Direct detection of electron–hole pairs generated by chemical reactions on metal surfaces

Non-adiabatic energy dissipation during exothermic chemical reactions on metal surfaces occurs by creation of electron–hole pairs in the metal. The excited charge carriers have been directly detected using metal–silicon (Schottky) diodes with ultrathin metal films. The chemically created hot electrons travel ballistically through the metal film, traverse the Schottky barrier and are detected as a chemicurrent in the diode. Three examples are presented, i.e. the adsorption of atomic hydrogen on Ag and Fe and the chemisorption of molecular oxygen on Ag. The chemicurrent transients upon exposure are related to the kinetics of the surface reaction. The large difference in the detection efficiency between Ag/Si and Fe/Si diodes is attributed to different conditions at the metal/silicon interface.