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Title: Optical properties of large-area ultrathin MoS{sub 2} films: Evolution from a single layer to multilayers

We investigated the optical properties of ultrathin MoS{sub 2} films (number of layers: N = 1, 2, 4, and 12) using Raman spectroscopy, photoluminescence (PL) spectroscopy, and spectroscopic ellipsometry. We estimated the layer thicknesses based on Raman spectra. We characterized the microstructural properties of a single-layer MoS{sub 2} film using atomic force microscopy. We measured the lowest-energy A and B excitons using PL spectroscopy. We measured the ellipsometric angles (Ψ and Δ) of MoS{sub 2} thin films using spectroscopic ellipsometry, and obtained the dielectric functions as the films' thickness changed from a single layer to multi-layers. We determined the films' optical gap energies from the absorption coefficients. Applying the standard critical point model to the second derivative of the dielectric function (d{sup 2}ε(E)/dE{sup 2}), we determined several critical point energies. The d{sup 2}ε(E)/dE{sup 2} spectra showed doublet peaks around 3 eV corresponding to the C and D transitions, as well as doublet peaks around 2 eV corresponding to the A and B transitions. These doublet structures at 3 eV are attributed to the transitions in the Brillouin zone between the Γ and K points.
Authors:
; ; ; ;  [1] ; ;  [2] ;  [3]
  1. Department of Applied Physics, Kyung Hee University, Yong-In 446-701 (Korea, Republic of)
  2. School of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
  3. SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22402621
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 18; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ATOMIC FORCE MICROSCOPY; BRILLOUIN ZONES; DIELECTRIC MATERIALS; ELLIPSOMETRY; EV RANGE; LAYERS; MICROSTRUCTURE; MOLYBDENUM SULFIDES; OPTICAL PROPERTIES; PHOTOLUMINESCENCE; RAMAN SPECTRA; RAMAN SPECTROSCOPY; THICKNESS; THIN FILMS