Optical and structural analysis of Ge/Si quantum dots grown on a Si(001) surface covered with a SiO2 sub-monolayer

In this work we performed measurements of photoluminescence (PL), scanning tunneling microscopy (STM), and Rutherford backscattering (RBS) at grazing angles of incidence in a set of samples grown by molecular beam epitaxy, in which a Ge layer was deposited on a Si(001) substrate covered with a thin SiO2 layer. Three different thicknesses for either layer were deposited: 0.5, 0.75 or 1 monolayer (ML) of SiO2, and 0.3, 0.6 or 0.9 nm of Ge. The PL measurements for the samples with thicker layers show a broad band at ∼0.85eV superimposed on a dislocation related band at ∼0.81 eV. The attribution of the high energy band to Ge islands in this sample is supported by STM and RBS measurements, as well as by PL measurements after hydrogen passivation of the sample surface. For the samples with thinner SiO2 and Ge layers, no evidence for the formation of Ge islands was found. © World Scientific Publishing Company.