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Title: Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy

Abstract

Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 and 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.

Authors:
; ;  [1]
  1. New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)
Publication Date:
OSTI Identifier:
22596910
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 119; Journal Issue: 11; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION SPECTROSCOPY; BRILLOUIN ZONES; DENSITY OF STATES; ELECTRONS; ENERGY LOSSES; ENERGY-LOSS SPECTROSCOPY; LAYERS; MOLYBDENUM SULFIDES; NANOSTRUCTURES; PHOTOLUMINESCENCE; RESOLUTION; RHENIUM SULFIDES; SILICON OXIDES; TWO-DIMENSIONAL CALCULATIONS; VAN DER WAALS FORCES; ZINC OXIDES

Citation Formats

Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sahu, R., Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sarkar, Sumanta, and Peter, Sebastian C. Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy. United States: N. p., 2016. Web. doi:10.1063/1.4944431.
Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sahu, R., Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sarkar, Sumanta, & Peter, Sebastian C. Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy. United States. doi:10.1063/1.4944431.
Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sahu, R., Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in, Sarkar, Sumanta, and Peter, Sebastian C. Mon . "Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy". United States. doi:10.1063/1.4944431.
@article{osti_22596910,
title = {Layer specific optical band gap measurement at nanoscale in MoS{sub 2} and ReS{sub 2} van der Waals compounds by high resolution electron energy loss spectroscopy},
author = {Dileep, K., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in and Sahu, R. and Datta, R., E-mail: dileep@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in and Sarkar, Sumanta and Peter, Sebastian C.},
abstractNote = {Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 and 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.},
doi = {10.1063/1.4944431},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 11,
volume = 119,
place = {United States},
year = {2016},
month = {3}
}