Mechanisms of ion beam mixing in metals and semiconductors

Ion beam mixing was investigated in crystalline and amorphous semiconductors and metals using molecular dynamics simulations. The magnitude of mixing in an amorphous element compared to its crystalline counterpart was found to be larger by a factor of 2 or more. Mixing in semiconductors was found to be significantly larger than in a face-centered-cubic (fcc) metal of corresponding mass and atomic density. The difference in mixing between amorphous and crystalline materials is attributed to local relaxation mechanisms occurring during the cooling down phase of the cascade. Comparison of mixing in semiconductors and metals shows that short range structural order also has a significant influence on mixing. The mixing results in fee metals indicate that the role of the electron-phonon coupling in the evolution of collision cascades may be less significant than previously thought.