Substrate effects on surface activation processes of graphene/metal composite photocathodes

Graphene is considered a suitable atomically thick layer on photocathodes, and the photoemission performance of the graphene-covered photocathodes can be enhanced through Cs/O activation. To investigate the effects of the substrate materials beneath the graphene layer on Cs/O deposition and photoemission performance. We compare the activation processes and photoemission performances of few-layer graphene supported by nickel and copper to investigate the effects of the substrate materials beneath the graphene layer on Cs/O deposition and photoemission performance. By Cs/O activation, the nickel-supported few-layer graphene can possess a higher response at 405 nm, while the copper-supported cathode can acquire a wider spectral response and better stability. After degradation, we discover that the samples supported by nickel and copper can act differently through the additional Cs/O deposition processes, while the surface barrier heights of both samples are further decreased.