A novel procedure for measuring the absolute current density profile of a focused gallium-ion beam

A simple and sensitive method has been developed for measuring the absolute current density profile of a focused gallium-ion beam down to six orders of magnitude below its peak intensity. This method exploits both physical sputtering and a chemical etch-stop mechanism that occurs on Si(100) substrates after Ga-ion implantation. Sputtering creates craters on the substrate while the ion implanted area becomes insoluble in aqueous NaOH. This etch-stop layer can be used as negative resistance for creating hillocks on the substrate. By measuring the topographs of sputtered craters and etched hillocks using atomic force microscopy, the absolute current density profile of the focused ion beam is deduced. (C) 1996 American Institute of Physics.