Core-level photoelectron spectroscopy from individual heteroepitaxial nanocrystals on GaAs(001)

Core-level spectra of individual heteroepitaxial nanocrystals were measured with a spectroscopic photoemission and low-energy electron microscope that allows laterally resolved photoemission spectroscopy. The nanocrystals were obtained by depositing nominally 2 monolayers (ML) of InAs on a Se-terminated GaAs(001) surface. The Se-termination of GaAs results in the formation of a 2–3-ML-thick film of ${\mathrm{Ga}}_2{\mathrm{Se}}_3$ on top of bulk GaAs. During heteroepitaxy the InAs reacts with the ${\mathrm{Ga}}_2{\mathrm{Se}}_3:$ A phase separation takes place on the anion sublattice, while an alloying takes place on the cation sublattice. During the initial stages of growth, a submonolayer-thick wetting layer of ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ is formed that is covered by $({\mathrm{In}}_y{\mathrm{Ga}}_{1-y}{)}_2{\mathrm{Se}}_3.$ $({\mathrm{In}}_y{\mathrm{Ga}}_{1-y}{)}_2{\mathrm{Se}}_3$-covered InAs nanocrystals are formed on this surface.