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Title: Monte Carlo simulations of disorder in ZnSn N 2 and the effects on the electronic structure

Abstract

In multinary compound semiconductors, cation disorder can decisively alter the electronic properties and impact potential applications. ZnSnN 2 is a ternary nitride of interest for photovoltaics, which forms in a wurtzite-derived crystal structure. In the ground state, every N anion is coordinated by two Zn and two Sn cations, thereby observing the octet rule locally. Using a motif-based model Hamiltonian, we performed Monte Carlo simulations that provide atomistic representations of ZnSnN 2 with varying degrees of cation disorder. Subsequent electronic structure calculations describe the evolution of band gaps, optical properties, and carrier localization effects as a function of the disorder. We find that octet-rule conserving disorder is practically impossible to avoid but perfectly benign, with hardly any effects on the electronic structure. In contrast, a fully random cation distribution would be very detrimental, but fortunately it is energetically highly unfavorable. A degree of disorder that can realistically be expected for nonequilibrium thin-film deposition leads to a moderate band-gap reduction and to moderate carrier localization effects. Comparing the simulated structures with experimental samples grown by sputtering, we find evidence that these samples indeed incorporate a certain degree of octet-rule violating disorder, which is reflected in the x-ray diffraction and in themore » optical absorption spectra. This study demonstrates that the electronic properties of ZnSnN 2 are dominated by changes of the local coordination environments rather than long-range ordering effects.« less

Authors:
 [1];  [2];  [1];  [3];  [2];  [1];  [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1415121
Report Number(s):
NREL/JA-5K00-68918
Journal ID: ISSN 2475-9953; PRMHAR
Grant/Contract Number:
AC36-08GO28308; AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 3; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; photovoltaics; electronic structure; Monte Carlo simulation

Citation Formats

Lany, Stephan, Fioretti, Angela N., Zawadzki, Paweł P., Schelhas, Laura T., Toberer, Eric S., Zakutayev, Andriy, and Tamboli, Adele C. Monte Carlo simulations of disorder in ZnSnN2 and the effects on the electronic structure. United States: N. p., 2017. Web. doi:10.1103/PhysRevMaterials.1.035401.
Lany, Stephan, Fioretti, Angela N., Zawadzki, Paweł P., Schelhas, Laura T., Toberer, Eric S., Zakutayev, Andriy, & Tamboli, Adele C. Monte Carlo simulations of disorder in ZnSnN2 and the effects on the electronic structure. United States. doi:10.1103/PhysRevMaterials.1.035401.
Lany, Stephan, Fioretti, Angela N., Zawadzki, Paweł P., Schelhas, Laura T., Toberer, Eric S., Zakutayev, Andriy, and Tamboli, Adele C. 2017. "Monte Carlo simulations of disorder in ZnSnN2 and the effects on the electronic structure". United States. doi:10.1103/PhysRevMaterials.1.035401.
@article{osti_1415121,
title = {Monte Carlo simulations of disorder in ZnSnN2 and the effects on the electronic structure},
author = {Lany, Stephan and Fioretti, Angela N. and Zawadzki, Paweł P. and Schelhas, Laura T. and Toberer, Eric S. and Zakutayev, Andriy and Tamboli, Adele C.},
abstractNote = {In multinary compound semiconductors, cation disorder can decisively alter the electronic properties and impact potential applications. ZnSnN2 is a ternary nitride of interest for photovoltaics, which forms in a wurtzite-derived crystal structure. In the ground state, every N anion is coordinated by two Zn and two Sn cations, thereby observing the octet rule locally. Using a motif-based model Hamiltonian, we performed Monte Carlo simulations that provide atomistic representations of ZnSnN2 with varying degrees of cation disorder. Subsequent electronic structure calculations describe the evolution of band gaps, optical properties, and carrier localization effects as a function of the disorder. We find that octet-rule conserving disorder is practically impossible to avoid but perfectly benign, with hardly any effects on the electronic structure. In contrast, a fully random cation distribution would be very detrimental, but fortunately it is energetically highly unfavorable. A degree of disorder that can realistically be expected for nonequilibrium thin-film deposition leads to a moderate band-gap reduction and to moderate carrier localization effects. Comparing the simulated structures with experimental samples grown by sputtering, we find evidence that these samples indeed incorporate a certain degree of octet-rule violating disorder, which is reflected in the x-ray diffraction and in the optical absorption spectra. This study demonstrates that the electronic properties of ZnSnN2 are dominated by changes of the local coordination environments rather than long-range ordering effects.},
doi = {10.1103/PhysRevMaterials.1.035401},
journal = {Physical Review Materials},
number = 3,
volume = 1,
place = {United States},
year = 2017,
month = 8
}

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