Chemistry

Quantification of Surface Reactivity and Step-Selective Etching Chemistry on Single-Crystal BiOI(001)

Document Type

Article

Abstract

To bridge the gap between the cleanliness of a freshly cleaved surface of 2D BiOI and that available from a purely chemical-etching means, we subjected single-crystal BiOI to a series of surface treatments and quantified the resulting chemical states and electronic properties. Vapor transport syntheses included both physical vapor transport from single-source BiOI, as well as chemical vapor transport from Bi2O3 + BiI3 and from Bi + I2 + Bi2O3. Surface treatments included tape cleaving, rinsing in water, sonication in acetone, an aqueous HF etch, and a sequential HF etch with subsequent sonication in acetone. X-ray diffraction, XRD, and X-ray photoelectron spectroscopy, XPS, probed the resulting bulk crystalline species and interfacial chemical states, respectively. In comparison with overlayer models of idealized oxide-Terminated or iodide-Terminated BiOI, angle-resolved XPS elucidated surface terminations as a function of each treatment. Ultraviolet photoelectron spectroscopy, UPS, established work-function, and Fermi-level energies for each treatment. Data reveal that HF etching yields interfacial BiI3 at BiOI steps that is subsequently removed with acetone sonication. UPS establishes n-Type behavior for the vapor-Transport-synthesized BiOI, and surface work function and Fermi level shifts for each chemical treatment under study. We discuss the implications for processing BiOI nanofilms for energy-conversion applications.

Publication Title

Langmuir

Publication Date

8-18-2020

Volume

36

Issue

32

First Page

9343

Last Page

9355

ISSN

0743-7463

DOI

10.1021/acs.langmuir.0c00980

Keywords

Acetone, Bismuth compounds, electronic properties, energy conversion, etching, Fermi level, photoelectrons, photons, sonication, transport properties; Ultraviolet photoelectron spectroscopy, work function, X-ray photoelectron spectroscopy

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