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.
High-resolution Si 2p core-level photoemission spectroscopy on Sb-terminated Si(100) surfaces: evidence for a strong interfacial component
Abstract High-resolution core level spectroscopy using a third-generation synchrotron light source has been used to characterize the Sb-terminated Si(100) surface. On the Sb-terminated surfaces, all the components of the Si 2p core level related to the clean surface have disappeared, and one new Sb-induced component could be identified at a binding energy +0.20±0.01 eV with respect to the bulk peak. On the Sb-1×1 reconstruction, we found a very narrow bulk component [Gaussian full-width half maximum (FWHM) of 150 meV and Lorentzian FWHM of 85 meV], indicative of an ideal bulk termination. On the Sb-2×1 reconstruction, a broader bulk component is needed to fit the Si 2p line (Gaussian FWHM of 180 meV), indicative of some reorganization of the topmost silicon atoms following Sb–Sb dimers formation. A small component, probably due to local disorder, is present on the high-kinetic-energy side for both surfaces at −0.2 eV. The Sb 4d core-level spectrum is well represented by one doublet, thus suggesting that each Sb atom is adsorbed in a unique environment, i.e. there is no multisite adsorption.
Comparison of diffusion theory adsorption and desorption rate constants with experimental lifetimes
Stimulated by the success of the diffusion theory for nonequilibrium gas phase recombination and dissociation, an analogous theory for nonequilibrium adsorption and desorption has been formulated. Experimental adsorption and desorption lifetimes are compared with the resulting steady state adsorption, and desorption rate constants. The goal of this comparison is to obtain gas‐surface potential parameters for each adatom‐substrate species combination for which data is available. The adatom energy distribution is obtained from a diffusion equation approximation to the governing master equation. The energy transition kernel is developed using an harmonic potential in the soft‐cube model for the gas‐surface collision. It is found that the pre‐exponential factor in the desorption lifetime may be represented by a power series in the nondimensional potential well depth, δ = D / kTg . Gas surface potential parameters are derived for cadmium,gallium, titanium, cesium, silver, and rubidium on tungsten by comparison with desorption lifetimes. Adsorption lifetimes are predicted for these species. Good agreement is obtained with experimental measurement of the adsorption lifetime of xenon on tungsten.Adsorption and desorption lifetimes for xenon, krypton, and argon on tungsten; xenon, argon, and neon on gold; xenon, krypton, and argon on platinum; and xenon, krypton, and argon on silver are predicted over a wide range of gas and surface temperatures for comparison with future experiments.