FORMATION OF GE NANOCRYSTALS IN AMORPHOUS CEOX AND SIGEOX ALLOY-FILMS

We present a systematic analysis of the conditions for the formation o f Ge nanocrystals in GeOx and SiGeOx alloy films during annealing. Amo rphous SiOx, GeOx and SiGeOx alloy films prepared by d.c. magnetron sp uttering were subsequently annealed for times between 10 min and Ga mi n and at annealing temperatures ranging from 350 degrees C up to 800 d egrees C. The formation nanocrystals is analysed by X-ray scattering u nder grazing incidence. No crystallisation is found for the Sig, films under any annealing conditions. On the other hand, clear evidence for the formation of Ge nanocrystals is found in the GeOx as well as in t he SiGeOx films. For the GeOx films the particle diameter d(s) linearl y decreases with increasing oxygen content yielding values of d(s) = 4 0 nm down to 10 nm. The as-prepared amorphous SiGeOx films were found to always consist of nanoamorphous Ge clusters in an amorphous SiOx ma trix determining the size of the resulting Ge nanocrystal after anneal ing. A Ge nanocrystal diameter of around d(s) = 6.0 nm is found for al l SiCeOx alloy films independent of the annealing time and temperature .