Electronic Density of States of CrBr₃ studied by Scanning Tunneling Microscopy and Spectroscopy (STM/S)

CrBr₃ is a van der Waals material exhibiting magnetism at the 2D limit. Despite the great attention on magnetic properties, the electronic properties of CrBr₃ are relatively unexplored. Here, the study of thin flakes of CrBr₃ exfoliated on Highly Ordered Pyrolytic Graphite (HOPG) surface was performed using STM/S. The atomic resolution topography, multi-peak dI/dV measurements on the bulk CrBr₃ as well as at the monolayer limit will be presented and discussed. Topography agrees with the crystal structures while the multi-peak dI/dV spectra agree extremely well with reported optical measurements. However, the observed energy gap extracted from the dI/dV measurements is determined to be ~0.57 eV, much smaller than the previously believed ~1.7 eV observed by absorption spectrum. DFT calculated DOS failed to reproduce two peaks near the Fermi energy. Further studies are needed to explain the discrepancy. The mono- and bi-layer flakes depict degradation at the edges due to air exposure during sample transfer. These observations provide important information towards the fundamental understanding of CrBr₃.