorption. The O-doped SnSe2 monolayer shows similar sensitivity to the pristine SnSe2 monolayer when adsorbing NO2 molecule. However, only the N-doped SnSe2 monolayer represents a visible enhancement for NO2 and NH3 adsorption. Our previous work shows NO2 sensing enhancement of graphene decorated with polystyrene beads, which include many atoms that we cannot be sure if it could be calculated by VASP. In future work, we will try to simulate this complex system.