Proton irradiation of germanium isotope multilayer structures at elevated temperatures

Abstract

Irradiation of germanium (Ge) isotope heterostructures with 2.5 MeV protons have been performed at 550 °C. The applied proton flux was varied between 1.0 and 1.5 μA leading to various rates of Frenkel pair production. After irradiation, concentration profiles of the Ge isotopes were recorded by means of secondary ion mass spectrometry (SIMS). An inhomogeneous broadening of the isotope structure was observed. In addition to the effect of irradiation enhanced self-diffusion, an influence of the formation of microscopic defects on the detected broadening was ascertained. Atomic force and scanning electron microscopy show that the microscopic defects are most probably resulting from an aggregation of vacancies formed during irradiation. Numerical analysis of Ge profiles not disturbed by microdefect formation indicates a significant contribution of self-interstitials to self-diffusion under irradiation.