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

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 BiO + BiI and from Bi + I + BiO. 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.