INTERFACE FORMATION IN SILICON BY CESIUM BOMBARDMENT

Experiment and computer simulation with the TRIDYN code are performed in order to study the contribution of collision processes to the inter face formation induced by 4-80 keV Cs ions incident on an amorphous si licon surface, The simulations show evidence for the fluence dependenc e of Cs range profiles and of the surface elevation (swelling) of the irradiated target, Range profiles become constant above some fluence w hose value depends on the incidence conditions. In the experiment, sat uration is traced by measuring the fluence dependence of the electron emission coefficient and is found to be of the same order as that foun d for simulated yields and ranges. Depth profiles are determined by TO F-spectroscopy in combination with layer-by-layer sputtering. The resu lts at 40 keV with a fluence above the saturation value are in qualita tive agreement with simulation, In contrast, strong deviations are fou nd at 4 keV which are attributed to surface Cs segregation.