The growth of bismuth and antimony overlayers on InP(110)

Abstract

The adsorption of Bi and Sb on clean cleaved InP(110) surfaces has been studied with soft x-ray photoemission spectroscopy at the BESSY synchrotron radiation source in Berlin. Bi and Sb were deposited onto ultrahigh vacuum cleaved InP(110) surfaces at substrate temperatures of 300 K [room temperature (RT)] and 120 K [low temperature (LT)]. In this paper we focus on the evolution of the overlayer emission intensities as a function of coverage. Spectra of the Bi 5d and Sb 4d core level emission lines were taken from the submonolayer regime up to coverages of approximately 60 and 20 monolayers (ML) of Bi and Sb, respectively. The spectra were then deconvoluted using a core level fitting routine. In all cases, good agreement between the experimental and fitted curves was achieved by introducing two chemically shifted components of the Bi 5d and Sb 4d core level emission which are interpreted in terms of Bi(Sb)–substrate and Bi(Sb)–Bi(Sb) bonds. However, for RT deposition, the evolution of the Bi 5d and Sb 4d spectra is significantly different in the coverage range below 2 ML. In the Bi case the adatom–substrate component grows first, and only after about 0.5 ML is the Bi–Bi component observed. The two components have equal intensity at about 2 ML. In contrast, the two components in the Sb 4d spectra grow with equal intensity until 1 ML. The spectra for higher coverages for both systems are dominated by the component assigned to adatom–adatom bonds and the overlayer is found to be semimetallic. The LT spectra do not have the easily resolvable features seen in the RT spectra which may indicate that the growth is much more disordered. However, the overlayers at LT are more laminar. In addition, we present the band bending versus coverage behavior for the Bi/p-InP(110) interface, which is compared to that of Sb/p-InP(110).