Synthesis of Si-Ge nanoscale structures via deposition of single-source (GeH ₃) _4-nSiH _n hydrides

Growth of nanoscale islands with distinct Si0.33 Ge0.67, Si0.25 Ge0.75, and Si0.20 Ge0.80 compositions and uniform sizes is conducted on Si(100) via dehydrogenation of the single-source hydrides (H3 Ge)2 SiH2, (H3 Ge)3 SiH, and (H3 Ge)4 Si, respectively. High-spatial-resolution electron energy loss spectroscopy and Raman spectroscopy indicate homogeneous elemental concentrations within and among islands and confirm that their Si-Ge content is predetermined by the stoichiometry of the corresponding precursors. Z-contrast electron microscopy reveals distinct and perfectly epitaxial islands with atomically sharp interfaces grown via a smooth and continuous wetting layer ∼10 Å thick. Cross-sectional electron microscopy shows monomodal distributions of islands with defect-free microstructures. Low-energy electron microscopy studies of the film formation reveal that the growth proceeds via the Stranski-Krastanov mode. Assemblies of coherent quantum dots with highly controlled Ge-rich concentrations produced by this method are desirable for their potentially useful optical properties.