Electron impact induced collective and atomic-like single-electron Ga3d → εl excitations in GaAsN alloy

Nitride nanolayer of about 4 nm thickness formed on the GaAs (1 0 0) surface by N2+ ion bombardment with energy Ei = 2500 eV has been studied in situ by electron energy loss spectroscopy (EELS). Collective (plasmonic) and single-electron excitations were resolved in the EELS spectrum. Analysis of the plasmonic contributions from different chemical phases showed domination of the phase of GaAsN alloy in the nitrated layer. Single-electron excitations were shown to be related to the transitions from core- and valence band states into unoccupied local atomic-like states Ga3d → εl and “GaAs4p” → εl. The model of the atomic-like state formation in a temporary quantum dot near Ga atom was assumed. It has been shown that analysis of collective and single-electron excitations enables synchronous EELS diagnostics of both the chemical composition and unoccupied states of GaAs nitrides.