二維三碘化鉻的原子級電子結構分析

Abstract

單層三碘化鉻(CrI3)是目前發現最薄的鐵磁材料，具有較低的居里溫度~45 K，近期在自旋電子器件應用上受到了極大的關注。到目前為止，大多數研究都集中在三碘化鉻的磁性和晶體結構上。然而，實驗上至今仍缺少實空間費米能階附近的基本電子結構相關研究。 在本研究中，我們利用掃描穿隧顯微鏡(STM)及掃描穿隧能譜(STS)來研究室溫下三碘化鉻的原子表面結構和狀態能階密度。結構上的研究成果，驗證三碘化鉻於室溫的條件之下，晶體結構為單斜晶系(C2/m)排列，和之前結構研究相符。電性上的研究成果，主要有二個發現: (一) 三碘化鉻的狀態能階密度的量測，以及穿隧電流結果顯示，導電帶的電子結構於穿隧電流之貢獻，主要來自於表面鉻原子；(二) 三碘化鉻的碘缺陷導致能帶間隙縮小的行為。

Monolayer Chromium Triiodide (CrI3), being the thinnest ferromagnetic material, has recently received significant attention because of a low Curie temperature ~ 45 K. Until now, most studies focus on the magnetic properties and crystal structure of CrI3. ¬However, the real-space image and the fundamental electronic structure is still missing. Here, we utilize scanning tunneling microscopy and spectroscopy (STM/S) to investigate both the direct atomic surface structure and the density of states of CrI3 at room temperature. Results show that the crystal structure is monoclinic (C2/m), consistent with the previous studies. Moreover, the electronic properties of CrI3 have two main features. We measure the band gap of CrI3 and observe that the tunneling currents in the conduction band, which are determined from Chromium atoms, act more obviously than they do in the valance band. The other, the defects of CrI3 result in the band gap narrowing.