is then filled with a gas such as ar in the range of 1 u00d7 10 4 to about 10 u00d7 10 4 torr where 1 pascal 7 5 millitorr the target 10 and the substrate 12 are shown generally in the configuration shown in fig2 with the addition of a wire mesh grid 13 above target 10 which serves to separate the electrons in the beam 11 from the ions to prevent the electrons from reaching the surface of target 12 thereby creating an excessive current through the target 12 wire mesh 13 confines the electric field produced by voltage v t on the target 10 to a narrow region above the target surface where it is effective in accelerating sputtered ions before they are neutralized without this isolation it is virtually impossible to produce a positive bias on the target 10 under these conditions due to the large electron current drawn from the plasma in beam 11 which in this case is an ion beam composed of positive argon ions the source of ions is a standard kaufman ion source of the variety discussed in a chapter entitled 34 ion beam deposition 34 by j m e harper in a book entitled 34 thin film processes 34 edited.