Initial growth stages of Si–Ge–Sn ternary alloys grown on Si (100) by low-temperature molecular-beam epitaxy

Temperature dependence of the critical thickness of the transition from two-dimensional to threedimensional growth of the Ge$_{1-5x}$Si$_{4x}$Sn$_x$ films grown on Si (100) by molecular-beam epitaxy in the temperature range 150–450$^\circ$C has been experimentally determined. This dependence is nonmonotonic and is similar to that of the critical thickness for the transition from two-dimensional to three-dimensional growth in the case of the deposition of pure Ge on Si (100) and is caused by a change in the mechanism of two-dimensional growth. Data on the average size and the density of islands, and the ratio between the height of the islands and their lateral size are obtained by the methods of atomic force microscopy and scanning tunneling microscopy. As the growth temperature is increased from 200 to 400$^\circ$C, the average size of the nanoislands increases from 4.7 to 23.6 nm.