The formation of iron silicides on (0 0 1)Si and the effects of BF2+-, As+- and P+-implantation on the phase transformation have been investigated. All implantation species were found to enhance the growth of light-emitting beta-FeSi2 with the effects of P+- and As+-implantation most and least pronounced, respectively. The transformation temperature from FeSi to beta-FeSi2 was lowered from 700 to 600 degreesC and the formation of beta-FeSi2 was completed at 700 degreesC. The transformation of beta-FeSi2 from FeSi was found to be by clustered growth. Grain boundaries were observed to be decorated with As atoms in the As+-implanted samples annealed at 700-800 degreesC. The As-rich grain boundaries disappeared after 900 degreesC annealing.