Phase transition from Au-Te surface alloy towards tellurene-like monolayer
Phase transition from Au-Te surface alloy towards tellurene-like monolayer
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DOI：
10.1088/2053-1583/abc7f9
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发表时间：
2021-01-01
期刊：
影响因子：
5.5
通讯作者：
Bendounan, Azzedine
中科院分区：
文献类型：
--
作者：
Bouaziz, Meryem;Zhang, Wei;Bendounan, Azzedine
二维（2D）硫族化合物基层已被证明是下一代具有潜在高科技应用的材料，在纳米尺度上控制其性能非常重要。本文讨论了Au（111）表面在真空中高温气相沉积碲（Te）后的结构和电子性质。需要形成2D AuTe 2金属二硫属化物或更确切地说Au-Te合金单层（ML）或甚至碲烯单层的情景值得解决。在这个目的中，低能电子衍射（LEED）支持的扫描隧道显微镜（STM）显示存在几个表面重建取决于Te膜厚度在亚单层制度。我们观察到Au（111）表面的自旋分裂Shockley态在Te沉积后仍然存在，甚至向更高的结合能移动，这表明在界面处存在电荷转移。对于0.33 ML的Te的覆盖率，新的色散带观察角分辨光电子能谱（ARPES），这是由Te和Au的电子状态之间的强杂交产生的。在约化表面布里渊区（R-SBZ）的边界处具有相当低的强度和回折，这些电子带代表了自然2D电子气存在的证据，其强烈地受到表面重构的干扰。因此，有可能在表面处形成Au-Te合金。通过增加覆盖率到0.5 ML，丰富的，厚度依赖性的过渡开发从表面合金碲样结构，并完全排除AuTe 2单层的生长。表面合金和碲烯单层具有半导体特性，其占据态的间隙约为0.65 eV。
Two-dimensional (2D) chalcogen-based layers have proven to be the next generation of materials for potential high-tech applications, and it is very important to control their properties at the nanoscale. Herein, we discuss the structural and electronic properties of Au(111) surface after being exposed to high temperature vapor deposition of Tellurium (Te) in ultrahigh vacuum. The scenarios entailing the formation of 2D AuTe2 metal dichalcogenide or rather Au-Te alloy monolayer (ML) or even Tellurene single layer deserved to be addressed. In this purpose, low energy electron diffraction (LEED) supported by scanning tunneling microscopy (STM) shows the existence of several surface reconstructions depending on the Te film thickness in the sub-monolayer regime. We observed that the well-known spin-split Shockley state of the Au(111) surface survives the Te deposition and is even shifted to higher binding energy, suggesting a charge transfer at the interface. For a coverage of 0.33 ML of Te, new dispersive bands are observed by angle-resolved photoemission (ARPES), which arise from a strong hybridization between the electronic states of Te and Au. With a substantially low intensity and a back-folding at the boundaries of the reduced surface Brillouin zone (R-SBZ), these electronic bands represent a proof of the existence of a naturel 2D electron gas, strongly disturbed by the surface reconstruction. It is therefore possible that an Au-Te alloy is formed at the surface. By increasing the coverage to 0.5 ML, a rich, thickness-dependent transition develops from the surface alloy to Tellurene-like structure and completely excludes the growth of AuTe2 monolayer. Both the surface alloy and the Tellurene monolayer have a semiconductor character with a gap in the occupied states of about 0.65 eV.