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Title: Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitride Cu 3 N

Abstract

The temperature-dependence of the direct band gap and thermal expansion in the metastable anti-ReO 3 semiconductor Cu 3N are investigated between 4.2 and 300 K by Fourier-transform infrared spectroscopy and x-ray diffraction. Complementary refractive index spectra are determined by spectroscopic ellipsometry at 300K. A direct gap of 1.68eV is associated with the absorption onset at 300K, which strengthens continuously and reaches a magnitude of 3.5 x 10 5cm -1 at 2.7eV, suggesting potential for photovoltaic applications. Notably, the direct gap redshifts by just 24meV between 4.2 and 300K, giving an atypically small band-gap temperature coefficient dE g/dT of -0.082meV/K. Additionally, the band structure, dielectric function, phonon dispersion, linear expansion, and heat capacity are calculated using density functional theory; remarkable similarities between the experimental and calculated refractive index spectra support the accuracy of these calculations, which indicate beneficially low hole effective masses and potential negative thermal expansion below 50K. To assess the lattice expansion contribution to the band-gap temperature-dependence, a quasiharmonic model fit to the observed lattice contraction finds a monotonically decreasing linear expansion (descending past 10 -6K -1 below 80K), while estimating the Debye temperature, lattice heat capacity, and Gruneisen parameter. Accounting for lattice and electron-phonon contributions to the observedmore » band-gap evolution suggests average phonon energies that are qualitatively consistent with predicted maxima in the phonon density of states. Furthermore, as band-edge temperature-dependence has significant consequences for device performance, copper nitride should be well suited for applications that require a largely temperature-invariant band gap.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [1];  [1];  [1];  [1];  [1];  [6];  [3];  [1]
  1. Univ. of Liverpool, Liverpool (United Kingdom)
  2. Univ. College London, London (United Kingdom)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  4. European Synchrotron Radiation Facility (ESRF), Grenoble (France)
  5. Univ. of Manchester, Manchester (United Kingdom)
  6. Univ. College London, London (United Kingdom); Diamond Light Source, Ltd., Didcot (United Kingdom)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1345850
Alternate Identifier(s):
OSTI ID: 1350016
Report Number(s):
NREL/JA-5J00-68256
Journal ID: ISSN 2469-9950; PRBMDO; TRN: US1700646
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Published Article
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 11; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; direct band gap; temperature dependence; thermal expansion

Citation Formats

Birkett, Max, Savory, Christopher N., Fioretti, Angela N., Thompson, Paul, Muryn, Christopher A., Weerakkody, A. D., Mitrovic, I. Z., Hall, S., Treharne, Rob, Dhanak, Vin R., Scanlon, David O., Zakutayev, Andriy, and Veal, Tim D.. Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitride Cu3N. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.115201.
Birkett, Max, Savory, Christopher N., Fioretti, Angela N., Thompson, Paul, Muryn, Christopher A., Weerakkody, A. D., Mitrovic, I. Z., Hall, S., Treharne, Rob, Dhanak, Vin R., Scanlon, David O., Zakutayev, Andriy, & Veal, Tim D.. Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitride Cu3N. United States. doi:10.1103/PhysRevB.95.115201.
Birkett, Max, Savory, Christopher N., Fioretti, Angela N., Thompson, Paul, Muryn, Christopher A., Weerakkody, A. D., Mitrovic, I. Z., Hall, S., Treharne, Rob, Dhanak, Vin R., Scanlon, David O., Zakutayev, Andriy, and Veal, Tim D.. Mon . "Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitride Cu3N". United States. doi:10.1103/PhysRevB.95.115201.
@article{osti_1345850,
title = {Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitride Cu3N},
author = {Birkett, Max and Savory, Christopher N. and Fioretti, Angela N. and Thompson, Paul and Muryn, Christopher A. and Weerakkody, A. D. and Mitrovic, I. Z. and Hall, S. and Treharne, Rob and Dhanak, Vin R. and Scanlon, David O. and Zakutayev, Andriy and Veal, Tim D.},
abstractNote = {The temperature-dependence of the direct band gap and thermal expansion in the metastable anti-ReO3 semiconductor Cu3N are investigated between 4.2 and 300 K by Fourier-transform infrared spectroscopy and x-ray diffraction. Complementary refractive index spectra are determined by spectroscopic ellipsometry at 300K. A direct gap of 1.68eV is associated with the absorption onset at 300K, which strengthens continuously and reaches a magnitude of 3.5 x 105cm-1 at 2.7eV, suggesting potential for photovoltaic applications. Notably, the direct gap redshifts by just 24meV between 4.2 and 300K, giving an atypically small band-gap temperature coefficient dEg/dT of -0.082meV/K. Additionally, the band structure, dielectric function, phonon dispersion, linear expansion, and heat capacity are calculated using density functional theory; remarkable similarities between the experimental and calculated refractive index spectra support the accuracy of these calculations, which indicate beneficially low hole effective masses and potential negative thermal expansion below 50K. To assess the lattice expansion contribution to the band-gap temperature-dependence, a quasiharmonic model fit to the observed lattice contraction finds a monotonically decreasing linear expansion (descending past 10-6K-1 below 80K), while estimating the Debye temperature, lattice heat capacity, and Gruneisen parameter. Accounting for lattice and electron-phonon contributions to the observed band-gap evolution suggests average phonon energies that are qualitatively consistent with predicted maxima in the phonon density of states. Furthermore, as band-edge temperature-dependence has significant consequences for device performance, copper nitride should be well suited for applications that require a largely temperature-invariant band gap.},
doi = {10.1103/PhysRevB.95.115201},
journal = {Physical Review B},
number = 11,
volume = 95,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2017},
month = {Mon Mar 06 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevB.95.115201

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Cited by: 1work
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  • The temperature-dependence of the direct band gap and thermal expansion in the metastable anti-ReO 3 semiconductor Cu 3N are investigated between 4.2 and 300 K by Fourier-transform infrared spectroscopy and x-ray diffraction. Complementary refractive index spectra are determined by spectroscopic ellipsometry at 300K. A direct gap of 1.68eV is associated with the absorption onset at 300K, which strengthens continuously and reaches a magnitude of 3.5 x 10 5cm -1 at 2.7eV, suggesting potential for photovoltaic applications. Notably, the direct gap redshifts by just 24meV between 4.2 and 300K, giving an atypically small band-gap temperature coefficient dE g/dT of -0.082meV/K. Additionally,more » the band structure, dielectric function, phonon dispersion, linear expansion, and heat capacity are calculated using density functional theory; remarkable similarities between the experimental and calculated refractive index spectra support the accuracy of these calculations, which indicate beneficially low hole effective masses and potential negative thermal expansion below 50K. To assess the lattice expansion contribution to the band-gap temperature-dependence, a quasiharmonic model fit to the observed lattice contraction finds a monotonically decreasing linear expansion (descending past 10 -6K -1 below 80K), while estimating the Debye temperature, lattice heat capacity, and Gruneisen parameter. Accounting for lattice and electron-phonon contributions to the observed band-gap evolution suggests average phonon energies that are qualitatively consistent with predicted maxima in the phonon density of states. Furthermore, as band-edge temperature-dependence has significant consequences for device performance, copper nitride should be well suited for applications that require a largely temperature-invariant band gap.« less
  • Cited by 4
  • Here we report prediction of two new ternary chalcogenides that can potentially be used as p-type transparent conductors along with experimental synthesis and initial characterization of these previously unknown compounds, Cs 2Zn 3Ch 4 (Ch = Se, Te). In particular, the structures are predicted based on density functional calculations and confirmed by experiments. Phase diagrams, electronic structure, optical properties, and defect properties of Cs 2Zn 3Se 4 and Cs 2Zn 3Te 4 are calculated to assess the viability of these materials as p-type TCMs. Cs 2Zn 3Se 4 and Cs 2Zn 3Te 4, which are stable under ambient air, displaymore » large optical band gaps (calculated to be 3.61 and 2.83 eV, respectively) and have small hole effective masses (0.5-0.77 m e) that compare favorably with other proposed p-type TCMs. Defect calculations show that undoped Cs2Zn3Se4 and Cs2Zn3Te4 are p-type materials. However, the free hole concentration may be limited by low-energy native donor defects, e.g., Zn interstitials. Lastly, non-equilibrium growth techniques should be useful for suppressing the formation of native donor defects, thereby increasing the hole concentration.« less