Self-Diffusion of Ge in Amorphous GexSi1–x Films Studied In Situ by Neutron Reflectometry

GexSi1–x 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 GexSi1–x 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 Ge0.8Si0.2 and Ge. The decrease of the activation enthalpy for amorphous GexSi1–x is similar to the case of crystalline GexSi1–x. Possible explanations are discussed.