Optical and structural study of Ge/Si quantum dots on Si(1 0 0) surface covered with a thin silicon oxide layer

The formation of Ge quantum dots (QDs) grown on an ultrathin interlayer of SiO2 on top of a Si(1 0 0) substrate was investigated, as a function of the thicknesses of the SiO2 interlayer (0.5, 0.75 or 1 monolayer (ML)) and the Ge layer (0.3, 0.6 or 0.9 nm). The structural characterization was performed by Rutherford backscattering spectroscopy (RBS). Photoluminescence (PL) studies were done to characterize the optical behavior of all samples. Hydrogen treatment was performed in order to passivate non-radiative recombination channels, thus enhancing the PL intensity. The results suggest the formation of Ge nanoislands (quantum dots, QDs), for the sample with 1 ML of SiO2 and 0.9 nm of Ge, and exclude their formation for samples with lower SiO2 and Ge layer thicknesses. We also observe an influence of the SiO2 interlayer thickness in the QDs formation.