The effect of ion implantation and solute atoms on the interdiffusion in amorphous Si/Ge multilayers

Amorphous Si/amorphous Ge multilayers were prepared by ion beam sputtering. Silicon, boron, gold, or oxygen atoms were introduced into the Si/Ge multilayers by ion implantation or during the sputtering deposition. Diffusion or ion mixing lengths were determined by measuring the decrease in the intensity of the first-order x-ray diffraction peak resulting from the composition modulation. Annealing of Si-implanted samples showed that after relaxation the diffusivity appeared unaffected by the implantation process. Annealing of the multilayers containing B or Au showed that the interdiffusion of Si and Ge in their amorphous phase can be enhanced by doping, while O implantation showed no effect. The enhancement factor is independent of the degree of structural relaxation, as observed by the decrease of diffusivity with annealing time, of the amorphous phase. A model is proposed that describes this behavior in terms of electronic effects, introduced by dopants, on the pre-existing structure defects governing interdiffusion.