Growth of Ge nanoparticles on SiO 2/Si interfaces during annealing of plasma enhanced chemical vapor deposited thin films

Abstract

Multilayer germanosilicate (Ge:SiO 2) films have been grown by plasma enhanced chemical vapor deposition. Each Ge:SiO 2 layer is separated by a pure SiO 2 layer. The samples were heat treated at 900 °C for 15 and 45 min. Transmission electron microscopy investigations show precipitation of particles in the layers of highest Ge concentration. Furthermore there is evidence of diffusion between the layers. This paper focuses mainly on observed growth of Ge particles close to the interface, caused by Ge diffusion from the Ge:SiO 2 layer closest to the interface through a pure SiO 2 layer and to the interface. The particles grow as spheres in a direction away from the interface. Particles observed after 15 min anneal time are 4 nm in size and are amorphous, while after 45 min anneal time they are 7 nm in size and have a crystalline diamond type Ge structure.