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.