SYNTHESIS OF A NOVEL PHASE IN A FE-CR ALLOY GROWN BY ION-ASSISTED CO-SPUTTER DEPOSITION

Fe-17.5Cr alloys have been grown on chemically polished silicon using co-sputter deposition with and without the use of 200 eV argon ion ass istance during deposition. Thin film glancing incidence X-ray analysis was then used to characterise the microstructure of the film, As expe cted for the co-sputter deposited film (grown without ion-assistance) the d-spacings corresponded closely to those of ferritic stainless ste el (Fe-18Cr) which has a bcc Fe structure. Surprisingly however, the f ilm deposited using ion assistance had a structure of a metastable chi -phase, similar to that of alpha-manganese. Normally large impurity sp ecies are considered essential for the stabilisation of this structure . The possible reasons for the formation of the chi-phase are discusse d in terms of the effects of the ion assistance on film growth.