In-situ determination of lattice expansion in proton-bombarded GaP single crystals

Abstract The lattice expansion of GaP, irradiated by 0.3–1.4 MeV protons at 140–715 K was studied in situ by means of the proton- induced Kossel effect. The measurements characterize the surface layer of the crystal with a thickness of 1–2μm. The increase of interplanar spacing Δd{111} measured at T ≥ RT follows a “sublinear” dose-relation with saturation at higher doses. The different initial slopes of the curves obtained at various incidence energies can be described by the energy dependence of the elastic displacement cross section. Measurements performed at T < RT exhibit a more linear “expansion-dose” dependence with a higher expansion rate. As shown by channeling backscattering analysis at RT, the damage density increases with the proton dose in the same manner as the lattice expansion. The expansion was also investigated using X-ray topographs and electron-induced Kossel patterns, confirming the in-situ results.