Tunneling-current-induced local excitonic luminescence in p-doped WSe<sub>2</sub>monolayers

Román, Ricardo Javier Peña; Auad, Yves; Grasso, Lucas; Alvarez, F.; Barcelos, Ingrid D.; Zagonel, Luiz Fernando

doi:10.1039/d0nr03400b

Cited by 24 publications

(31 citation statements)

References 77 publications

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“…This setup has also been previously used to investigate WSe 2 and MoS 2 monolayers. 56,57 Electronic band gap, optical band gap and exciton binding energy Since monolayer h-BN is an atomically thin and a wide band gap material, access to its electronic structure is always a highly challenging experimental and theoretical task. Within the last twenty years, the h-BN electronic band gap has been calculated a number of times within the GW approximation, while the optical response has been calculated using the Bethe-Salpeter equation.…”

Section: Sample and Methods Descriptionsmentioning

confidence: 99%

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

Román¹,

Costa²,

Zobelli³

et al. 2021

2D Mater.

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Being a flexible wide band gap semiconductor, hexagonal boron nitride (h-BN) has great potential for technological applications like efficient deep ultraviolet (DUV) light sources, building block for two-dimensional heterostructures and room temperature single photon emitters in the UV 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 (LT-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.

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Section: Sample and Methods Descriptionsmentioning

confidence: 99%

“…Furthermore, a direct correlation with the optical emission is missing. Even though STM is a tool able to identify atomic defects in 2D materials, 56,[93][94][95][96] STM/STS measurements of point defects in monolayer h-BN have not been reported yet.…”

Section: Electronic Structure and Light Emission Related To Point Def...mentioning

confidence: 99%

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

Román¹,

Costa²,

Zobelli³

et al. 2021

2D Mater.

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“…Moreover, TMDs offer unique opportunities for fundamental research on exciton physics in 2D materials. Recently, scanning tunneling microscopy (STM)-induced luminescence (STML) has emerged as a promising nanoscopic probe of the optoelectronic properties of monolayer TMDs [6][7][8][9][10][11]. There is experimental evidence that, under certain conditions, STML reveals the intrinsic excitonic species of the excited TMD monolayer [7].…”

Section: Introductionmentioning

confidence: 99%

Electroluminescence of monolayer WS2 in a scanning tunneling microscope: Effect of bias polarity on spectral and angular distribution of emitted light

Román

Pommier²,

Bretel³

et al. 2022

Phys. Rev. B

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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“…The height of 1L-MoS 2 is predicted to be ∼0.7 nm, while the experimental thickness by AFM is expected to be higher, due to the factors discussed above. For example, ref reported 1L-WSe 2 on Au with a thickness ∼2.4 nm, attributed to water molecules trapped between 1L-WSe 2 and Au, while ref reported ∼1.6 nm for 1L-MoS 2 on hBN, assigned to PDMS residues trapped between both materials. Our AFM data indicate a 1L-MoS 2 height ∼1.3 nm, lower than expected for PDMS contaminants .…”

Section: Methodsmentioning

confidence: 99%

Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS₂ and Gold

Yong

et al. 2020

ACS Nano

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Electron transport across the transition metal dichalcogenide (TMD)-metal interface plays an important role in determining the performance of TMD-based optoelectronic devices. However, the robustness of this process against structural heterogeneities remains unexplored, to the best of our knowledge. Here, we employ a combination of time-resolved photoemission electron microscopy (TR-PEEM) and atomic force microscopy to investigate the spatially resolved hotelectron transfer dynamics at the monolayer (1L) MoS2/Au interface. A spatially heterogeneous distribution of 1L-MoS2/Au gap distances, along with the sub-80-nm spatial-and sub-60-fs temporal resolution of TR-PEEM, permits the simultaneous measurement of electron transfer rates across a range of 1L-MoS2/Au distances. These decay exponentially as a function of distance, with an attenuation coefficient 𝛽 ~ 0.06 ± 0.01 Å -1 , comparable to molecular wires.Ab Initio simulations suggest that surface plasmon-like states mediate hot-electron transfer, hence accounting for its weak distance dependence. The weak distance dependence of the interfacial hot-electron transfer rate indicates that this process is insensitive to distance fluctuations at TMD-metal interfaces, thus motivating the further exploration of optoelectronic devices based on hot carriers.

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Tunneling-current-induced local excitonic luminescence in p-doped WSe₂monolayers

Abstract:
Probing and controlling excitonic species in a 2D-semiconductor on a metallic support using tunneling electrons as a nanoscale excitation source.

Cited by 24 publications

References 77 publications

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

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

Electroluminescence of monolayer WS2 in a scanning tunneling microscope: Effect of bias polarity on spectral and angular distribution of emitted light

Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS₂ and Gold

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Tunneling-current-induced local excitonic luminescence in p-doped WSe2monolayers

Abstract: Probing and controlling excitonic species in a 2D-semiconductor on a metallic support using tunneling electrons as a nanoscale excitation source.

Cited by 24 publications

References 77 publications

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

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

Electroluminescence of monolayer WS2 in a scanning tunneling microscope: Effect of bias polarity on spectral and angular distribution of emitted light

Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS2 and Gold

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Product

Resources

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Tunneling-current-induced local excitonic luminescence in p-doped WSe₂monolayers

Abstract:
Probing and controlling excitonic species in a 2D-semiconductor on a metallic support using tunneling electrons as a nanoscale excitation source.

Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS₂ and Gold