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Defects and Surface Structural Stability of MoTe2 Under Vacuum Annealing
ACS Nano ( IF 17.1 ) Pub Date : 2017-11-14 00:00:00 , DOI: 10.1021/acsnano.7b04984
Hui Zhu 1 , Qingxiao Wang 1 , Lanxia Cheng 1 , Rafik Addou 1 , Jiyoung Kim 1 , Moon J. Kim 1 , Robert M. Wallace 1
Affiliation  

Understanding the structural stability of transition-metal dichalcogenides is necessary to avoid surface/interface degradation. In this work, the structural stability of 2H-MoTe2 with thermal treatments up to 500 °C is studied using scanning tunneling microscopy and scanning transmission electron microscopy. On the exfoliated sample surface at room temperature, atomic subsurface donors originating from excess Te atoms are observed and presented as nanometer-sized, electronically-induced protrusions superimposed with the hexagonal lattice structure of MoTe2. Under a thermal treatment as low as 200 °C, the surface decomposition-induced cluster defects and Te vacancies are readily detected and increase in extent with the increasing temperature. Driven by Te vacancies and thermal energy, intense 60° inversion domain boundaries form resulting in a “wagon wheel” morphology after 400 °C annealing for 15 min. Scanning tunneling spectroscopy identified the electronic states at the domain boundaries and the domain centers. To prevent extensive Te loss at higher temperatures, where Mo6Te6 nanowire formation and substantial desorption-induced etching effects will take place simultaneously, surface and edge passivation with a monolayer graphene coverage on MoTe2 is tested. With this passivation strategy, the structural stability of MoTe2 is greatly enhanced up to 500 °C without apparent structural defects.

中文翻译:

MoTe 2在真空退火下的缺陷和表面结构稳定性

为了避免表面/界面退化,必须了解过渡金属二卤化物的结构稳定性。在这项工作中,使用扫描隧道显微镜和扫描透射电子显微镜研究了在高达500°C的热处理条件下2H-MoTe 2的结构稳定性。在室温下,在剥落的样品表面上,观察到源自过量Te原子的原子表面下的施主,并以纳米级的电子诱导突起与MoTe 2的六方晶格结构叠加的形式呈现。在低至200°C的热处理下,容易检测出表面分解引起的团簇缺陷和Te空位,并随温度的升高而增加。在Te空位和热能的驱动下,剧烈的60°反转畴边界形成,在400°C退火15分钟后形成“车轮”形态。扫描隧道光谱法确定了在畴边界和畴中心处的电子状态。为了防止高温下大量Te的损失,同时发生Mo 6 Te 6纳米线的形成和大量解吸诱导的蚀刻效果,在MoTe 2上进行单层石墨烯覆盖的表面和边缘钝化经过测试。通过这种钝化策略,MoTe 2的结构稳定性在高达500°C的条件下得到了极大的增强,而没有明显的结构缺陷。
更新日期:2017-11-16
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