4.5 Article

Copper migration and surface oxidation of CuxBi2Se3 in ambient pressure environments

Journal

JOURNAL OF PHYSICS-MATERIALS
Volume 5, Issue 4, Pages -

Publisher

IOP Publishing Ltd
DOI: 10.1088/2515-7639/ac93b5

Keywords

XPS; ambient pressure XPS; topological insulator; intercalated materials

Funding

  1. Laboratory Directed Research and Development (LDRD) Program at Lawrence Berkeley National Laboratory
  2. Alfred P Sloan Foundation [FG-2019-12170]
  3. Humboldt Foundation, Bonn, Germany
  4. National Science Foundation [NSF-DMR-MRI-1828238]
  5. AFOSR [FA9550-18-1-0156]
  6. US Department of Energy Office of Science User Facility [DE-AC02-05CH11231]
  7. UC Lab Fees Research Program [LFR-20-653926]
  8. UC Davis Physics Liquid Helium Laboratory Fund
  9. [NSF-DMR-1838532]

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Using ambient pressure x-ray photoelectron spectroscopy, this study reveals the phenomenon of copper migration in CuxBi2Se3, which is accompanied by oxidation of the sample surface and significant changes in selenium content. The results suggest that surface chemical composition of intercalated TIs may change when exposed to ambient conditions.
Chemical modifications such as intercalation can be used to modify surface properties or to further functionalize the surface states of topological insulators (TIs). Using ambient pressure x-ray photoelectron spectroscopy, we report copper migration in CuxBi2Se3, which occurs on a timescale of hours to days after initial surface cleaving. The increase in near-surface copper proceeds along with the oxidation of the sample surface and large changes in the selenium content. These complex changes are further modeled with core-level spectroscopy simulations, which suggest a composition gradient near the surface which develops with oxygen exposure. Our results shed light on a new phenomenon that must be considered for intercalated TIs-and intercalated materials in general-that surface chemical composition can change when specimens are exposed to ambient conditions.

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