Periodic precipitation of crystalline Ge nanoparticles in Ge–B–SiO2 thin glass films

Crystalline 20- to 40-nm-diam Ge nanoparticles were precipitated periodically in Ge–B–SiO2 thin glass films fabricated by the plasma-enhanced chemical vapor deposition method. Such a periodic structure was created by exposure to an interference pattern with a KrF excimer laser (248nm wavelength) and successive annealing at 600°C. Nanoparticles were precipitated predominantly in the unirradiated region after photoinduced refractive index change was erased completely after annealing up to 500°C.