J. K. Dash, A. Rath, R. R. Juluri, P. V. Satyam
The morphological evolution and the effect of growth temperature on size, orientation and composition of molecular beam epitaxy grown Ge-Si islands on Si(5 5 12) surfaces have been investigated in the temperature range from room temperature (RT) to 800$^\circ$C with two modes of substrate heating i.e. by radiative heating (RH) and direct current heating (DH). The post-growth characterization was carried out \emph{ex-situ} by scanning electron microscopy(SEM), cross-sectional transmission electron microscopy(X-TEM) and Rutherford Backscattering Spectrometry(RBS). In the RH case, we found spherical island structures at 600$^\circ$C with a bimodal distribution, which upon increasing temperature, structures got faceted at 700$^\circ$C. At 800$^\circ$C thick ($\sim$ 122nm) dome like structures are formed having shallow facets, steep facets and a top facet. While in the case of DC heating, after the optimum critical temperature 600$^\circ$C, well aligned trapezoidal Si$_{1-x}$Ge$_x$ structures with a graded composition starts forming along the step edges.Interestingly, these aligned structures have been found form only around 600$^\circ$C, neither at low temperature nor at higher temperatures.
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http://arxiv.org/abs/1205.6039
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