The formation of palladium silicide phases by implantation of Si ions into evaporated‐palladium films on two different substrates (Si and SiO2) has been investigated. The amount and phase of silicide formed depend on the implantation temperature, substrate type, and the penetration of the ions relative to the substrate depth. Provided the ions do not penetrate to the substrate, it is found that Pd2Si is formed for both types of substrate, even at 150 °K. When the ions just reach the Pd/substrate interface, the sample temperature and substrate type become important. For the SiO2substrate, the amorphous alloy Pd4Si forms at low temperatures. With the Si substrate Pd2Si forms under all conditions and there is a large incorporation of silicon from the substrate into the palladium, to an extent dependent on the temperature. This effect is explained in terms of radiation‐enhanced diffusion, possibly assisted by dynamic cascade mixing. In the SiO2substrate case, oxygen is thought to play an important role in determining the formation of phases.