The growth modes of vapor-deposited Bi on Cu(2 1 0)

This work presents growth modes of vapor-deposited Bi on clean and C contaminated Cu(2 1 0) surfaces, characterized with low energy electron diffraction (LEED), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and work-function shifts (Δeφ). Up to θBi=0.5 ML (monolayer, ML) fractional Bi coverage (equivalent to 0.686×1015 at. cm−2) a p(1×1) structure is observed, associated with a gradual LEED pattern symmetry change from one mirror plane for clean Cu(2 1 0) to two, for θBi=0.5 ML. The higher symmetry phase is stable up to 723 K, and no appreciable binding-energy shifts are detected by XPS in the Bi (4f7/2) and Cu (2p3/2) core lines. Additional Bi results in Stranski–Krastanov growth of a compact Cu(2 1 0)–(6×1)-Bi structure with eight Bi atoms per unit cell, stable up to 628 K. Impurity levels of both either pre or coadsorbed C lower the stability temperature of the (6×1)-Bi phase. However, C does not have any appreciable influence on the p(1×1)-Bi phase. The presence of as little as θC=0.1 ML of preadsorbed C produces Frank–Van der Merwe (layer by layer) growth of the p(1×1) c2mm structure, up till completion of the third layer, and as much as 30% variation in Δeφ values with respect to C-free samples. Carbon appears to have no effect on the growth, at 723 K, of Cu(2 1 0)–p(1×1)-Bi facets from the Cu(1 0 0)-c(2×2)–Bi phase when sufficient defects (vacancies) are present in the selvedge.