Size evolution of low energy electron generated Ca colloids in CaF2

Abstract

Metal colloids in CaF2 created by low energy electron irradiation are identified by their optical absorption bands. A mean colloid radius of 18 nm is deduced from a narrow colloid band found in crystals irradiated at room temperature. Absorption data reveal a strong influence of crystal temperature during irradiation on metallization efficiency, mean colloid size, and colloid size distribution. A reversible absorption band shift is observed when turning the electron beam on and off, which may indicate a decrease of colloid size during electron irradiation.