Raman scattering studies in two kinds of Ge nanosystems under hydrostatic pressure

We report Raman scattering of Ge nanocrystals (NCs) embedded in SiO2 matrix on Si substrate (Ge/SiO2/Si) and on quartz substrate (Ge/SiO2/quartz) under hydrostatic pressure. The pressure coefficient obtained for the Ge mode in the Ge/SiO2/quartz nanosystem is found to be almost twice as large compared with its corresponding bulk value. We explained our results using a simple elastic model, which describes the effective pressure transmitted from the matrix to the NCs. In Ge/SiO2/Si nanosystem, delamination of the SiO2 film from the Si substrate occurs at similar to23 kbar due to the large difference between the compressibility of the SiO2 matrix and Si substrate. The observed effect can be understood by the nonhomogeneous distribution of the elastic field in the Ge/SiO2/Si nanosystem using a finite element analysis.