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Title: In Pursuit of 2D Materials for Maximum Optical Response

Abstract

Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron–photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance ($A$) and reflectance ($R$) in 2D materials and also conduct a computational survey to seek out those with best $A$ and $R$ in various frequency ranges, from mid-infrared to deep-ultraviolet. We find that 2D boron has broadband reflectance R > 99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe–Salpeter equation. We found several monolayer semiconductors with absorbances ≳30% in different optical ranges, which are more than half of the maximum possible value, Alim = 1/2, for a freestanding 2D material. Our study predicts 2D materials which can potentially be used in ultrathin reflectors and absorbers for optoelectronic application in various frequency ranges.

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1];  [1]
  1. Rice Univ., Houston, TX (United States). Dept. of Materials Science and NanoEngineering
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1543718
Resource Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 12; Journal Issue: 11; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Chemistry; Science & Technology - Other Topics; Materials Science

Citation Formats

Gupta, Sunny, Shirodkar, Sharmila N., Kutana, Alex, and Yakobson, Boris I. In Pursuit of 2D Materials for Maximum Optical Response. United States: N. p., 2018. Web. doi:10.1021/acsnano.8b03754.
Gupta, Sunny, Shirodkar, Sharmila N., Kutana, Alex, & Yakobson, Boris I. In Pursuit of 2D Materials for Maximum Optical Response. United States. doi:10.1021/acsnano.8b03754.
Gupta, Sunny, Shirodkar, Sharmila N., Kutana, Alex, and Yakobson, Boris I. Tue . "In Pursuit of 2D Materials for Maximum Optical Response". United States. doi:10.1021/acsnano.8b03754. https://www.osti.gov/servlets/purl/1543718.
@article{osti_1543718,
title = {In Pursuit of 2D Materials for Maximum Optical Response},
author = {Gupta, Sunny and Shirodkar, Sharmila N. and Kutana, Alex and Yakobson, Boris I.},
abstractNote = {Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron–photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance ($A$) and reflectance ($R$) in 2D materials and also conduct a computational survey to seek out those with best $A$ and $R$ in various frequency ranges, from mid-infrared to deep-ultraviolet. We find that 2D boron has broadband reflectance R > 99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe–Salpeter equation. We found several monolayer semiconductors with absorbances ≳30% in different optical ranges, which are more than half of the maximum possible value, Alim = 1/2, for a freestanding 2D material. Our study predicts 2D materials which can potentially be used in ultrathin reflectors and absorbers for optoelectronic application in various frequency ranges.},
doi = {10.1021/acsnano.8b03754},
journal = {ACS Nano},
number = 11,
volume = 12,
place = {United States},
year = {2018},
month = {9}
}

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Figures / Tables:

Figure 1 Figure 1: (a) Reflectance R and transmittance T of a model two-dimensional metal described as a 2D electron gas for electron concentrations n between 1014 and 1018 cm-2. The values for absorbance A in the visible range are small (<0.01) and not shown for clarity. Other fixed parameters are mmore » = me, $\tau$ =30 fs, and kF2 = 2$π$n. (b) Calculated maximum absorbance of a model two-band semiconductor with different joint densities of states ($ρ$cv) depending on the effective masses of the valence ($m$v) and conduction bands ($m$c) as a function of |$m$c–$m$v|. Perfect nesting, $m$c = $m$v; absorbance has a narrow peak with the width inversely proportional to scattering time $\tau$ and maximum value reaching $A$lim = 1/2 (upper right panel). Nearly perfect nesting, $m$c ≠ $m$v and $m$c, $m$v > 0; $A$ < 1/2, and the width of the absorbance peak is proportional to |$m$c–$m$v| (middle right panel). Absorption edge, $m$c ≠ $m$v, $m$c > 0, $m$v < 0, yielding a step-like feature in absorbance (lower right panel).« less

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.