EFFECT OF COMPOSITION GRADIENTS IN ALLOYS ON DIFFERENTIAL SPUTTER PARAMETERS

The influence of composition gradients in alloys on sputter characteri stics]las been studied theoretically on the basis of a model that is w ell established to describe collisional sputtering from a homogeneous material. General expressions have been derived relating the compositi on profile to angular and energy spectra of sputtered particles of the respective species. Surface depletion causes a narrowing of the angul ar distribution of the sputtered flux of a given species relative to t he case of a homogeneous target. A neutral angle (51.8 degrees in our specific model) is identified where the composition of the sputtered f lux is representative of the flux emitted into the halfspace, For ener gy spectra of sputtered atoms we find a flatter tail in case of surfac e depletion and a shift of the maximum which may be upward or downward dependent on emission angle. In particular we find a critical emissio n angle close to the neutral angle where the position of the maximum i s independent of the composition profile. (C) 1998 Elsevier Science B. V.