Defects and Surface Structural Stability of MoTe2 Under Vacuum Annealing.
Defects and Surface Structural Stability of MoTe2 Under Vacuum Annealing.
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真空退火条件下MoTe2的缺陷及表面结构稳定性
DOI：
10.1021/acsnano.7b04984
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发表时间：
2017-11
期刊：
影响因子：
17.1
通讯作者：
Hui Zhu;Qingxiao Wang;Lanxia Cheng;R. Addou;Jiyoung Kim;Moon J. Kim;R. Wallace
中科院分区：
文献类型：
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作者：
Hui Zhu;Qingxiao Wang;Lanxia Cheng;R. Addou;Jiyoung Kim;Moon J. Kim;R. Wallace
了解过渡金属二卤化物的结构稳定性对于避免表面/界面退化是必要的。本工作用扫描隧道显微镜和扫描电子显微镜研究了2H-MoTe2在500℃以下热处理后的结构稳定性。在室温下剥离的样品表面，观察到了由过剩的Te原子产生的原子次表面施主，并呈现为纳米尺寸的电子诱导突起，叠加了MoTe2的六方晶格结构。在200℃以下的热处理条件下，表面分解引起的团簇缺陷和Te空位很容易被检测到，并且随着温度的升高，缺陷和空位的程度增加。在Te空位和热能的驱动下，400℃退火15min后，形成了强烈的60°反转晶界，形成了“马轮”状的形貌。扫描隧道光谱确定了位于磁区边界和磁区中心的电子态。为了防止在较高温度下大量的Te损失，在较高的温度下，Mo6Te6纳米线的形成和大量的解吸诱导的刻蚀效应将同时发生，测试了MoTe2上单层石墨烯覆盖的表面和边缘钝化。通过这种钝化策略，MoTe2的结构稳定性大大提高，最高可达500℃，没有明显的结构缺陷。
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.