In situ optical spectroscopy during deposition of Ag:Si 3N 4 nanocomposite films by magnetron sputtering

Abstract

In situ and real time surface differential reflectance (SDR) spectroscopy is employed to study the growth of metallic Ag and/or dielectric Si 3N 4 films during deposition by magnetron sputtering. The measurements during Si 3N 4 sputtering allow determining both the refractive index and the deposition rate. During Ag sputtering, the SDR presents a maximum in the visible range, typical of a surface plasmon resonance (SPR) indicating the 3D growth of silver nanoclusters. After a certain deposition thickness, the SDR change corresponds to a continuous layer growth and allows determining the Ag deposition rate. During Ag/Si 3N 4 alternate deposition, the SDR spectroscopy enables to follow the SPR modifications (position, amplitude and width) not only during the formation of the Ag nanoclusters but also during their capping by a Si 3N 4 matrix and during intermediate steps (holding time after the silver sputtering, Si 3N 4 target ignition and pre-sputtering before the Si 3N 4 deposition) where significant changes are detected. It suggests possible nanocluster reshaping or physicochemical processes occurring at the nanocluster interface during the different steps.