Grewal Abhishek, Wang Yuqi, Münks Matthias, Kern Klaus, Ternes Markus
Max Planck Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich, Germany.
Beilstein J Nanotechnol. 2021 Jun 17;12:559-565. doi: 10.3762/bjnano.12.46. eCollection 2021.
Combined scanning tunnelling and atomic force microscopy using a qPlus sensor enables the measurement of electronic and mechanic properties of two-dimensional materials at the nanoscale. In this work, we study hexagonal boron nitride (-BN), an atomically thin 2D layer, that is van der Waals-coupled to a Cu(111) surface. The system is of interest as a decoupling layer for functional 2D heterostructures due to the preservation of the -BN bandgap and as a template for atomic and molecular adsorbates owing to its local electronic trapping potential due to the in-plane electric field. We obtain work function (Φ) variations on the -BN/Cu(111) superstructure of the order of 100 meV using two independent methods, namely the shift of field emission resonances and the contact potential difference measured by Kelvin probe force microscopy. Using 3D force profiles of the same area we determine the relative stiffness of the Moiré region allowing us to analyse both electronic and mechanical properties of the 2D layer simultaneously. We obtain a sheet stiffness of 9.4 ± 0.9 N·m, which is one order of magnitude higher than the one obtained for -BN/Rh(111). Using constant force maps we are able to derive height profiles of -BN/Cu(111) showing that the system has a corrugation of 0.6 ± 0.2 Å, which helps to demystify the discussion around the flatness of the -BN/Cu(111) substrate.
使用qPlus传感器的组合扫描隧道显微镜和原子力显微镜能够在纳米尺度上测量二维材料的电学和力学性质。在这项工作中，我们研究了六方氮化硼（h-BN），一种原子级薄的二维层，它通过范德华力耦合到Cu(111)表面。由于h-BN带隙的保留，该系统作为功能性二维异质结构的解耦层具有重要意义；同时，由于其面内电场导致的局部电子俘获势，它也可作为原子和分子吸附物的模板。我们使用两种独立的方法，即场发射共振的位移和开尔文探针力显微镜测量的接触电势差，获得了h-BN/Cu(111)超结构上约100 meV量级的功函数（Φ）变化。通过相同区域的三维力分布，我们确定了莫尔区域的相对刚度，从而能够同时分析二维层的电学和力学性质。我们得到的面内刚度为9.4±0.9 N·m，比h-BN/Rh(111)的刚度高一个数量级。使用恒力图，我们能够得出h-BN/Cu(111)的高度分布，表明该系统的起伏为0.6±0.2 Å，这有助于揭开围绕h-BN/Cu(111)衬底平整度的讨论之谜。
