Near ambient pressure photoemission spectroscopy of metal and semiconductor surfaces

Abstract

AbstractWe describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metal and semiconductor surfaces (Al, Ag, Au, Si) illuminated by a Deep Ultra‐Violet (DUV) source at ambient pressure. In Constant Final State Yield Spectroscopy (CFSYS) the incident photon energy is rastered rather than applying a variable retarding electric field as in conventional UPS. For both ambient‐ and near ambient pressure‐photoemission spectroscopy (NAP‐PES) the CFSYS configuration overcomes the limitation of inelastic electron scattering in air. This arrangement can be applied in several operational modes: using the DUV source to determine the absolute work function (ϕ) of the metal with 50‐100 meV resolution and also the Kelvin probe, under dark conditions, to measure Contact Potential Difference (CPD) with an accuracy of 1‐3 meV. We show that the metal photoresponse agrees with Fowler theory. We have used CPD and linear extrapolated photoemission measurements to produce an energy level diagram for the native‐oxide covered Si. We propose a model of photoemission in air involving atmospheric ions. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)