Stress measurements of germanium nanocrystals embedded in silicon oxide

Ge nanocrystals embedded in thermal SiO2 on top of a Si substrate are investigated using Raman spectroscopy and transmission electron microscopy. We observe that the Raman peak frequency of the Ge nanocrystals is strongly affected by compressive stress. In the case of large particles for which the phonon confinement-induced Raman shift can be neglected, the stress is measured taking into account isotopic composition effects induced by the ion implantation process used to produce
the nanocrystals. The stress is proposed to originate from a liquid¿solid phase transition in Ge.