Effects of Ar+ etching of Cu2ZnSnSe4 thin films: an x-ray photoelectron spectroscopy and photoluminescence study

Michael V. Yakushev, Mikhail A. Sulimov, Ekaterina Skidchenko, Jose Márquez-Prieto, Ian Forbes, Paul R. Edwards, Mikhail V. Kuznetsov, Vadim D. Zhivulko, Olga M. Borodavchenko, Alexander V. Mudryi, Juri Krustok, Robert W. Martin

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Cu2ZnSnSe4 (CZTSe) is a semiconductor used as the absorber layer in highly promising sustainable thin film solar cells. The authors study the effect of Ar+ etching of copper deficient and zinc excess CZTSe thin films deposited on Mo/glass substrates on the surface elemental composition, measured by x-ray photoelectron spectroscopy, and photoluminescence (PL) spectra. Low temperature PL spectra reveal a broad asymmetrical band at 0.95 eV. The temperature and excitation intensity dependencies of this band suggest that it is a free-to-bound (FB) recombination of electrons from the conduction band with holes localized at an acceptor affected by potential fluctuations. The surface composition of the as grown films demonstrates a strong copper deficiency: [Cu]/[Zn + Sn] = 0.33. The etching of the film surface using Ar+ beam increases [Cu]/[Zn + Sn] to 0.51, which is significantly smaller than that of 0.78 in the bulk, measured by wavelength dispersive x-ray analysis, demonstrating the presence on the surface of a copper-depleted layer. The Ar+ etching drastically reduces the FB band intensity by a factor of 4.5, broadens it and develops a low energy tail. Ar ions displace atoms in CZTSe lattice creating primary radiation defects, vacancies, and interstitials, which recombine at room temperature forming antisite defects with deep energy levels. Some of them generate the observed low energy tail and increase the mean depth of potential fluctuation γ, determined from the shape of the low energy side of FB band, from 24 meV before Ar+ etching to 35 meV after. Other deep defects work as nonradiative recombination centers reducing the intensity of the FB band.
LanguageEnglish
Article number061208
Number of pages8
JournalJournal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena
Volume36
DOIs
Publication statusPublished - 2 Nov 2018

Fingerprint

Photoelectron spectroscopy
x ray spectroscopy
Etching
Photoluminescence
etching
photoelectron spectroscopy
photoluminescence
Copper
X rays
Thin films
thin films
Defects
copper
antisite defects
Conduction bands
x ray analysis
Crystal lattices
Surface structure
Temperature
Electron energy levels

Keywords

  • Cu2ZnSnSe4
  • argon ion etching
  • photoluminescence

Cite this

Yakushev, Michael V. ; Sulimov, Mikhail A. ; Skidchenko, Ekaterina ; Márquez-Prieto, Jose ; Forbes, Ian ; Edwards, Paul R. ; Kuznetsov, Mikhail V. ; Zhivulko, Vadim D. ; Borodavchenko, Olga M. ; Mudryi, Alexander V. ; Krustok, Juri ; Martin, Robert W. / Effects of Ar+ etching of Cu2ZnSnSe4 thin films : an x-ray photoelectron spectroscopy and photoluminescence study. In: Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena. 2018 ; Vol. 36.
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abstract = "Cu2ZnSnSe4 (CZTSe) is a semiconductor used as the absorber layer in highly promising sustainable thin film solar cells. The authors study the effect of Ar+ etching of copper deficient and zinc excess CZTSe thin films deposited on Mo/glass substrates on the surface elemental composition, measured by x-ray photoelectron spectroscopy, and photoluminescence (PL) spectra. Low temperature PL spectra reveal a broad asymmetrical band at 0.95 eV. The temperature and excitation intensity dependencies of this band suggest that it is a free-to-bound (FB) recombination of electrons from the conduction band with holes localized at an acceptor affected by potential fluctuations. The surface composition of the as grown films demonstrates a strong copper deficiency: [Cu]/[Zn + Sn] = 0.33. The etching of the film surface using Ar+ beam increases [Cu]/[Zn + Sn] to 0.51, which is significantly smaller than that of 0.78 in the bulk, measured by wavelength dispersive x-ray analysis, demonstrating the presence on the surface of a copper-depleted layer. The Ar+ etching drastically reduces the FB band intensity by a factor of 4.5, broadens it and develops a low energy tail. Ar ions displace atoms in CZTSe lattice creating primary radiation defects, vacancies, and interstitials, which recombine at room temperature forming antisite defects with deep energy levels. Some of them generate the observed low energy tail and increase the mean depth of potential fluctuation γ, determined from the shape of the low energy side of FB band, from 24 meV before Ar+ etching to 35 meV after. Other deep defects work as nonradiative recombination centers reducing the intensity of the FB band.",
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author = "Yakushev, {Michael V.} and Sulimov, {Mikhail A.} and Ekaterina Skidchenko and Jose M{\'a}rquez-Prieto and Ian Forbes and Edwards, {Paul R.} and Kuznetsov, {Mikhail V.} and Zhivulko, {Vadim D.} and Borodavchenko, {Olga M.} and Mudryi, {Alexander V.} and Juri Krustok and Martin, {Robert W.}",
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Effects of Ar+ etching of Cu2ZnSnSe4 thin films : an x-ray photoelectron spectroscopy and photoluminescence study. / Yakushev, Michael V.; Sulimov, Mikhail A.; Skidchenko, Ekaterina; Márquez-Prieto, Jose; Forbes, Ian; Edwards, Paul R.; Kuznetsov, Mikhail V.; Zhivulko, Vadim D.; Borodavchenko, Olga M.; Mudryi, Alexander V.; Krustok, Juri; Martin, Robert W.

In: Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, Vol. 36, 061208, 02.11.2018.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effects of Ar+ etching of Cu2ZnSnSe4 thin films

T2 - Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

AU - Yakushev, Michael V.

AU - Sulimov, Mikhail A.

AU - Skidchenko, Ekaterina

AU - Márquez-Prieto, Jose

AU - Forbes, Ian

AU - Edwards, Paul R.

AU - Kuznetsov, Mikhail V.

AU - Zhivulko, Vadim D.

AU - Borodavchenko, Olga M.

AU - Mudryi, Alexander V.

AU - Krustok, Juri

AU - Martin, Robert W.

PY - 2018/11/2

Y1 - 2018/11/2

N2 - Cu2ZnSnSe4 (CZTSe) is a semiconductor used as the absorber layer in highly promising sustainable thin film solar cells. The authors study the effect of Ar+ etching of copper deficient and zinc excess CZTSe thin films deposited on Mo/glass substrates on the surface elemental composition, measured by x-ray photoelectron spectroscopy, and photoluminescence (PL) spectra. Low temperature PL spectra reveal a broad asymmetrical band at 0.95 eV. The temperature and excitation intensity dependencies of this band suggest that it is a free-to-bound (FB) recombination of electrons from the conduction band with holes localized at an acceptor affected by potential fluctuations. The surface composition of the as grown films demonstrates a strong copper deficiency: [Cu]/[Zn + Sn] = 0.33. The etching of the film surface using Ar+ beam increases [Cu]/[Zn + Sn] to 0.51, which is significantly smaller than that of 0.78 in the bulk, measured by wavelength dispersive x-ray analysis, demonstrating the presence on the surface of a copper-depleted layer. The Ar+ etching drastically reduces the FB band intensity by a factor of 4.5, broadens it and develops a low energy tail. Ar ions displace atoms in CZTSe lattice creating primary radiation defects, vacancies, and interstitials, which recombine at room temperature forming antisite defects with deep energy levels. Some of them generate the observed low energy tail and increase the mean depth of potential fluctuation γ, determined from the shape of the low energy side of FB band, from 24 meV before Ar+ etching to 35 meV after. Other deep defects work as nonradiative recombination centers reducing the intensity of the FB band.

AB - Cu2ZnSnSe4 (CZTSe) is a semiconductor used as the absorber layer in highly promising sustainable thin film solar cells. The authors study the effect of Ar+ etching of copper deficient and zinc excess CZTSe thin films deposited on Mo/glass substrates on the surface elemental composition, measured by x-ray photoelectron spectroscopy, and photoluminescence (PL) spectra. Low temperature PL spectra reveal a broad asymmetrical band at 0.95 eV. The temperature and excitation intensity dependencies of this band suggest that it is a free-to-bound (FB) recombination of electrons from the conduction band with holes localized at an acceptor affected by potential fluctuations. The surface composition of the as grown films demonstrates a strong copper deficiency: [Cu]/[Zn + Sn] = 0.33. The etching of the film surface using Ar+ beam increases [Cu]/[Zn + Sn] to 0.51, which is significantly smaller than that of 0.78 in the bulk, measured by wavelength dispersive x-ray analysis, demonstrating the presence on the surface of a copper-depleted layer. The Ar+ etching drastically reduces the FB band intensity by a factor of 4.5, broadens it and develops a low energy tail. Ar ions displace atoms in CZTSe lattice creating primary radiation defects, vacancies, and interstitials, which recombine at room temperature forming antisite defects with deep energy levels. Some of them generate the observed low energy tail and increase the mean depth of potential fluctuation γ, determined from the shape of the low energy side of FB band, from 24 meV before Ar+ etching to 35 meV after. Other deep defects work as nonradiative recombination centers reducing the intensity of the FB band.

KW - Cu2ZnSnSe4

KW - argon ion etching

KW - photoluminescence

UR - https://avs.scitation.org/journal/jvb

U2 - 10.1116/1.5050243

DO - 10.1116/1.5050243

M3 - Article

VL - 36

JO - Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

JF - Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

SN - 2166-2746

M1 - 061208

ER -