31 research outputs found
The role of step edge diffusion in epitaxial crystal growth
The role of step edge diffusion (SED) in epitaxial growth is investigated. To
this end we revisit and extend a recently introduced simple cubic
solid-on-solid model, which exhibits the formation and coarsening of pyramid or
mound like structures. By comparing the limiting cases of absent, very fast
(significant), and slow SED we demonstrate how the details of this process
control both the shape of the emerging structures as well as the scaling
behavior. We find a sharp transition from significant SED to intermediate
values of SED, and a continuous one for vanishing SED. We argue that one should
be able to control these features of the surface in experiments by variation of
the flux and substrate temperature.Comment: revised and enlarged version 12 pages, 5 figures, to appear in
Surface Scienc
Unconventional MBE Strategies from Computer Simulations for Optimized Growth Conditions
We investigate the influence of step edge diffusion (SED) and desorption on
Molecular Beam Epitaxy (MBE) using kinetic Monte-Carlo simulations of the
solid-on-solid (SOS) model. Based on these investigations we propose two
strategies to optimize MBE growth. The strategies are applicable in different
growth regimes: During layer-by-layer growth one can exploit the presence of
desorption in order to achieve smooth surfaces. By additional short high flux
pulses of particles one can increase the growth rate and assist layer-by-layer
growth. If, however, mounds are formed (non-layer-by-layer growth) the SED can
be used to control size and shape of the three-dimensional structures. By
controlled reduction of the flux with time we achieve a fast coarsening
together with smooth step edges.Comment: 19 pages, 7 figures, submitted to Phys. Rev.
Molecular beam epitaxial growth and characterization of (100) HgSe on GaAs
In this paper, we present results on the first MBE growth of HgSe. The influence of the GaAs substrate temperature as well as the Hg and Se fluxes on the growth and the electrical properties has been investigated. It has been found that the growth rate is very low at substrate temperatures above 120°C. At 120°C and at lower temperatures, the growth rate is appreciably higher. The sticking coefficient of Se seems to depend inversely on the Hg/Se flux ratio. Epitaxial growth could be maintained at 70°C with Hg/Se flux ratios between lOO and ISO, and at 160°C between 280 and 450. The electron mobilities of these HgSe epilayers at room temperature decrease from a maximum value of 8.2 x 10^3 cm2 /V' s with increasing electron concentration. The concentration was found to be between 6xlO^17 and 1.6x10^19 cm- 3 at room temperature. Rocking curves from X-ray diffraction measurements of the better epilayers have a full width at half maximum of 5S0 arc sec