Mater. Res. Soc. Symp. Proc. Vol. 1411 © 2012 Materials Research Society DOI: 10.1557/opl.2012.758 Effects of Ad-atom Diffusivity Throughout Sb-Mediated Formation of Ge/Si Nanoislands Alexander A. Tonkikh 1,2 , Nikolay D. Zakharov 1 , Alexandra A. Suvorova 3 , Peter Werner 1 1 Max Planck Institute of Microstructure Physics, 2 Weinberg, Halle, D-06120, Germany 2 Institute for Physics of Microstructures RAS, Nizhniy Novgorod, GSP-105, Russia 3 Centre for Microscopy, Characterisation and Analysis, the University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia ABSTRACT The effect of Sb on the formation of Ge nano islands in Si by means of molecular beam epitaxy is reported. We observe in the Ge/Si(100) system a non-monotonic dependence of the Stranski-Krastanov critical thickness of Ge islands formation on the adsorbed Sb amount. Dome- and hut-shaped Ge islands are replaced with the pyramids, when Ge is deposited on the Sb- covered Si(100) surface. The Sb-mediated conservation of the shape of Ge islands during embedding them in Si is shown. We assume that the decrease of the surface diffusion of Si and Ge ad-atoms causes these effects. INTRODUCTION Coherent Ge islands embedded in a Si matrix by means of epitaxy attract considerable interest due to the possibility of their application in opto-electronic devices [1]. Since photo- and electroluminescence at room temperature were reported [2, 3], these small Ge insertions in Si have been considered to be a promising active region of a Si based emitter compatible with the CMOS technology. However, the low efficiency of radiative recombination, caused by the inherit lineup of energy bands, usually hinders their use in light emitters. Recently we have shown that intense photo- and electroluminescence are detected at room temperature from the samples with Ge nano islands grown via a thin Sb layer on Si (100) substrates [4, 5]. A higher luminescence intensity of Sb-mediated Ge islands in comparison with Sb-free Ge islands is related to the modification of their structural properties. The subject of the present contribution is the effect of Sb on the structural properties of Ge island arrays. EXPERIMENT The SiGe samples were grown by MBE (Riber SIVA-45) on Si(100) substrates. Deposition rates of Si, Ge and Sb were amounted to 0.5 Å/s, 0.2 Å/s, and 0.013 mono layers (ML) per second, correspondingly. The samples consisted of a 100 nm thick Si buffer layer, a θ- thick Sb layer, and the Ge layer. The samples were investigated in-situ by reflection high energy electron diffraction (RHEED). This search was performed at the substrate temperature of 600 °C to establish the dependence of Stranski-Krastanov critical thickness (h S-K ) on the adsorbed Sb amount (θ). All other samples were investigated ex-situ. They contained a 1.0 nm thick Ge layer. Ex-situ investigations were performed by atomic force microscopy (AFM, Dimension 5000) and cross-section scanning transmission electron microscopy (STEM, TITAN 300/80). The samples used in AFM investigations had Ge islands on their surface formed at growth temperatures of 550, 600, and 650 °C. Three samples used in STEM investigations had Ge islands capped with a