How high is a MoSe2monolayer?

Abstract

Transition metal dichalcogenides (TMDCs) have attracted significant attention for optoelectronic, photovoltaic and photoelectrochemical applications. The properties of TMDCs are highly dependent on the number of stacked atomic layers, which is usually counted post-fabrication, using a combination of optical methods and atomic force microscopy height measurements. Here, we use photoluminescence spectroscopy, Raman spectroscopy, and three different AFM methods to demonstrate significant discrepancies in height measurements of exfoliated MoSe₂flakes on SiO₂depending on the method used. We also highlight the often overlooked effect that electrostatic forces can be misleading when measuring the height of a MoSe₂flake using AFM.

Keywords: 2D materials; Raman spectroscopy; Transition metal dichalcogenides (TMDCs); atomic force microscopy (AFM); kelvin probe force microscopy (KPFM); molybdenum diselenide (MoSe2); photoluminescence spectroscopy (PL).