Electron-stimulated desorption of positive and negative oxygen ions from YBa2Cu3O7 surfaces

Abstract

Electron-stimulated desorption of positive and negative oxygen ions from YBa2Cu3O7 surfaces has been studied as a function of electron kinetic energy in the 70–600 eV range. It has been found that the threshold electron kinetic energy needed to induce positive oxygen ion desorption occurs at 260±5 eV, whereas that associated with negative oxygen ion desorption was found to be 100±5 eV. These electron kinetic energies correspond to Cu, Y, and Ba core-level binding energies. These results suggest that negative and positive oxygen ion desorption may be initiated via a primary core level ionization.

Photon stimulated desorption of hydrogen from diamond surfaces via core-level excitations: fundamental processes and applications to surface studies

“…Indirect desorption processes are initiated by energetic secondary electrons, which induce valence excitations, whereas direct processes proceed through the relaxation of core holes [3,4]. Desorption processes stimulated by core-level electronic excitations have been studied extensively in recent years, in particular for the negatively charged desorbing ions [5][6][7][8][9][10][11]. Studies of the ion fragments produced by the core-level excitations have yielded insight into dissociation pathways [12][13][14][15][16].…”

Photon-stimulated desorption ofH+andH−ions

“…3,4 Desorption processes stimulated by core-level electronic excitations have been studied extensively in recent years, in particular for the negatively charged desorbing ions. [5][6][7][8][9][10][11] Studies of the ion fragments produced by the corelevel excitations have yielded insight into dissociation pathways. [12][13][14][15][16] Many of these studies have shown that twohole, one-electron ͑2h1e͒ states, in which two holes are produced in valence band and one electron is excited to an antibonding level, are often responsible for ionic dissociation.…”

Resonantlike desorption of negative ions by core-level excitation under electron bombardment

“…Such behavior has been explained in terms of core-level ionization and subsequent interatomic Auger decay involving substrate atoms and adsorbates. 6 Only very recently have desorbing negative ions been attributed to core-level excitation processes, possibly resulting from charge-exchange processes [7][8][9] and/or involving the formation of excited substrate-adsorbate complexes. 7,10 In this paper, we present an observation of strong resonantlike behavior in negative-ion ESD spectra at electron energies corresponding to core-level excitation of substrate atoms.…”

“…Biasing is a standard method for enhancing sensitivity and is regularly used to extract energy thresholds in ESD. [7][8][9][10][11] The electron gun and optics used for electron bombardments ͑Riber CER 306 Auger and low-energy electron diffraction grazing angle electron gun͒ were not useful at electron energies below about 40 eV as a result of very small currents in the nA range. 12 In the 100-eV range, however, typical currents of 1-10 A into a spot size of a few mm 2 can be routinely achieved.…”

“…At electron energies above 300 eV, both H Ϫ and H ϩ yields rise to a plateau or broad maximum, indicative of threshold behavior previously observed in other systems. [7][8][9][10][11] The negative-ion spectrum exhibits interesting structure at electron energies less than about 300 eV, where well-defined peaks in yield are observed. Such strong structural features at high incident electron energies have not previously been observed, although some less pronounced structures have been found in ESD of H Ϫ from amorphous hydrogenated silicon ͑a-Si:H͒.…”