THE OBSERVATION OF A THRESHOLD IN THE DE-ALLOYING OF SPUTTER-DEPOSITED PTXAL1-X ALLOY THIN-FILMS

Platinum-aluminium alloys of various compositions were synthesised by using DC co-sputter deposition and then immersed in 4 M NaOH under ope n-circuit conditions. The selective dissolution of aluminium was studi ed with Rutherford backscattering spectroscopy (RBS) and secondary neu tral mass spectrometry (SNMS). A threshold at Pt0.4Al0.6 was observed. For platinum contents above 40 at%, RBS analysis showed that little a luminium dissolution occurs. There was also evidence for the formation of a thin (less than 5 nm thick) platinum-rich surface film. At plati num contents lower than 40 at% profuse aluminium dissolution occurred. RES and SNMS analyses suggested that dissolution occurs throughout th e him. (C) 1997 Elsevier Science Ltd.