Surface Patterning of Silver using an Electron- or Photon-Assisted Oxidation Reaction

We have investigated a recently developed method of patterning Ag surfaces. The method uses an electron beam to irradiate Ag surfaces during NO2 dosing at 300 K and leads to sharp oxide patterns on otherwise metallic surfaces. Investigations were performed on an Ag(111) single crystal and on an Ag foil with LEEM (low‐energy electron microscopy), LEED (low‐energy electron diffraction), MEM (mirror electron microscopy), and XPEEM (X‐ray photo‐emission electron microscopy). The oxidation reaction, which is based on the electron‐induced desorption of NO molecules, proceeds in steps, from a layer of O atoms adsorbed on the metallic Ag via an intermediate phase to an amorphous Ag2O film. Our measurements evidence a high cross section for electron‐induced NO desorption with 30–40 eV electrons, indicating that only a few electrons per adsorbing NO2 molecule are required to initiate the process. The intermediate phase, which forms a partially ordered quadratic structure, contains oxygen species in an oxide‐like environment, coexisting with an adsorbate covered metallic Ag(111) surface. While the intermediate phase dissolves within hours under UHV conditions, fully developed oxide patches, consisting of several layers of thick, amorphous Ag2O, are kinetically stable. The oxidation method also works with 40 eV (and 700 eV) photons instead of electrons. In preliminary experiments local patterns could also be created with photons, suggesting that mask techniques can be applied for the process. Silver surfaces can be patterned in a one‐step process applying an electron‐ or photon‐assisted oxidation reaction using NO2 as oxidizing agent. When adsorbing NO2 under a laterally confined irradiating beam, local Ag2O patches can be grown on a metallic Ag surface (see figure). Details on the process and the formation of intermediate phases during the growth process are discussed.