THE ANISOTROPY OF MOMENTUM DISTRIBUTIONS IN ATOMIC COLLISION CASCADES
The distribution of particle momentum directions in atomic collision cascades are studied by means of computer simulation with the MARLOWE program. In contrast with the random model, the atomic collision cascade generation in single crystals is found to be highly anisotropic at every stage of the energy dissipation. It is entirely governed by the lattice crystallography. In addition to the well-known one-dimensional focusing effects, two-dimensional transient focusing is found to play an important role in the cascade development. Unstable one-dimensional trajectory focusing also provides a large contribution to the momentum direction distributions at various stages of the cascade generation. Large thermal displacements of lattice atoms are not found to randomize the cascades. They may, however, induce anisotropy characteristics in momentum direction distributions different from those calculated for a static lattice. The anisotropy found in experimental and simulated angular distributions of sputtered particles is directly related to the anisotropy of the cascade development and is only poorly described by earlier interpretations.
Bibliographic Reference: REPORT IPP-9/65, 1988, AVAILABILITY: MAX-PLANCK-INSTITUT, MUENCHEN, D
Record Number: 1989126099800 / Last updated on: 1989-05-01
Available languages: en