Measurements of secondary electrons emitted from conductive substrates under high-current metal ion bombardment

The yield of secondary electrons induced by primary ion impact is measured for conditions relevant to metal plasma immersion ion implantation. A vacuu m are ion source provided metal ions in the energy range 5-175 keV. The tar get materials were placed in a Faraday cup, and the secondary electron yiel ds were determined by measuring the current of the Faraday cup with and wit hout electron-suppressing magnetic field. By using a time of flight method, yields for individual ion charge states could be determined. The yields fo und depend on the ion species, their energy, and the target material. They are in the range 1-10 electrons per ion for the conditions investigated. It was found that the yields are almost independent of the ion charge state a nd increase with increasing ion energy. (C) 2001 Elsevier Science B.V. All rights reserved.