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Small energy gap revealed in CrBr3 by scanning tunneling spectroscopy

Journal Article · · Physical Chemistry Chemical Physics. PCCP
DOI:https://doi.org/10.1039/d0cp05633b· OSTI ID:1780941
 [1];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [2]
  1. Univ. of Wyoming, Laramie, WY (United States). Department of Physics & Astronomy; University of Wyoming
  2. Univ. of Wyoming, Laramie, WY (United States). Department of Physics & Astronomy
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CrBr3 is a layered van der Waals material with magnetic ordering down to the 2D limit. For decades, based on optical measurements, it is believed that the energy gap of CrBr3 is in the range of 1.68–2.1 eV. However, controversial results have indicated that the band gap of CrBr3 is possibly smaller than that. An unambiguous determination of the energy gap is critical to the correct interpretations of the experimental results of CrBr3. Here, we present the scanning tunneling microscopy and spectroscopy (STM/S) results of CrBr3 thin and thick flakes exfoliated onto highly ordered pyrolytic graphite (HOPG) surfaces and density functional theory (DFT) calculations to reveal the small energy gap (peak-to-peak energy gap to be 0.57 ± 0.04 eV; or the onset signal energy gap to be 0.29 ± 0.05 eV from dI/dV spectra). Atomic resolution topography images show the defect-free crystal structure and the dI/dV spectra exhibit multiple peak features measured at 77 K. The conduction band – valence band peak pairs in the multi-peak dI/dV spectrum agree very well with all reported optical transitions. STM topography images of mono- and bi-layer CrBr3 flakes exhibit edge degradation due to short air exposure (~15 min) during sample transfer. The unambiguously determined small energy gap settles the controversy and is the key in better understanding CrBr3 and similar materials.

Research Organization:
Univ. of Wyoming, Laramie, WY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; Established Program to Stimulate Competitive Research (EPSCoR)
Grant/Contract Number:
SC0020074
OSTI ID:
1780941
Alternate ID(s):
OSTI ID: 2325240
OSTI ID: 2329318
Journal Information:
Physical Chemistry Chemical Physics. PCCP, Journal Name: Physical Chemistry Chemical Physics. PCCP Journal Issue: 5 Vol. 23; ISSN 1463-9076
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English

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