Influence of Charging Conditions on Field Ion Emission From Dust Grains

This paper deals with field ion emission (FIE) of spherical gold grains of micrometer sizes. We have analyzed the discharging characteristics measured under different conditions on one gold grain and suggested that the process limiting the discharging current is probably a diffusion of primary ions toward the grain surface. In order to confirm this hypothesis, we concentrated on the influence of the charging conditions (ion beam energy, ion species) on the discharging current. The investigations show that the ion field emission is a very complex process in which the charging conditions can change the discharging rate by an order of magnitude for a given electric field. We found that the total dose of the ions impacting the dust grain is an important parameter of the FIE. Our possible explanation is based on the implantation of the charging ions and their diffusion toward the surface of the dust grain