Growth modes of Ag deposited on Si(111) with simultaneous low energy ion bombardment

Abstract

The influence of simultaneous low-energy argon ion bombardment on the nucleation and growth of sputter-deposited silver on p-doped Si(111) under ultra-high vacuum conditions has been investigated using Auger electron spectroscopy in conjunction with proton-induced X-ray emission (PIXE). Argon ion energies used were 0.5, 1.0, and 1.5 keV with the ratio of ion arrival rate to silver atom arrival rate ranging from 0.14 to 0.5. The intensities of the SiLVV and AgLVV Auger transitions were measured as a function of total deposition time. Proton-induced X-ray emission was used to measure the thickness (areal density) of the deposited silver as a function of deposition time, allowing the growth mode of the film to be determined by plotting the ratio of AgLVV/SiLVV Auger intensities as a function of film thickness. For the case of deposition without ion beam activation, results were consistent with a Stranski-Krastanov, or layer-plus-island growth mode. At elevated temperature (420 ° C), the same growth mode was observed, but with substantially lower fractional silver island coverage. For simultaneous ion bombardment with 0.5 and 1.0 keV Ar +, a change to layer-by-layer growth was observed to occur at 4.5 and 6 equivalent monolayers, respectively, for ion-to-atom arrival ratios greater than 0.34. This phenomenon is likely due to sputter redeposition and ion enhanced nucleation site formation.