硫缺陷於單層二硫化鉬(MoS2)之磁-電性質調控與研究

Abstract

於此研究，藉由Ar與O2之熱處理，成功控制並佈植硫空缺(sulfur vacancy, Vs)於單層二硫化鉬(MoS2)主結構與邊角上。在氬氣(Ar)熱處理過程中，硫原子會因為熱處理應力釋放的效應，使部分結構從2H-MoS2(低自旋態)轉變為1T-MoS2(高自旋態)，Vs佈植於單層二硫化鉬主結構上，而增加其磁性質，且單層MoS2場效電晶體之載子遷移率提升36%，使磁-電耦合之效應更明顯。然而在經過氧氣(O2)熱處理後，從磁力顯微鏡(MFM)的影像可以得知，硫原子脫附會傾向於集中在單層MoS2的邊角區域，且飽和磁化量較處理前微弱的鐵磁性有更顯著的提升。利用第一原理計算模擬不同比例硫空缺於單層MoS2邊角區域，證實當邊角上的硫空缺增加時，會使自旋極化率越趨明顯，這表示單層MoS2在邊角區域的磁性相當敏感，有機會進一步將邊角與磁電耦合效應結合。本研究強調硫空缺對於單層MoS2之磁電特性相當敏感，且與2H/1T之結構相和邊角有相當大的關聯性，也期許能為單層MoS2應用於自旋電子元件開啟新的契機。

In this study we demonstrate a successful control of single-layer MoS2’s magneto-electrical properties by the creation of sulfur vacancy (VS) with different gas treatments. With an Ar treatment, a full-sheet sulfur depletion of MoS2 was enabled, which resulted in a structurally-relaxed 2H (low-spin)→1T (high-spin) phase transition accompanied by a significant magnetic enhancement. This also led to an increase of carrier mobility by 36% in a MoS2 field-effect-transistor. This indicates that the Ar implementation could effectively drive the MoS2’s magneto-electrical response. An O2 treatment, however, tended to desorb sulfur at the MoS2’s edge with a local spin-polarization enhancement as probed by magnetic force microscopy, which was coupled to different FET modulations. Using first-principle calculation we theoretically terminated the MoS2’s edge with VS gradient, where band-splitting appeared more prominent with increasing VS specifically at the edge. This tunable band-gap characteristic suggests edge-sensitive magneto-electrical nature of the single-layer MoS2 from a different approach. Our work highlights the strong sensitivity of MoS2’s magneto-electrical properties to the nature of VS, by correlating its effects with the edge and 2H/1T phase behaviors. This is expected to open opportunities for tailoring this material for spintronic applications.