Correlation between morphology and local mechanical and electrical properties of van der Waals heterostructures

Borislav Vasić; Uroš Ralević; Sonja Aškrabić; Davor Čapeta; Marko Kralj

doi:10.1088/1361-6528/ac475a

Correlation between morphology and local mechanical and electrical properties of van der Waals heterostructures

Nanotechnology. 2022 Jan 21;33(15). doi: 10.1088/1361-6528/ac475a.

Authors

Borislav Vasić¹, Uroš Ralević¹, Sonja Aškrabić¹, Davor Čapeta², Marko Kralj²

Affiliations

¹ Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia.
² Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Bijenička 46, 10000, Zagreb, Croatia.

PMID: 34972096
DOI: 10.1088/1361-6528/ac475a

Abstract

Properties of van der Waals (vdW) heterostructures strongly depend on the quality of the interface between two dimensional (2D) layers. Instead of having atomically flat, clean, and chemically inert interfaces without dangling bonds, top-down vdW heterostructures are associated with bubbles and intercalated layers (ILs) which trap contaminations appeared during fabrication process. We investigate their influence on local electrical and mechanical properties of MoS₂/WS₂heterostructures using atomic force microscopy (AFM) based methods. It is demonstrated that domains containing bubbles and ILs are locally softer, with increased friction and energy dissipation. Since they prevent sharp interfaces and efficient charge transfer between 2D layers, electrical current and contact potential difference are strongly decreased. In order to reestablish a close contact between MoS₂and WS₂layers, vdW heterostructures were locally flattened by scanning with AFM tip in contact mode or just locally pressed with an increased normal load. Subsequent electrical measurements reveal that the contact potential difference between two layers strongly increases due to enabled charge transfer, while localI/Vcurves exhibit increased conductivity without undesired potential barriers.

Keywords: Kelvin probe force microscopy; atomic force microscopy; conductive atomic force microscopy; energy dissipation; nanofriction; two-dimensional materials; van der Waals heterostructures.