Crystallization of amorphous Si_0.5Ge_0.5 films studied by means of in-situ X-ray diffraction and in-situ transmission electron microscopy

The effect of B and P doping on the crystallization kinetics of amorphous Si_0.5Ge_0.5films was studied by means of in-situ X-ray diffraction (XRD) and in- situ transmission electron microscopy (TEM). Amorphous Si_0.5Ge_0.5 films, doped and undoped, were deposited by the molecular beam method on SiO₂/Si(001) substrates and annealed at temperatures between 500 and 600°C. The crystalline fraction in the films was evaluated by following the intensity of the (220) reflection, obtained by in-situ XRD, as a function of time. It is demonstrated that the crystallization kinetics follow the Avrami formalism. The overall activation energy of crystallization was found to be 3.49eV for P-doped (10²⁰cm^-3) Si_0.5Ge_0.5films. In addition, crystallization parameters such as the incubation time, the nucléation rate and the grain growth rate were determined directly by in-situ TEM. The activation energies for grain growth and for the overall transformation were found to be 2.7 and 2.4 eV respectively for undoped Si_0.5Ge_0.5films. The films which were highly doped with B and P showed higher crystallization rate than the undoped films did.