Initial growth of titanium germanosilicide on Ge/Si(1 1 1)

The initial growth of titanium germanosilicide on Ge/Si(1 1 1) has been investigated and the role of a Ge buffer layer has been clarified. The surface morphologies and atomic structures were observed using AFM and STM. Ti films with 0.3–3.3 nm thicknesses were deposited at room temperature (RT) or high temperature (HT). In the reaction of a thin Ti (1.7 nm) with Si, only the island-like C49 structures were formed at 650°C annealing. When the Ge buffer layer of 4 ML (0.62 nm) was added, the strip-like C54 structures were also observed. The Ge buffer layer could lower the temperature of phase transformation from C49 to C54 structures. In the case of a ultra-thin Ti (0.55 nm), C54 structures were formed on Ge/Si(1 1 1) even at 550°C annealing. When 1.7 nm Ti was deposited on the HT Ge/Si substrate (650°C), nearly all structures formed were of C54. This indicates that the ultra-thin Ti evaporation and HT methods are effective at the initial growth. It was also found that C54 growth reflects the surface of the atomic structures.