Deposit Spot Patterns from Low-Index Planes of Metal Single Crystals in a New Theory of Cathode Sputtering

Abstract

The generation of the deposit spot patterns from low-index planes at lower and higher ion energy is explained by mechanical double and triple collisions of the perpendicularly incident ions with lower and upper surface atoms of the target plane. The effective collision spheres are assumed to be determined by the largest closed electronic shells of the ion and the target atom with radii smaller than the radii of the largest electronic orbits of these shells. A second factor has to be taken into account for the explanation of the shape and other features of the single spots of the patterns. This is the attenuating influence of the different electron densities in the paths of the ion within the lattice, because the largest closed electronic shells exceed the size of the collision spheres and produce the highest electron density in close-packed rows of the lattice. These two concepts are sufficient to explain the number and arrangements of the spots in the patterns of low-index planes, the specific shape of the single spots, the alterations of the spot patterns connected with higher ion energy or with accidental deviations of the prepared crystal plane from the ideal crystallographic plane, the deviation of the symmetry axis of the single spots in (110) fcc patterns from the diagonal direction of the unit area, and finally the different shape and size of the single spots in (111) spot patterns of silver and copper.