STM study of step graded Si_(1-x)Ge_x/Si(001) buffers

摘要

We report on the surface structure of step graded Si_(1-x)Ge_x/Si(001) buffers, as obtained by scanning tunneling microscopy (STM). The samples in this study were grown by means of rf magnetron sputter epitaxy (MSE). The study was performed by varying two essential growth parameters: the substrate temperature and the final Ge concentration x_f of the buffer. The emergence of the typical cross-hatched surface was monitored by investigating the surface at x_f = 0.15, 0.20 and 0.30. The influence of the growth temperature was studied in the range between 370 and 570 deg C. Even at the lowest temperatures, the strain was found to be partially relieved as evidenced by the formation of a cross-hatch.