AN ION OPTICAL DECEL SYSTEM FOR OBLIQUE ANGULAR IMPACT OF LOW-ENERGY IONS ON TARGETS

A beam retardation system is presented for performing sputtering investigations with oblique angles of incidence of the ion beam. The system is designed for ion energies from 90 eV to 3 keV. For oblique ion impact it is necessary to have a field-free space in front of the target to avoid deflection of the beam in front of the tilted target due to an otherwise distorted electric field. A double-lens system yielding a parallel ion beam can meet this requirement if the lenses are movable in the beam direction. Such a system is described for a two-dimensional field. The system was tested with a tungsten ion beam in a tungsten self-sputtering investigation at an energy of 350 eV. For this ion-target combination a large angular dependence of the sputtering yield is expected. The results are compared with Monte Carlo calculations.