Chemical enhancement of secondary ion emission from Cd ion bombarded Mo, Ti, Al and Cu surfaces

The variation of secondary ion intensity with target current was found to be linear and parabolic for low and medium current densities, respectively. A semi-empirical formula was proposed earlier to correlate these two effects. With further increase of target current density, it is found that the secondary ion yield varies approximately as cube of the primary current density. This enhanced ion emission has been attributed to the chemical enhancement effect caused by reactive ion bombardment. The semi-empirical formula has accordingly been modified in order to take into consideration the above effect. The combinations Cd⁺-Mo, Cd⁺-Ti, Cd⁺-Al and Cd⁺-Cu have been studied and the results are explained in terms of the modified semi-empirical formula. Our observations have further been supported by ion yield versus bombarding energy studies for the combinations: Cd⁺-Mg, Cd⁺-Ti and Cd⁺-Zr.