The work function of the Cu-deposited Ti emitter

We have measured the field-emission characteristics of the Cu-deposited Ti emitter and studied the change in the work function due to the Cu deposition. The emitter work function was obtained from the slope of the Fowler–Nordheim plot. Upon depositing Cu on Ti, we found that the work function increases by 0.1–0.2 eV. Annealing the deposited emitter gives a larger increase in the work function. We could not observe the reduction in work function predicted by Yoshitake and Yoshihara [J. Vac. Sci. Technol. A13 (1995) 2407] for the Cu-segregated Ti emitter. This discrepancy indicates the importance of the structural difference between the segregated and metal-deposited surfaces, which has not been considered in the study of the change in the work function due to surface segregation.