Park Changwon, Yoon Mina
School of Computational Sciences, Korea Institute for Advanced Study, Hoegiro 85, Seoul, 02455, Republic of Korea.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Sci Rep. 2022 May 5;12(1):7321. doi: 10.1038/s41598-022-10870-0.
Scanning tunneling microscopy (STM) is one of the indispensable tools to characterize surface structures, but the distinction between atomic geometry and electronic effects based on the measured tunneling current is not always straightforward. In particular, for single-atomic-thick materials (graphene or boron nitride) on metallic substrates, counterintuitive phenomena such as a larger tunneling current for insulators than for metal and a topography opposite to the atomic geometry are reported. Using first-principles density functional theory calculations combined with analytical modeling, we reveal the critical role of penetrating states of metallic substrates that surpass 2D material states, hindering the measurement of intrinsic 2D materials states and leading to topography inversion. Our finding should be instrumental in the interpretation of STM topographies of atomic-thick materials and in the development of 2D material for (opto)electronic and various quantum applications.
扫描隧道显微镜（STM）是表征表面结构不可或缺的工具之一，但基于测量的隧道电流区分原子几何结构和电子效应并非总是直截了当的。特别是，对于金属衬底上的单原子厚材料（石墨烯或氮化硼），有报道称存在一些违反直觉的现象，如绝缘体的隧道电流比金属的更大，以及形貌与原子几何结构相反。通过结合第一性原理密度泛函理论计算和解析模型，我们揭示了金属衬底穿透态的关键作用，这些穿透态超越了二维材料态，阻碍了对本征二维材料态的测量，并导致形貌反转。我们的发现将有助于解释原子厚材料的STM形貌，并有助于开发用于（光）电子和各种量子应用的二维材料。
