Interface formation in W/Si multilayers studied by Low Energy Ion Scattering

•Growth of W/Si multilayers studied with Low Energy Ion Scattering (LEIS).•W/Si interface asymmetry is not caused by ballistic effects.•W/Si interface thickness not directly affected by sputter gas choice (Ar or Kr).•Sputter gas choice (Ar or Kr) affects surface segregation of Si on W.•Segregated Si atoms are preferentially sputtered with backscattered Ar neutrals. We studied the formation of interfaces in W/Si multilayer structures deposited by magnetron sputtering. In vacuo Low Energy Ion Scattering Spectroscopy was used to determine the materials growth profile with a close to atomic resolution. For that purpose, bi-layer structures, W-on-Si and Si-on-W were grown, with Si being deposited using Ar as the sputter gas and W being deposited in either Ar or Kr. The measurements revealed strongly asymmetric interfaces, with W-on-Si being significantly broader than Si-on-W. However, no difference was found in the W-on-Si interface width depending on the sputter gas, Ar or Kr, used for W deposition, suggesting that it is not a ballistic effect of the backscattered gas ions that is responsible for the wider W-on-Si interface. However, strong surface segregation of Si atoms upon the deposition of W in Kr on Si was observed. Mechanisms responsible for the observed effects are discussed.