Wetting of nickel films of variable thickness by island lead condensates

The wetting of nickel films deposited on NaCl (100), Si (111), and GaAs (111) single crystals by island lead condensates has been studied. It has been shown that with an increase of the Ni film thickness the contact angle changes from the value corresponding to the wetting of a clean single-crystal substrate to the wetting of the bulk nickel one. Complete substrates properties damping was achieved at nickel thicknesses of about 40, 90 and 20 nm for NaCl, Si, and GaAs, respectively. The contact angle θ change has been explained by the heterogeneity of the wettable surface. It seems to be that such heterogeneity is a result of both: the chemical interaction of the nickel film with silicon and gallium arsenide, and the nickel dissolution in liquid lead.