Low temperature ion bombardment of Bi30Pd70-films - influence of the initial structure on the phase formation

Theoretical predictions make the BixPd1-x system a promising candidate for studying the possibility of amorphization by an enforced extension of the solubility into a metastable regime. By quench-condensation of Bi30Pd70, the existence of a previously unknown amorphous (a-) phase is proven, which above 520 K crystallizes into the monoclinic Bi2Pd5 phase. Ar+-irradiation of this crystalline phase at low temperatures leads back into the a-phase in accordance with a general amorphization rule. Experimentally, this behaviour is demonstrated by applying in situ resistance measurements and ex situ XRD. A surprising result is found for supersaturated Pd70Bi30 solid solutions, which can be prepared by exploiting interface reactions in Pd/Bi multilayers. Ion irradiation performed on these cubic metastable solid solutions under exactly the same conditions as above, result only in a segregation of the surplus Bi towards the equilibrium solubility limit. No irradiation induced amorphization can be obtained starting with a stable or metastable cubic solid solution