Kinetic control of dome cluster composition by varying Ge deposition rate

The mean size of dome clusters grown by molecular beam epitaxy of pure Ge onto Si(100) at substrate temperatures, T, of 550°C und 650°C is deposition rate dependent. For samples with nominal Ge coverages near 8 ML (1 ML = 6.78 × 10¹⁴ atoms/cm²) and deposition rates between 1.4 and 17.5 ML/min, higher deposition rates decreased the mean dome diameter und increased the dome areal density. Additionally, the critical volume for the pyramid-to-dome transition decreases with increasing deposition rate for islands grown between T= 550°C and 650°C. By this measure, the Ge content of the dome clusters rises with increasing deposition rate. Quantitative, nm-resolved electron energy loss spectroscopy (EELS) measurements taken in a scanning transmission electron microscope confirm these results. For domes grown at T = 650°C with rates of 1.4 ML/min and 17.5 ML/min, EELS indicates 59% and 70% Ge compositions, respectively. These results show that dome cluster composition may be kinetically controlled by varying the Ge deposition rate.