Barja Sara, Refaely-Abramson Sivan, Schuler Bruno, Qiu Diana Y, Pulkin Artem, Wickenburg Sebastian, Ryu Hyejin, Ugeda Miguel M, Kastl Christoph, Chen Christopher, Hwang Choongyu, Schwartzberg Adam, Aloni Shaul, Mo Sung-Kwan, Frank Ogletree D, Crommie Michael F, Yazyev Oleg V, Louie Steven G, Neaton Jeffrey B, Weber-Bargioni Alexander
Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Departamento de Física de Materiales, Centro de Física de Materiales, University of the Basque Country UPV/EHU-CSIC, Donostia-San Sebastián, 20018, Spain.
Nat Commun. 2019 Jul 29;10(1):3382. doi: 10.1038/s41467-019-11342-2.
Chalcogen vacancies are generally considered to be the most common point defects in transition metal dichalcogenide (TMD) semiconductors because of their low formation energy in vacuum and their frequent observation in transmission electron microscopy studies. Consequently, unexpected optical, transport, and catalytic properties in 2D-TMDs have been attributed to in-gap states associated with chalcogen vacancies, even in the absence of direct experimental evidence. Here, we combine low-temperature non-contact atomic force microscopy, scanning tunneling microscopy and spectroscopy, and state-of-the-art ab initio density functional theory and GW calculations to determine both the atomic structure and electronic properties of an abundant chalcogen-site point defect common to MoSe and WS monolayers grown by molecular beam epitaxy and chemical vapor deposition, respectively. Surprisingly, we observe no in-gap states. Our results strongly suggest that the common chalcogen defects in the described 2D-TMD semiconductors, measured in vacuum environment after gentle annealing, are oxygen substitutional defects, rather than vacancies.
硫族元素空位通常被认为是过渡金属二硫属化物（TMD）半导体中最常见的点缺陷，这是因为它们在真空中的形成能较低，并且在透射电子显微镜研究中经常被观察到。因此，二维TMD中意外的光学、输运和催化性质被归因于与硫族元素空位相关的带隙态，即使在没有直接实验证据的情况下也是如此。在这里，我们结合低温非接触原子力显微镜、扫描隧道显微镜和光谱学，以及最先进的从头算密度泛函理论和GW计算，来确定分别通过分子束外延和化学气相沉积生长的MoSe和WS单层中常见的丰富硫族元素位点的点缺陷的原子结构和电子性质。令人惊讶的是，我们没有观察到带隙态。我们的结果强烈表明，在温和退火后在真空环境中测量的所述二维TMD半导体中常见的硫族元素缺陷是氧替代缺陷，而不是空位。
