Band gap measurements of monolayer h-BN and insights into carbon-related point defects

Author(s):Show less -

Roman, Ricardo Javier Pena ^[1] ; Costa, Fabio J. R. Costa ^[1] ; Zobelli, Alberto ^[2] ; Elias, Christine ^[3] ; Valvin, Pierre ^[3] ; Cassabois, Guillaume ^[3] ; Gil, Bernard ^[3] ; Summerfield, Alex ^[4] ; Cheng, Tin S. ^[4] ; Mellor, Christopher J. ^[4] ; Beton, Peter H. ^[4] ; Novikov, V, Sergei ; Zagonel, Luiz F. ^[1]

Affiliation

^[1] Univ Estadual Campinas, UNICAMP, Gleb Wataghin Inst Phys, BR-13083859 Campinas - Brazil

^[2] Univ Paris Saclay, CNRS, Lab Phys Solides, F-91405 Orsay - France

^[3] Univ Montpellier, CNRS, Lab Charles Coulomb, UMR5221, F-34095 Montpellier - France

^[4] V, Univ Nottingham, Sch Phys & Astron, Nottingham NG7 2RD - England

• Document type: Journal article
• Source: 2D MATERIALS; v. 8, n. 4 OCT 2021.
• Web of Science Citations: 0

Abstract

Being a flexible wide band gap semiconductor, hexagonal boron nitride (h-BN) has great potential for technological applications like efficient deep ultraviolet light sources, building block for two-dimensional heterostructures and room temperature single photon emitters in the ultraviolet and visible spectral range. To enable such applications, it is mandatory to reach a better understanding of the electronic and optical properties of h-BN and the impact of various structural defects. Despite the large efforts in the last years, aspects such as the electronic band gap value, the exciton binding energy and the effect of point defects remained elusive, particularly when considering a single monolayer. Here, we directly measured the density of states of a single monolayer of h-BN epitaxially grown on highly oriented pyrolytic graphite, by performing low temperature scanning tunneling microscopy (STM) and spectroscopy (STS). The observed h-BN electronic band gap on defect-free regions is (6.8 +/- 0.2) eV. Using optical spectroscopy to obtain the h-BN optical band gap, the exciton binding energy is determined as being of (0.7 +/- 0.2) eV. In addition, the locally excited cathodoluminescence and photoluminescence show complex spectra that are typically associated to intragap states related to carbon defects. Moreover, in some regions of the monolayer h-BN we identify, using STM, point defects which have intragap electronic levels around 2.0 eV below the Fermi level. (AU)

• FAPESP's process: 18/08543-7 - Light emission by individual defects in 2D materials
• Grantee: Ricardo Javier Peña Román
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/23399-9 - Heterostructures in semiconducting nanowires: nanometric light emitters studied by scanning tunnelling microscopy
• Grantee: Luiz Fernando Zagonel
• Support Opportunities: Research Grants - Young Investigators Grants