Microstructural investigation of ion beam synthesised germanium nanoclusters embedded in SiO2 layers

Ion beam synthesised Ge nanoclusters in amorphous SiO2 layers were produced by ion implantation and subsequent annealing and investigated by cross section transmission electron microscopy (TEM). After annealing in inert atmosphere at appropriate temperatures, a Ge cluster band with sharp transitions regions appear around the projected range of the implantation profile. The size of the Ge nanoclusters in the band varies from a few nanometers at the transition regions up to about 10 nm in the middle of the band and depends strongly on the annealing temperature and time. The Ge clusters are crystalline with a lattice constant slightly higher than that of Ge bulk material. Much larger Ge clusters line up far from the maximum of the implantation profile (position of the mean projected range) have diameters up to 40 nm if the annealing conditions were changed to an H-2 containing atmosphere. The results of cross section TEM are supported by scanning TEM analysis combined with an energy dispersive X-ray detection system and RES investigations. (C) 1998 Elsevier Science B.V. All rights reserved.