Work function of Pt thin films with disorder*

Vacuum arcs are operation and failure mechanisms in numerous technologies for which predictive arc simulations could improve performance and lower cost. A challenge is that arc initiation is not well understood. Toward a better understanding of arc initiation, we investigate how nanoscale surface disorder on metal films influences electron emission. As a prototypical metal surface, we characterize polycrystalline Pt thin films that include grain boundaries, dislocations, crystal tilts, roughness, adsorbed gas, and thin dielectric layers. Using a toolset including scanning tunneling microscopy (STM), photoelectron emission microscopy (PEEM), and ultraviolet photoemission spectroscopy (UPS), we measure local work functions, from micrometer to Angstrom size scales. Work functions of clean Pt(111) approach 6 eV. Defects and coatings diminish the work function toward 5 eV. We connect our findings with values in a variety of prior works.