Alloy films work function measurements

It has indeed been found (83a) that the work function of Ag-Pd alloy films equilibrated at 300°C only changes from 4.38 eV at pure silver to 4.50 eV at 86% Pd (increasing to 5.22 at pure Pd). It was proposed (83a) that this work function pattern is a consequence of surface enrichment by silver and so confirmation of the theory awaits further work function measurements on alloy surfaces for which compositions have been determined by, say, Auger electron spectroscopy. 

Further progress in the study of the Cu-Ni system awaited the preparation and careful characterization of alloy films of known bulk and surface composition. The essential step was taken by Sachtler and his co-workers 28, 88, 114) who prepared Cu-Ni alloy films by successive evaporation of the component metals in UHV. After evaporation the films were homogenized by heating in vacuum at 200°C. The bulk composition of the alloys was derived from X-ray diffraction, and the photoelectric work function of the films was also measured. A thermodynamic analysis, summarized by Fig. 13, indicated that alloy films sintered at 200°C should consist, at equilibrium, of two phases, viz., phase I containing 80% Cu and phase II containing 2% Cu. Evidence was presented that alloys within the... 

Fig. 30. Work function of Pt-Au alloy films prepared by simultaneous deposition at — 196°C measured at room temperature ( ) and after sintering at 300°C (O) (41).

Atomic force microscopy (AFM) and electrochemical atomic force microscopy (ECAFM) have proven usefiil for the study of nucleation and growth of electrodeposited CP films on A1 alloy [59]. AFM was used to study adhesion between polypyrrole and mild steel [60], whereas electric force microscopy (EFM) has been used to study local variations in the surface potential (work function) of CP films [61]. AFM with a conductive tip permits a nanoscale AC impedance measurement of polymer and electrolyte interfaces, permitting differentiation between highly conductive amorphous regions and less-conductive crystalline regions of the CP film [62]. 

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