Interdiffusion at the Ge(100)/Sn and Ge(111)/Sn Interface.

Interdiffusion between an ultra-thin film of Sn and the GE (100)c2x4 and Ge(111)c2x8 surfaces under atomically clean conditions is investigated using Rutherford backscattering. Indiffusion is found only if the Sn coverage exceeds a certain critical coverage theta(c) ~~ 1.15X10(15) cm(-2) even at temperatures up to 700 K. This result implies that the diffusion coefficient is at least six orders of magnitude smaller than the literature bulk value for theta