Atomic step disorder on polycrystalline surfaces leads to spatially inhomogeneous work functions

Structural disorder causes materials’ surface electronic properties, e.g., work function (ϕ), to vary spatially, yet it is challenging prove exact causal relationships underlying ensemble disorder, roughness or granularity. For polycrystalline Pt, nanoscale resolution photoemission threshold mapping reveals a spatially varying ϕ=5.70±0.03 eV over distribution of (111) vicinal grain surfaces prepared by sputter deposition and annealing. With regard field emission related phenomena, vacuum arc initiation, salient feature the ϕ that skewed with long tail values down 5.4 eV, i.e., far below mean, which exponentially impactful via Fowler–Nordheim relation. We show spatial variation can be explained variations granular tilts slopes Smoluchowski smoothing model wherein local result from densities electric dipole moments, intrinsic atomic steps, locally modify ϕ. Atomic step-terrace structure confirmed scanning tunneling microscopy (STM) at several locations on our surfaces, prior works showed STM evidence for step dipoles various metal surfaces. From model, we find an edge μ=0.12 D/edge atom, comparable reported in studies utilized other methods materials. Our results elucidate connection between macroscopic nanostructure may contribute spread Pt useful toward more complete descriptions metals models electronics initiation.