Improvement in the mechanical performance of Czochralski silicon under indentation by germanium doping

The mechanical properties of germanium-doped Czochralski (GCz) silicon have been investigated using instrumented nanoindentation combined with an ultrasonic pulse-echo overlap technique. The GCz silicon samples showed higher Young's modulus and hardness than germanium-free Czochralski silicon samples in nanoindentation tests. We believe this was caused by the enhanced phase transition from the Si-I phase to the stiffer Si-II phase in GCz silicon under contact load during indentation. This scenario was further confirmed by micro-Raman spectroscopy measurements. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.