Nucleation and Growth Mechanisms in Cu-Co Films

AGUIRRE MARIA DEL CARMEN; S.URRETA

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2016 vol. 120 p. 22142 - 22154

1932-7447

Nucleation and growth mechanisms in Co, Cu,and CoxCu100−x single films, and in CoxCu100−x/Cu bilayers,electrodeposited on Cu70Zn30 brass substrates, are studied bythe constant potential technique. The recorded current−timetransients (CTTs) are rather complex, and they extend forlong times. Co, Cu, and CoxCu100−x alloys electrocrystallizeonto brass, undergoing a process with more than a singlemaximum during the CTTs, as if two or more consecutivenucleation steps were present. The first stage of electrocrystallizationin Co and CoxCu100−x films involves 3Dinstantaneous nucleation, but then, at long times, a progressivenucleation regime predominates. CTTs in Cu/brass and in Cu/CoxCu100−x/brass bilayers are well fitted by a 2DP progressive nucleation process at the initial stage, while for longer growingtimes a transition to a 3DP regime is observed, in which film growth becomes controlled by adatoms incorporation to the lattice.Film morphologies observed by SEM are consistent with these growth mechanisms. XRD results indicate that pure Co layers arehcp phase, while Cu and Cu−Co layers have an fcc lattice. Films are soft ferromagnetic, with an ?in-plane? magnetization easyaxis; there is evidence of crystallographic texture, which should be responsible for the higher coercivity observed in the ?out-ofplane?configuration, with the applied field perpendicular to the film plane.