Formation of Ge-Sn nanodots on Si(100) surfaces by molecular beam epitaxy

The surface morphology of Ge(0.96)Sn(0.04)/Si(100) heterostructures grown at temperatures from 250 to 450°C by atomic force microscopy (AFM) and scanning tunnel microscopy (STM) ex situ has been studied. The statistical data for the density of Ge(0.96)Sn(0.04 )nanodots (ND) depending on their lateral size have been obtained. Maximum density of ND (6 × 10(11 )cm(-2)) with the average lateral size of 7 nm can be obtained at 250°C. Relying on the reflection of high energy electron diffraction, AFM, and STM, it is concluded that molecular beam growth of Ge(1-x)Sn(x )heterostructures with the small concentrations of Sn in the range of substrate temperatures from 250 to 450°C follows the Stranski-Krastanow mechanism. Based on the technique of recording diffractometry of high energy electrons during the process of epitaxy, the wetting layer thickness of Ge(0.96)Sn(0.04 )films is found to depend on the temperature of the substrate.