Proton-implantation-induced nanosized Ge crystal formation in SiO2:GeO2 glasses

Nanometer-sized crystalline Ge colloid particles in 9SiO2–1GeO2 glasses were formed by implantation of protons at 1.5 MeV without post-thermal annealing. Although oxygen-deficient type point defects associated with Ge ions were primarily formed to fluences ≲1×1017 cm−2, the formation of Ge fine crystalline particles was observed for fluences ≳5×1017 cm−2. No formation of Ge colloids and the Ge-related point defects were noted for implantation of 1.5 MeV He+ to a fluence of 1×1018 cm−2. The depth of Ge colloid formation layers was 22–26 μm from the implanted surface. This depth region agreed well with the peak region of electronic energy deposition. Ge–OH groups were formed preferentially over Si–OH groups upon implantation of protons and the decay curve upon isochronal annealing was close to that of the optical absorption at ∼3 eV, which was attributed to nanometer-sized Ge. A red photoluminescence peaking at ∼1.9 eV was observed for all the implanted substrates. A tentative formation mechanism of Ge colloids in these glasses was proposed.