Atomistic Aspects of Sige Nanostructure Formation by Molecular-Beam Epitaxy
Based on experimental data obtained with high-energy electron- diffraction (RHEED) and in situ scanning tunneling microscopy, the formation mechanism of the Ge wetting layer on Si(001) and Si(111) is presented. It is shown that the first Ge nanoclusters containing up to several tens of atoms nucleate predominantly on substrate surface defects and on domain boundaries of Si(111)-7×7 and Si(001)-2×l. For the Si(111)-7×7 surface, the nucleation is observed to occur inside the unit cell of the superstructure. The formation and accretion of several generations of islands with nanosizes were observed. The periodic variations in the surface cell parameter of the Ge film were determined by RHEED during the formation of the wetting layer according to the 2D growth mode. It is argued that these variations are caused by elastic deformation of edges of two-dimensional nanoislands.
KeywordsScanning Tunneling Microscopy Image RHEED Pattern Atomistic Aspect Specular Beam Specular Intensity
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