ENERGY-TRANSFER FROM NOBLE-GAS IONS TO SURFACES - COLLISIONS WITH CARBON, SILICON, COPPER, SILVER, AND GOLD IN THE RANGE 100-4000 EV

The energy deposited into carbon, silicon, copper, silver, and gold surfaces by He+, Ar+, and Xe+ ions impinging with kinetic energy in the range 100-4000 eV has been measured. These studies employed a highly sensitive calorimeter together with a modified physical electronics instrument ion gun. Pulses of ions from the gun were directed at the film that had been evaporated directly onto the pyroelectric material. A voltage proportional to the energy deposited is developed across the material and sensed with a lock-in detector. Xe+ deposits more than 95% of its energy between 500 and 4000 eV for all materials. The other ions deposit at least 80% of their energy in this range. The dependence of energy deposition upon ion and substrate mass and ion energy is about that expected from calculations and physical principles. The energy reflection from surfaces is also investigated by computer simulation using the TRIM.SP program. The experimental trends are semiquantitatively reproduced by the simulation, but there are some quantitative differences in the absolute results. As would be expected from previous calculations, the energy-reflection coefficients do not appear to scale with the ratio of target mass to ion mass or with reduced energy. The implication of these results for the understanding of collisional processes at solid surfaces will be discussed.