This work presents the structural characterization of nanoclusters formed from a-Si:H/Ge heterostructures processed by rapid thermal annealing (RTA) at 1000 degrees C for annealing times varying between 30 s and 70 s. The a-Si: H layers were grown on electron cyclotron resonance (ECR) using SiH4 and Ar precursor gases. The Ge layer was grown in an e-beam evaporation system. The structural characterizations were performed by high-resolution X-ray diffractometer (HRXRD) on grazing incidence X-ray reflection mode (GIXRR) and micro-Raman measurements. The average grain size, Ge concentration (chi(Ge)) and strain were estimated from Lorentzian GIXRR peak fit. The average grain size varied from 3 nm to 7.5 nm and decreased with annealing time. The chi(Ge) increase with annealing time and varied from 8% to 19%, approximately. The strain calculated for (1 1 1), (2 2 0) and (3 1 1) peaks at 40 s, 50 s, 60 s and 70 s annealing time suggest the geometrical changes in nanoclusters according to process time. (c) 2008 Elsevier B.V. All rights reserved.