Copper migration and surface oxidation of CuxBi2Se3 in ambient pressure environments

Abstract

Chemical modifications such as intercalation can be used to modify surface properties or to further functionalize the surface states of topological insulators. Using ambient pressure X-ray photoelectron spectroscopy, we report copper migration in Cux Bi2Se3, 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 modelled 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 topological insulators—and intercalated materials in general—that surface chemical composition can change when specimens are exposed to ambient conditions.

Hafnium, Titanium, and Zirconium Intercalation in 2D Layered Nanomaterials

“…Acquisition of spectra in different sites shows that the intercalants may form domains within the host similar to other intercalants. 2,5,7,35 XPS was used in conjunction with SEM-EDX to determine the average atomic percentage of intercalant. Table 1 provides the atomic percent of the intercalant from XPS measurements.…”

“…This can be from islanding domain formation and/or presence of defects which hinders the effective diffusion of intercalated ions in a crystal. Acquisition of spectra in different sites shows that the intercalants may form domains within the host similar to other intercalants. ,,, …”