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Observation and enhancement through alkali metal doping of p-type conductivity in the layered oxyselenides Sr2ZnO2Cu2Se2 and Ba2Zn1-xO2-xCu2Se2

Observation and enhancement through alkali metal doping of p-type conductivity in the layered oxyselenides Sr2ZnO2Cu2Se2 and Ba2Zn1-xO2-xCu2Se2
Observation and enhancement through alkali metal doping of p-type conductivity in the layered oxyselenides Sr2ZnO2Cu2Se2 and Ba2Zn1-xO2-xCu2Se2

The optoelectronic properties of two layered copper oxyselenide compounds, with nominal composition Sr 2ZnO 2Cu 2Se 2 and Ba 2ZnO 2Cu 2Se 2, have been investigated to determine their suitability as p-type conductors. The structure, band gaps and electrical conductivity of pristine and alkali-metal-doped samples have been determined. We find that the strontium-containing compound, Sr 2ZnO 2Cu 2Se 2, adopts the expected tetragonal Sr 2 Mn 3 SbO 2 structure with I4/ mmm symmetry, and has a band gap of 2.16 eV, and a room temperature conductivity of 4.8 × 10 -1 S cm -1. The conductivity of the compound could be increased to 4.2 S cm -1 when sodium doped to a nominal composition of Na 0.1Sr 1.9ZnO 2Cu 2Se 2. In contrast, the barium containing material was found to have a small zinc oxide deficiency, with a sample dependent compositional range of Ba 2Zn 1- x O 2- x Cu 2Se 2 where 0.01 < x < 0.06, as determined by single crystal X-ray diffraction and powder neutron diffraction. The barium-containing structure could also be modelled using the tetragonal I4/ mmm structure, but significant elongation of the oxygen displacement ellipsoid along the Zn-O bonds in the average structure was observed. This indicated that the oxide ion position was better modelled as a disordered split site with a displacement to change the local zinc coordination from square planar to linear. Electron diffraction data confirmed that the oxide site in Ba 2Zn 1- x O 2- x Cu 2Se 2 does not adopt a long range ordered arrangement, but also that the idealised I4/ mmm structure with an unsplit oxide site was not consistent with the extra reflections observed in the electron diffractograms. The band gap and conductivity of Ba 2Zn 1- x O 2- x Cu 2Se 2 were determined to be 2.22 eV and 2.0 × 10 -3 S cm -1 respectively. The conductivity could be increased to 1.5 × 10 -1 S cm -1 with potassium doping in K 0.1Ba 1.9Zn 1- x O 2- x Cu 2Se 2. Hall measurements confirmed that both materials were p-type conductors with holes as the dominant charge carriers.

2050-7526
17574-17586
Malik, Zahida
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Broadley, Sarah
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Herkelrath, Sebastian J.C.
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Newbrook, Daniel W.
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Kemp, Liam
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Rutt, George
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Gál, Zoltán A.
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Blandy, Jack N.
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Hadermann, Joke
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Davies, Daniel W.
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Smyth, Robert D.
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Scanlon, David O.
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Huang, Ruomeng
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Clarke, Simon J.
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Hyett, Geoffrey
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Malik, Zahida
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Broadley, Sarah
945aef63-bbd0-4374-a5bc-b4d36f5f19f0
Herkelrath, Sebastian J.C.
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Newbrook, Daniel W.
8eb26553-e1e2-492d-ad78-ce51a487f31f
Kemp, Liam
82904c87-e2d8-410b-b338-aa823636fa11
Rutt, George
81311063-7332-4556-8c2b-2a7f4e8077e7
Gál, Zoltán A.
afa8d04e-0ac4-449d-a724-ff5a4387347c
Blandy, Jack N.
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Hadermann, Joke
1268716b-563f-4a6b-9dbe-cc8149af5e7f
Davies, Daniel W.
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Smyth, Robert D.
86275bf8-8447-4af5-a175-15b3706aed3c
Scanlon, David O.
23dbcc36-0b42-40dc-a3af-64c8bad7beb3
Huang, Ruomeng
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Clarke, Simon J.
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Hyett, Geoffrey
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Malik, Zahida, Broadley, Sarah, Herkelrath, Sebastian J.C., Newbrook, Daniel W., Kemp, Liam, Rutt, George, Gál, Zoltán A., Blandy, Jack N., Hadermann, Joke, Davies, Daniel W., Smyth, Robert D., Scanlon, David O., Huang, Ruomeng, Clarke, Simon J. and Hyett, Geoffrey (2024) Observation and enhancement through alkali metal doping of p-type conductivity in the layered oxyselenides Sr2ZnO2Cu2Se2 and Ba2Zn1-xO2-xCu2Se2. Journal of Materials Chemistry C, 12 (43), 17574-17586. (doi:10.1039/D4TC02458C).

Record type: Article

Abstract

The optoelectronic properties of two layered copper oxyselenide compounds, with nominal composition Sr 2ZnO 2Cu 2Se 2 and Ba 2ZnO 2Cu 2Se 2, have been investigated to determine their suitability as p-type conductors. The structure, band gaps and electrical conductivity of pristine and alkali-metal-doped samples have been determined. We find that the strontium-containing compound, Sr 2ZnO 2Cu 2Se 2, adopts the expected tetragonal Sr 2 Mn 3 SbO 2 structure with I4/ mmm symmetry, and has a band gap of 2.16 eV, and a room temperature conductivity of 4.8 × 10 -1 S cm -1. The conductivity of the compound could be increased to 4.2 S cm -1 when sodium doped to a nominal composition of Na 0.1Sr 1.9ZnO 2Cu 2Se 2. In contrast, the barium containing material was found to have a small zinc oxide deficiency, with a sample dependent compositional range of Ba 2Zn 1- x O 2- x Cu 2Se 2 where 0.01 < x < 0.06, as determined by single crystal X-ray diffraction and powder neutron diffraction. The barium-containing structure could also be modelled using the tetragonal I4/ mmm structure, but significant elongation of the oxygen displacement ellipsoid along the Zn-O bonds in the average structure was observed. This indicated that the oxide ion position was better modelled as a disordered split site with a displacement to change the local zinc coordination from square planar to linear. Electron diffraction data confirmed that the oxide site in Ba 2Zn 1- x O 2- x Cu 2Se 2 does not adopt a long range ordered arrangement, but also that the idealised I4/ mmm structure with an unsplit oxide site was not consistent with the extra reflections observed in the electron diffractograms. The band gap and conductivity of Ba 2Zn 1- x O 2- x Cu 2Se 2 were determined to be 2.22 eV and 2.0 × 10 -3 S cm -1 respectively. The conductivity could be increased to 1.5 × 10 -1 S cm -1 with potassium doping in K 0.1Ba 1.9Zn 1- x O 2- x Cu 2Se 2. Hall measurements confirmed that both materials were p-type conductors with holes as the dominant charge carriers.

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Accepted/In Press date: 9 September 2024
e-pub ahead of print date: 19 September 2024
Published date: 21 November 2024
Additional Information: Publisher Copyright: © 2024 The Royal Society of Chemistry.

Identifiers

Local EPrints ID: 494771
URI: http://eprints.soton.ac.uk/id/eprint/494771
ISSN: 2050-7526
PURE UUID: 13aff98d-d6cb-40eb-920d-96a7e891572f
ORCID for Zahida Malik: ORCID iD orcid.org/0000-0002-1212-6845
ORCID for Daniel W. Newbrook: ORCID iD orcid.org/0000-0002-5047-6168
ORCID for Ruomeng Huang: ORCID iD orcid.org/0000-0003-1185-635X
ORCID for Geoffrey Hyett: ORCID iD orcid.org/0000-0001-9302-9723

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Date deposited: 15 Oct 2024 16:44
Last modified: 30 Nov 2024 03:07

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Contributors

Author: Zahida Malik ORCID iD
Author: Sarah Broadley
Author: Sebastian J.C. Herkelrath
Author: Daniel W. Newbrook ORCID iD
Author: Liam Kemp
Author: George Rutt
Author: Zoltán A. Gál
Author: Jack N. Blandy
Author: Joke Hadermann
Author: Daniel W. Davies
Author: Robert D. Smyth
Author: David O. Scanlon
Author: Ruomeng Huang ORCID iD
Author: Simon J. Clarke
Author: Geoffrey Hyett ORCID iD

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