Microscopic study of the surfactant‐assisted Si, Ge epitaxial growth
The Sb‐assisted Si, Ge epitaxial growth processes have been studied using high resolution photoemission. It is found that the initially ordered Sb monolayer on the Si(100) and Ge(100) surfaces occupies the epitaxial sites and fully saturates the surface dangling bonds. This results in a reduction of the surface energy. During the growth process, the Sb atoms and the deposited Si, Ge atoms change their positions. Sb atoms segregate to the growth front to form a new ordered layer while leaving the uniform epitaxial Si, Ge layer behind.
The interaction of Sb4 molecular beams with Si(100) surfaces: modulated-beam mass spectrometry and thermally stimulated desorption studies
Abstract Modulated-beam mass spectrometry and thermally-stimulated desorption measurements were used to show that Sb4 is dissociatively chemisorbed on clean Si(100) at all temperatures investigated, from 100 to 1025°C. For Si substrate temperatures Ts less than 600°C, desorption was only observed from precursor states corresponding to Sb4 molecules adsorbed on top of a dissociatively chemisorbed Sb layer. The Sb4 sticking probability s was nearly unity and independent of θSb for θSb ≲ 0.7 monolayers (ML) but decreased rapidly with increasing θSb above 0.7 ML to reach s = 0 at a saturation coverage of θSb = 1.0 ML (referenced to the surface site density of unreconstructed Si(100), 6.8 × 1014 cm−2). Above 600°C, the desorbing Sb4 flux decreased rapidly as the saturation coverage decreased and an increasing fraction of the impinging Sb4 flux was desorbed from dissociatively chemisorbed states as Sb monomers. Sb1 was the only desorbing species detected at Ts ≳ 800°C. The activation energy for Sb1 desorption was 2.40 ± 0.1 eV for θSb ≲ 0.5 ML and 2.33 ± 0.1 eV for θSb ≳ 0.5 ML as determined by thermally stimulated desorption, surface lifetime, and saturation coverage measurements. A simple model for Sb4/Si(100) interactions involving a mobile Sb4 precursor state and repulsive lateral interactions between chemisorbed Sb adatoms was used to calculate desorption rate kinetics and found to provide excellent agreement with the measured data.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.