Autoelectronic emission and charge relaxation of thorium ions implanted into a thin-film silicon oxide matrix

Abstract

An ensemble of thorium-229 ions embedded by pulsed laser implantation into a matrix of a broadband dielectric-silicon oxide is studied. The results of the experimental investigation of thorium ions’ lifetime as charged components of the Th+/SiO2/Si system formed immediately after laser implantation are presented. The modelled theoretical description takes into account the instantaneous charging of the surface via laser implantation followed by charge relaxation due to the effect of autoelectronic emission that leads to time dependent partial neutralization of the surface charge by tunneling electrons. It was found that the lifetime of Th+ ions on the SiO2 surface can exceed 10 s, which would be an attractive opportunity for studying the nuclear low-lying isomeric transition in the thorium-229 isotope.