The depth profile of a Co (300 A˚)/Ti (50 A˚) bilayer on Si(100) is studied by nondestructive refracted x‐ray fluorescence before and after annealing. Following annealing, the angular distribution of the x‐ray fluorescence indicates an inversion of the Co and Ti layers and the formation of CoSi2. These were confirmed by cross‐section transmission electron microscopy and x‐ray nanoprobe measurements. This success suggests that refracted x‐ray fluorescence, which can be used as aninsituprobe, may be ideally suited for analysis of thin‐film reactions and interdiffusion. ©1995 American Institute of Physics.