Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3-xSe2

Alexander J.E. Rettie, Mihai Sturza, Christos D. Malliakas, Antia S. Botana, Duck Young Chung, Mercouri G Kanatzidis

Research output: Contribution to journalArticle

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Abstract

The two-dimensional material KCu3-xSe2 was synthesized using both a K2Se3 flux and directly from the elements. It crystallizes in the CsAg3S2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu3-xSe2]- layers separated by K+ ions. Thermal analysis indicated that KCu3-xSe2 melts congruently at ∼755 °C. UV-vis spectroscopy showed an optical band gap of ∼1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurements on single crystals yielded an in-plane resistivity of ∼6 × 10-1 ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K-1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm2 V-1 s-1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ∼ 1019 cm-3) in this material. Electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.

Original languageEnglish
Pages (from-to)6114-6121
Number of pages8
JournalChemistry of Materials
Volume29
Issue number14
DOIs
Publication statusPublished - Jul 25 2017

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Vacancies
Copper
Single crystals
Ions
Semiconductor materials
Seebeck coefficient
Optical band gaps
Valence bands
Ultraviolet spectroscopy
Band structure
Thermoanalysis
Electronic structure
Doping (additives)
Fluxes
Defects
Electrons
Temperature

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Cite this

Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3-xSe2. / Rettie, Alexander J.E.; Sturza, Mihai; Malliakas, Christos D.; Botana, Antia S.; Chung, Duck Young; Kanatzidis, Mercouri G.

In: Chemistry of Materials, Vol. 29, No. 14, 25.07.2017, p. 6114-6121.

Research output: Contribution to journalArticle

Rettie, Alexander J.E. ; Sturza, Mihai ; Malliakas, Christos D. ; Botana, Antia S. ; Chung, Duck Young ; Kanatzidis, Mercouri G. / Copper Vacancies and Heavy Holes in the Two-Dimensional Semiconductor KCu3-xSe2. In: Chemistry of Materials. 2017 ; Vol. 29, No. 14. pp. 6114-6121.
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AB - The two-dimensional material KCu3-xSe2 was synthesized using both a K2Se3 flux and directly from the elements. It crystallizes in the CsAg3S2 structure (monoclinic space group C2/m with a = 15.417(3) Å, b = 4.0742(8) Å, c = 8.3190(17) Å, and β = 112.94(3)°), and single-crystal refinement revealed infinite copper-deficient [Cu3-xSe2]- layers separated by K+ ions. Thermal analysis indicated that KCu3-xSe2 melts congruently at ∼755 °C. UV-vis spectroscopy showed an optical band gap of ∼1.35 eV that is direct in nature, as confirmed by electronic structure calculations. Electronic transport measurements on single crystals yielded an in-plane resistivity of ∼6 × 10-1 ω cm at 300 K that has a complex temperature dependence. The results of Seebeck coefficient measurements were consistent with a doped p-type semiconductor (S = +214 μV K-1 at 300 K), with doping being attributed to copper vacancies. Transport is dominated by low-mobility (on the order of 1 cm2 V-1 s-1) holes caused by relatively flat valence bands with substantial Cu 3d character and a significant concentration of Cu ion vacancy defects (p ∼ 1019 cm-3) in this material. Electronic band structure calculations showed that electrons should be significantly more mobile in this structure type.

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