Interaction of positrons with the surface of a silicon single crystal
Gol'danskii V. I. , Novikov Yu. A., Rakov A. V., Shantarovich V. P.
The existence of bound states of positrons at a silicon surface has been observed. Such states are possible only for/?-type silicon, produced by doping with boron, beginning at carrier densities ρ ~ 1016 cm ~3. These states are explained in terms of a change in the sign of the positron work function φ+ upon a change in t he carrier density.