TEM studies of Ge nanocrystal formation in PECVD grownSiO2:Ge/SiO2 multilayers

Abstract

We investigate the effect of annealing on the Ge nanocrystal formation in multilayeredgermanosilicate–oxide films grown on Si substrates by plasma enhanced chemical vapour deposition(PECVD). The multilayered samples were annealed at temperatures ranging from 750 to900 °C for 5 min under nitrogen atmosphere. The onset of formation of Ge nanocrystals, at750 °C, can be observed via high resolution TEM micrographs. The diameters of Ge nanocrystalswere observed to be between 5 and 14 nm. As the annealing temperature is raised to850 °C, asecond layer of Ge nanocrystals forms next to the original precipitation band, positioning itself closer to thesubstrate SiO2 interface. High resolution cross section TEM images, electron diffraction and electronenergy-loss spectroscopy as well as energy-dispersive x-ray analysis (EDAX) data allindicate that Ge nanocrystals are present in each layer.