Digenite (Cu9S5): Layered p-Type Semiconductor Grown by Reactive Annealing of Copper

Anat Itzhak, Eti Teblum, Olga Girshevitz, Sivan Okashy, Yury Turkulets, Luba Burlaka, Gili Cohen-Taguri, Efrat Shawat Avraham, Malachi Noked, Ilan Shalish, Gilbert Daniel Nessim

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

Most of the recently discovered layered materials such as MoS2 or MoSe2 are n-type, while few materials, such as phosphorene, which suffers from rapid oxidation, are p-type. To form devices such as p-n junctions and heterojunctions, new p-type mono-/few-layers are needed. Here, we report a one-step synthesis of layered, crystalline, p-type copper sulfide by thermal annealing of a standard copper foil in an inert environment using chemical vapor deposition (CVD). Optical spectroscopies (photoluminescence and absorption) show definite correlating features around 2.5 eV. Surface photovoltage spectroscopy shows a photovoltage reduction around the same energy range, which would be expected from a bandgap of a p-type material, and p-type conductivity was also observed using a thermoelectric probe. TEM, XRD, and AFM showed that the synthesized material is layered and has a unique stoichiometry of Cu9S5. Using sonication and dropcasting, we succeeded to isolate few-layers and monolayers. We observed good bulk electrical conductivity and characterized the electrical conductivity of few-layer copper sulfide flakes using peak force tunneling atomic force microscopy (PF-TUNA). We observed an increase in conductivity for increasing number of layers. Given its conductivity and layered morphology, we tested the synthesized Cu9S5 as an electrode for a Li-ion battery. The proposed bottom-up synthesis, which is simple and scalable, allows synthesizing bulk quantities of the p-type layered Cu9S5 which can then be exfoliated (top-down) to deposit monolayer flakes on substrates. Combined with the progress achieved in the preparation of n-type layered materials, this p-type Cu9S5 opens the door to the fabrication of 2D p-n heterojunctions.

Original languageEnglish
Pages (from-to)2379-2388
Number of pages10
JournalChemistry of Materials
Volume30
Issue number7
DOIs
StatePublished - 10 Apr 2018

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

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