Kr incorporation in sputtered amorphous Si layers

Abstract

Amorphous Si layers were grown by krypton plasma sputter deposition at 310 °C. By pulsation of the substrate potential between 0 and 50 eV, the Kr concentration in the layers could be varied to a maximum of 5.5 at. %. A model which describes trapping of inert gas atoms in the sputtered layer in terms of implantation and trapping, diffusion, growth, resputtering, and gas sputtering is presented. High-resolution electron microscopy, electrode-probe (x-ray) microanalysis, positron annihilation, Raman spectroscopy, Mössbauer spectroscopy, and bending and hardness measurements were performed on the deposited layers. It turns out that the ion assisted growth leads to a strong reduction of open volume defects. The experiments point to the presence of very small Kr agglomerates. From the Mössbauer experiments a lower limit of 250 K for the Debye temperature of the Kr agglomerates is derived. Molecular-dynamic simulations from which the Debye temperatures of Kr mono-, di-, and trimers in amorphous Si can be derived are presented. The simulations indicate the presence of predominantly Kr monomers and dimers.