Nanostructuring and oxidation of diamond by two-photon ultraviolet surface excitation: An XPS and NEXAFS study

Abstract

We report C(1s) and O(1s) surface sensitive x-ray photoelectron spectroscopy (XPS) and C and O K-edge partial-electron yield near-edge x-ray absorption fine structure (NEXAFS) measurements for (100) and (110) oxidized diamond surfaces, etched by a laser two-photon ultraviolet (UV) desorption process. Etched regions of the (100) surface show increased oxygen coverage with a higher fraction of singly bonded termination species than unetched regions. Similar changes are observed for the (110) but with smaller magnitude. For both surfaces, no major change in sp2 bonded carbon is observed. We show that the terminations observed for etched surfaces are consistent with the formation of oxidized {111} facets. For deeply etched samples, atomic force microscopy and scanning electron microscopy confirm the presence of {111}-like facets and reveals the development of nanoscale facetted ridges directed perpendicular to the etching beam polarization. An etching mechanism is proposed involving localized optical absorption by surface electronic states, with the probability for subsequent desorption events varying according to the relative directions of laser polarization and lattice orientation. © 2014 American Physical Society.