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

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 $(6.8\pm 0.2)$ eV. Using optical spectroscopy to obtain the h-BN optical band gap, the exciton binding energy is determined as being of $(0.7\pm 0.2)$ 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.

50 Pages, 8 Figures, 100+ references

References in corpus (15)

• 2D materials and van der Waals heterostructures
• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Determination of band alignment in the single layer MoS2/WSe2 heterojunction
• First direct observation of Dirac fermions in graphite
• Defect-related photoluminescence of hexagonal boron nitride
• Coupling of excitons and defect states in boron-nitride nanostructures
• How Substitutional Point Defects in Two-Dimensional WS${}_2$ Induce Charge Localization, Spin-Orbit Splitting, and Strain
• Band gap measurements of monolayer h-BN and insights into carbon-related point defects
• Band gap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures
• Reversible hydrogenation and band gap opening of graphene and graphite surfaces probed by scanning tunneling spectroscopy
• Contact-Induced Semiconductor-to-Metal Transition in Single-Layer WS${}_2$
• Diffusion quantum Monte Carlo and GW study of the electronic properties of monolayer and bulk hexagonal boron nitride
• Tunneling-current-induced local excitonic luminescence in p-doped WSe${}_2$ monolayers
• Luminescent defects in a few-layer h-BN film grown by molecular beam epitaxy
• Morphology, ordering, stability, and electronic structure of carbon-doped hexagonal boron nitride

Cited by in corpus (4)

• Band gap measurements of monolayer h-BN and insights into carbon-related point defects
• Polarons in two-dimensional atomic crystals
• Theoretical methods for excitonic physics in two-dimensional materials
• Design and implementation of a device based on an off-axis parabolic mirror to perform luminescence experiments in a scanning tunneling microscope