Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The influence of the annealing atmosphere on the temperature induced phase separation of Ge oxide in GeOx/SiO2 multilayers (x ~ 1) leading to size controlled growth of Ge nanocrystals is explored by means of x-ray absorption spectroscopy at the Ge K-edge. Ge sub-oxides contained in the as-deposited multilayers diminish with increasing annealing temperature, showing a complete phase separation at approximately 450 °C using inert N2 ambient. The use of reducing H2 in the annealing atmosphere influences the phase separation even in an early stage of the disproportionation. In particular, the temperature regime where the phase separation occurs is lowered by at least 50 °C. At temperatures above 400 °C the sublayer composition and thus the density of the Ge nanocrystals can be altered by making use of the reduction of GeO2 by H2.