Self-organization during Si1−yCy alloy layer growth on Si(001) using homogeneous coevaporation

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Abstract
We show that the formation of self-organized pseudosuperlattices during homogeneous epitaxialgrowth of Si 1−y C y on Si(001) is a fundamental phenomenon not limited to special growth techniques. For samples grown at higher temperatures, and therefore, with higher concentration of nonsubstitutional carbon, we find contrast variations in cross-sectional transmission electron microscopy, roughly periodic in the growth direction in epitaxial Si 1−y C y alloy layers. The periodicity is a monotonic function of growth temperature and growth rate. Although the final explanation of this phenomenon remains an open question, we are able to rule out several possible effects. These structures do not reflect a modulation in the substitutional C content, the formation of the C-rich Si n C phases, or the segregation of nonsubstitutional C-containing defect complexes up to a certain saturation level. Rather, we show that the layers formed during the different growth processes contain different amounts of carbon. There is no critical size of the C-containing defect complexes independent of growth conditions that could lead to the formation of the observed structures. The variation of the periodicity with growth rate and temperature is similar to surface diffusion processes with an activation energy of 0.94±0.04 eV, close to the value for Si adatom diffusion on a Si(001) surface.