Establishment of Charging Free and Non-Scatter Implantation Technology for Micro Powders by Using Negative-Ion Beam

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1.Elucidation of Particle-Scattering Phenomenon and Threshold Charging VoltageScattering of powders during conventional positive-ion implantation without any charge compensation results from a high charging voltage. Taking account of forces acting on one particle in the top layr : Coulomb repulsive force and attractive forces to other particles in the layr just below, such as gravity and van der Waals force, the threshold charging voltage for scattering was derived for a stationary state and a vibrated state. This relation was confirmed by experiments. Thus, we have clarified the mechanism of particle scattering.2.Development of Negative-Ion Implanter for Powders with an Agitator and Non-ScatteringWe constructed a negative-ion implantation for micro-powders as equipped with ion beam bending deflector and an agitator of electromagnetic vibrator at a frequency of 120 Hz. With this implanter, various negative ions were implanted into powders at 70 keV.No scattering was observed. The negat … More ive-ion implantation is found a nonscattering implantation method for powders.3.Evaluation of Charging Surface Potential of Insulators at Negative-Ion ImplantationWe measured surface potentials of several kinds of insulators by secondary electron energy analysis. The surface potential during negative-ion implantation was only several volts negative much less than threshold voltage. Therefore, scattering is considered to not result in negative-ion implantation.4.Establishment of Agitation Method by Vibration for Treatment of Whole Surface of Powder-ParticlesFor agitation by vibration, required conditions of frequency and amplitude were theoretically driven. The conditions were confirmed by vibration experiments. For evaluation of uniformity, copper negative ions were implanted into glass beads. From contents of copper atoms in a bead by XPS,the implantation under the vibration was found to make treatment of whole surface with good uniformity.Thus, we developed a negative-ion implanterfor powders and established negative-ion implantation into powders as a charging free and non-scattering ion implantation method with a good uniformity. Less