ENERGY AND ANGULAR-DISTRIBUTIONS OF SPUTTERED PARTICLES

A review is presented on energy and angular distributions of atomic, molecular and cluster particles sputtered from solid surfaces under ion bombardment. The review is preferentially focused on experimental results and the corresponding experimental methods; theories about sputtering phenomena are used more as guide-lines for discussion and comparison. The four main areas considered are sputtering of (1) metals, (2) alkali halides, (3) frozen gases, and sputtering by (4) MeV ion impact on insulators. Analysis of the experimental data on energy and angular distributions has revealed a large variety of sputtering modes such as elastic and inelastic collisional sputtering, ion-induced thermal evaporation, ejection of excited atoms, sputtering due to exciton decay, formation of clusters or ejection of grains, sputtering by shock waves and formation of craters associated with an explosive gas flow. The comparison of experimental and theoretical data shows that the theory of linear collision cascades is a good basis for an understanding of the elastic sputtering processes. Also, recent computer simulations of sputtering give valuable insight into collisional processes. The situation is more complex when electronic excitation is the driving interaction of the sputtering process. In this case, depending on the type of target material and the energy loss of the primary ions, a large number of theoretical attempts have been made to describe individual phenomena attributed to electronic sputtering.