掃描穿隧電子顯微術於鉻摻雜α相碲化鍺之臨場裂解 (111) 面之研究

STM investigations of in-situ Cleaved Cr-Doped α-GeTe (111) Surfaces

虞甲斌(Jia-Bin Yu)

指導教授 ： 林敏聰

國立臺灣大學/理學院/物理學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702075

摘要

α相碲化鍺由於其特殊的菱形晶格結構，而展現出來鐵電性，即在電場下可以激發自發的電子極化效應。在塊材和表面α相碲化鍺中，Rashba效應也因材料內部電場的極化和在費米能階特殊的能帶結構，先後被預測和證實。這種可轉換的Rashba特性也為電場可調控自旋特性和其它自旋電子學的應用開闢了一條新的道路。
最新研究表明，通過錳摻雜，α相碲化鍺也能同時存在鐵磁性，拓寬了該材料研究的新可能。大量對α相碲化鍺在宏觀和介觀尺度的研究已經發表，然而對其在(111)面表面原子尺度的研究目前還是寥寥無幾。
在本篇論文中，利用臨場裂解技術(in-situ Cleavage)，我們得到了5%鉻摻雜的α相碲化鍺塊材乾淨的(111)表面。藉由掃描式穿隧電子顯微術(Scanning Tunneling Microscopy, STM)和其能譜(Scanning Tunneling Spectroscopy, STS)，結合α相碲化鍺的晶格特性，我們在原子尺度對其表面形貌和不同種類的晶體缺陷做出了相應的分析。並也研究了鍺表面和碲表面不同的電性結構。

關鍵字

α相碲化鍺 ； 臨場裂解 ； 掃描式穿隧電子顯微鏡 ； 掃描式穿隧電子能譜 ； 鐵電性 ； Rashba 效應

並列摘要

α-GeTe with a rhombohedral lattice possesses ferroelectricity, in which a spontaneous electric polarization can be operated using an external electric field. It has been predicted and manifested that bulk and surface Rashba states exist in α-GeTe based on internal electric polarization and band structures near the Fermi level. Such switchable Rashba properties bring a new path to electrical control of the non-volatile spin characters and versatile spintronic applications. Recently, coexistence of ferromagnetism was observed as well by doping Mn into α-GeTe, which further expands the usage of this emergent crystal. While studies at the macro- and mesoscale have been carried out, no investigations at the atomic scale on α-GeTe (111) surface has been reported yet. In this work, in-situ cleaved clean (111) surfaces of bulk 5%-Cr-doped GeTe is resolved by scanning tunneling microscopy and spectroscopy. In combination with the lattice model, investigations of the surface terminations and different types of defects are conducted within atomic resolution. Electronic structures of domain-like regions with Ge- and Te-terminations are studied as well.

並列關鍵字

Cr-doped α-GeTe ； in-situ cleavage ； scanning tunneling microscopy ； scanning tunneling spectroscopy ； Ferroelectric ； Rashba spin splitting

參考文獻

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