Electronic structure and properties of Cu2-xS thin films : Dependence of phase structures and free-hole concentrations

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Zhan Hua Li
  • Xiao Hu Lv
  • Ying Wang
  • Chao Ping Liu

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Detail(s)

Original languageEnglish
Article number151530
Journal / PublicationApplied Surface Science
Volume572
Online published6 Oct 2021
Publication statusPublished - 15 Jan 2022

Abstract

Cu2-xS has received increasing attentions in recent years, owing to its promising applications in a broad range of optoelectronic devices. However, the phase structures and the electronic structures of Cu2-xS with varying Cu stoichiometries are surprisingly complex, and consensus on these aspects are still lacking. In this work, p-type polycrystalline Cu2-xS thin films with different phase structures and a wide range of free-hole concentrations NHall (1019 ∼ 1022 cm−3) were grown by controlling the Cu stoichiometries. We comprehensively studied the correlation of electronic structures and optoelectrical properties of Cu2-xS thin films with their phase structures and NHall. With increasing NHall of Cu2-xS with different phase structures, it is observed that i) the hole mobility μ reduces from ∼ 6 to ∼ 1 cm2 V−1 s−1; ii) the plasma energy Ep increases from ∼ 0.3 to 1.2 eV; iii) the high-frequency dielectric constant ε decreases linearly from ∼ 10 to ∼ 2.5; iv) the hole effective mass mh increases from ∼ 0.25 to 3.7 m0; v) the direct optical bandgap EGOpt slightly increases from ∼ 1.9 to ∼ 2.45 eV. Our results also reveal that the surface Fermi level of these Cu2-xS thin films is located above the corresponding valence band maximum, likely due to the presence of surface oxidation and/or the surface defects.

Research Area(s)

  • Copper sulfide, Electronic structures, Optoelectronic properties, Phase structures

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