Self-propagating explosive reactions can occur in multilayer thin films. Explosive silicidation in nickel/amorphous-silicon multilayer thin films has been investigated using a combination of high-speed photography, high-speed temperature measurements, plan-view transmission electron microscopy, and thin film x-ray diffraction. The multilayer films had an atomic concentration ratio of 2 Ni atoms to 1 Si atom. The silicide phase formed by explosive silicidation was Ni2 Si. This was the same phase formed by conventional thermal annealing of the multilayer thin film. The temperature of the explosive reaction front was measured to be approximately 1565 K. The reaction-front velocity was found to vary from 22 to 27 m/s and to be at most weakly dependent on the modulation period and the total film thickness. The resulting Ni2 Si grain structure formed by explosive silicidation is less defective than Ni 2 Si formed by conventional thermal annealing. This was attributed to the higher reaction temperatures and the shorter reaction times of explosively formed Ni2 Si as compared to Ni2 Si formed via conventional annealing.