Interactions in the Co/Si thin-film system. II. Diffusion-marker experiments

Abstract

The Kirkendall effect in thin‐film Co/Si couples is investigated by He backscattering using diffusion markers. The couples contain the compounds Co₂Si and CoSi. The markers used are Xe implanted into Si, C, or Co₂Si and a discontinuous W film between Si and Co. In the case of Xe implantation into Co, the experiments can be explained by dragging of Xe bubbles by the moving Co/Co₂Si phase boundary. Xe implanted into Si is located at the Si/CoSi interface after the reaction and W is found at the Co/Co₂Si interface after the reaction. The same applies to Xe implanted through Co into Co₂Si. The results are evidence for predominant Co diffusion in Co₂Si growth and Si diffusion in CoSi growth. Grain‐size measurements suggest that grain‐boundary diffusion plays a role in the growth of the silicide layers. The results of a Xe implantation into Co₂Si without Co suggests that at the Co₂Si/CoSi interface both Si and Co diffusion currents flow.