Self-Diffusion of Ge in Amorphous Ge Si_1- Films Studied In Situ by Neutron Reflectometry

Ge Si_1- alloys are gaining renewed interest for many applications in electronics and optics, especially for miniaturized devices showing quantum size effects. Point defects and atomic diffusion play a crucial role in miniaturized and metastable systems. In the present work, Ge self-diffusion in sputter deposited amorphous Ge Si_1- alloys is studied in situ as a function of Ge content x = 0.13, 0.43, 0.8, and 1.0 by neutron reflectometry. The determined Ge self-diffusivities obey the Arrhenius law in the investigated temperature ranges. The higher the Ge content x, the higher the Ge self-diffusivity at the same temperature. The activation enthalpy decreases with x from 4.4 eV for self-diffusion in pure silicon films to about 2 eV self-diffusion in Ge_0.8Si_0.2 and Ge. The decrease of the activation enthalpy for amorphous Ge Si_1- is similar to the case of crystalline Ge Si_1- . Possible explanations are discussed.