Ion-induced photon spectroscopy of insulators and application to in-situ diagnostics of nanoparticle formation processes

Ion-induced photon emission under heavy-ion bombardment has been studied over an energy range from near-infrared to vacuum-ultraviolet. Time-resolved optical devices with fast-response CCD cameras detected photons from a-SiO₂ under implantation with negative Cu ions of 60 keV, up to a dose rate of 100 μA/cm². The ion-induced photon spectra consisted of sharp line spectra due to isolated atoms of Si, Cu and a broad band of visible light. The line spectra resulted from an ion-induced glow above the surface and indicated pronounced outward transport of Cu atoms to the vacuum. Intensity of the line spectra and the broad band varied non-linearly with dose and dose rate. The in-situ spectroscopy provided diagnostic information of surface- and intra-solid processes associated with nanoparticle formation at high dose rates. The Cu sublimation reflected from presence of a Cu-depleted zone beneath the surface, which is one of the important factors to form a two-dimensional arrangement of nanoparticles.