Effects of surface treatments on photoelectric work function of silver-nickel alloys

Experimental results about silver-nickel alloys show a large dependence of obtained results with the preparation of contact surface. The EWF of the contact pastille made with silver alloys Ag-Ni varies with surface cleaning by vacuum outgassing cycles. For an unpolished contact, the EWF varies between 4.34 eV and 4.51 eV (the EWF of Nickel), after 7 cleaning cycles and cleaning time of 9 days. On the other hand, for a polished contact, the EWF varies between the EWF of the two components, namely from 4.26 eV for Ag to 4.51 eV for Ni, at room temperature, after 22 cleaning cycles and a cleaning time of 16 days. The error in determining EWF was ±0.03 eV. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results. In addition, a change of order of 0.1 eV was observed for silver alloys Ag-Ni (60/40) EWF after polishing. Afterwards, the microstructure of the contact surface was analyzed with scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS). The analyzes of the cathode surfaces before and after polishing enabled us to have evidence about the decrease of the electron work function for polished samples.