透過氨化前處理基板修復二氧化鉬之硫空缺

Abstract

二維過渡金屬二硫屬化物（2D TMDCs）由於其獨特的電學和光學性質，在光電領域引起了相當大的關注。然而，在合成過程中產生的原子級缺陷限制了它們的真正潛力。雖然目前學界較常見的後處理技術可以一定程度地減輕這些缺陷，但這些技術不僅引入了複雜性，同時也對過渡金屬硫氧化物的品質產生了不利影響。在這項研究中，我們提出了一種簡單且有效的替代方案，利用生長用基板之預處理作為解決二氧化鉬中原子缺陷所帶來的問題。透過在生長前對藍寶石基板進行低溫氨化處理，光譜表徵與原子級顯微鏡證實了藍寶石表面的氮能鈍化二氧化鉬晶格內的硫空缺；同時，第一原理計算結果以及光、電性量測說明了被氮原子填補的硫空缺可消除能隙中之缺陷態密度，並呈現了P型參雜的行為。不僅如此，於金屬異質接面的載子傳輸性質也得到改善，修復缺陷後的二氧化鉬使其接觸電阻下降了三倍並大幅地提升光偵測器性能達到十倍以上。這些發現為未來高性能二維電子器件的開發開辟了令人興奮的可能性。

2D transition metal dichalcogenides (2D TMDCs) have garnered considerable attention in the field of optoelectronics due to their unique electric and optical properties. However, the presence of atomic vacancies during the synthesis process has imposed limitations on their potential. Although post-treatment techniques have been employed to mitigate these vacancies, they introduce complexities and adversely impact the quality of TMDCs. In this study, we propose an alternative approach that leverages pretreatment as a simple yet effective solution to address the vacancy issue in MoS2. By conducting a low-temperature nitridation of the sapphire substrate prior to growth, we demonstrate a non-destructive method for modifying MoS2 without introducing additional processing steps or raising the thermal budget. Through spectroscopic characterization and atomic-resolution microscopy, we unveil the incorporation of nitrogen from the surface layer of the pre-treated sapphire into chalcogen vacancies within the MoS2 lattice. The resulting nitrogen-saturated MoS2 exhibits a reduction in mid-gap states and demonstrates a p-type doping behavior, which is confirmed through ab-initio calculations and optoelectronic measurements. The effectiveness of the pretreatment approach is evidenced by a threefold decrease in contact resistance and a tenfold improvement in the performance of 2D photodetectors. These findings open up exciting possibilities for the development of high-performance 2D electronics in the future.