Dependence of core-level photoemission spectra on overlayer growth mode: Al on InP(110)

The adsorption of Al overlayers on the clean, cleaved InP(110) surface has been studied, with the InP substrates at room and low ({~}120 K) temperatures, using synchrotron radiation excited soft-x-ray photoemission spectroscopy. This interface exhibits a well-documented exchange reaction at room temperature, and a visual comparison of the spectra taken at 300 and 120 K suggests that this reaction is inhibited at 120 K. However, there are also significant changes in the interface growth mode as the temperature is lowered. The reacted indium feature exhibits a coverage-dependent binding energy, so that its spectral weight is obscured by overlap with the bulk indium feature. Moreover, escape-depth considerations invalidate a simple comparison of reactivity at the two temperatures.