Investigating electronic structure of surfaces using Auger mediated positron sticking induced electron spectroscopy

Recent investigations in our lab demonstrated the ability of the new technique Auger mediated positron sticking induced electron spectroscopy (AMPSIES) to probe the electronic structure of the topmost atomic layer. In Auger mediated positron sticking (AMPS), the energy released during the quantum sticking of positrons on the sample surface is coupled to a valence band electron, which may then have enough energy to escape from the sample. Since the Columbic interaction between the positron and the electron during AMPS is highly screened, the probe depth is limited to one angstrom making the technique highly surface selective. Results obtained from the application of the method on single layer graphene on polycrystalline copper and polycrystalline copper after removal of the graphene overlayer provided conclusive proof that the electrons emitted following AMPS originates exclusively from the topmost atomic layer. Our measurements also showed conclusively that the energy spectrum of electrons emitted following AMPS reflects the surface density of states that is weighted by the matrix element of the AMPS process. Here, we report the AMPS induced electron spectra from Au (metal), Si (semi-conductor) and graphite (semi-metal) to demonstrate the applicability of the technique to wider systems and discuss the implications of our findings to surface spectroscopy using positrons.