Growth of germanium nanoislands and nanowires on singular and vicinal Si(111) surfaces prior to the formation of a wetting layer

Abstract

The growth of germanium nanoislands and nanowires on singular and vicinal Si(111) surfaces is investigated by scanning tunneling microscopy (STM). It is shown that the formation of a Ge wetting layer on the Si(111) surface at germanium deposition rates of approximately 10−3 BL/min and epitaxial temperatures of 350–500°C occurs through the island or multilayer growth mechanism. This makes it possible to prepare arrays of Ge islands with a height of 3 BL and a density of 109–1012 cm−2. The growth of Ge nanowires with a constant height and a width dependent on the Ge coverage is observed on vicinal Si(111) surfaces. It is found that the surface diffusion coefficients of Ge adatoms on the Ge(5×5) surface are severalfold larger than those on the Si(7×7) surface. The Raman spectra of optical phonons on the Si(111) surface with Ge nanoislands 3 BL in height contain a number of lines associated with the quantization of the phonon spectrum along the [111] growth direction.