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Title: Monte Carlo study of variations in the surface sensitivity of energy-resolved x-ray absorption spectra from Ni/NiO thin-film bilayers

Abstract

The variation in the surface sensitivity of the x-ray absorption electron yield as a function of energy has been investigated for a Ni/NiO thin film bilayer sample. Experimental data was obtained using a recently developed detector capable of making energy-resolved electron yield x-ray absorption spectroscopy (XAS) measurements at ambient pressure. Datasets obtained using this technique contain information about the relative phase contribution to the XAS at each incident photon energy. Analysis of the data thus provides detailed information about the variation in surface sensitivity as a function of energy. This 'surface sensitivity profile' is studied using Monte Carlo simulations which include inelastic scattering events and discrete energy loss processes. Consideration of the electron multiplication/propagation processes within the sample provides an insight into the principles behind electron-yield signal formation. The simulations accurately reproduce the experimentally determined fraction of NiO in the XAS down to sub-keV energies. The results provide a reliable method for the independent determination of layer thickness in stratified samples and will aid in the future development of the technique.

Authors:
; ; ;  [1];  [2];  [2];  [2]
  1. Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW (United Kingdom)
  2. (United Kingdom)
Publication Date:
OSTI Identifier:
20853983
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 74; Journal Issue: 24; Other Information: DOI: 10.1103/PhysRevB.74.245408; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; AUGER ELECTRON SPECTROSCOPY; COMPUTERIZED SIMULATION; ELECTRONS; ENERGY DEPENDENCE; INELASTIC SCATTERING; INTERFACES; KEV RANGE; LAYERS; MONTE CARLO METHOD; NICKEL; NICKEL OXIDES; PHOTONS; SENSITIVITY; SURFACES; THIN FILMS; VARIATIONS; X RADIATION; X-RAY SPECTRA; X-RAY SPECTROSCOPY; YIELDS

Citation Formats

Abbey, Brian, Lipp, John D., Barber, Zoe H., Rayment, Trevor, CCLRC Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, and School of Chemistry, University of Birmingham, Birmingham, B15 2TT. Monte Carlo study of variations in the surface sensitivity of energy-resolved x-ray absorption spectra from Ni/NiO thin-film bilayers. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.74.245408.
Abbey, Brian, Lipp, John D., Barber, Zoe H., Rayment, Trevor, CCLRC Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, & School of Chemistry, University of Birmingham, Birmingham, B15 2TT. Monte Carlo study of variations in the surface sensitivity of energy-resolved x-ray absorption spectra from Ni/NiO thin-film bilayers. United States. doi:10.1103/PHYSREVB.74.245408.
Abbey, Brian, Lipp, John D., Barber, Zoe H., Rayment, Trevor, CCLRC Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ, and School of Chemistry, University of Birmingham, Birmingham, B15 2TT. Fri . "Monte Carlo study of variations in the surface sensitivity of energy-resolved x-ray absorption spectra from Ni/NiO thin-film bilayers". United States. doi:10.1103/PHYSREVB.74.245408.
@article{osti_20853983,
title = {Monte Carlo study of variations in the surface sensitivity of energy-resolved x-ray absorption spectra from Ni/NiO thin-film bilayers},
author = {Abbey, Brian and Lipp, John D. and Barber, Zoe H. and Rayment, Trevor and CCLRC Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX and Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB2 3QZ and School of Chemistry, University of Birmingham, Birmingham, B15 2TT},
abstractNote = {The variation in the surface sensitivity of the x-ray absorption electron yield as a function of energy has been investigated for a Ni/NiO thin film bilayer sample. Experimental data was obtained using a recently developed detector capable of making energy-resolved electron yield x-ray absorption spectroscopy (XAS) measurements at ambient pressure. Datasets obtained using this technique contain information about the relative phase contribution to the XAS at each incident photon energy. Analysis of the data thus provides detailed information about the variation in surface sensitivity as a function of energy. This 'surface sensitivity profile' is studied using Monte Carlo simulations which include inelastic scattering events and discrete energy loss processes. Consideration of the electron multiplication/propagation processes within the sample provides an insight into the principles behind electron-yield signal formation. The simulations accurately reproduce the experimentally determined fraction of NiO in the XAS down to sub-keV energies. The results provide a reliable method for the independent determination of layer thickness in stratified samples and will aid in the future development of the technique.},
doi = {10.1103/PHYSREVB.74.245408},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 24,
volume = 74,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • Transformation from an atomically stepped epitaxial thin film of NiO to a self-assemble nanotape structure at the step edge was observed in situ using synchrotron x-ray diffraction. The pristine NiO thin film was epitaxially grown on an ultrasmooth sapphire (0001) substrate with a regular step of 0.2 nm in height using laser molecular beam epitaxy. Transformation from the thin film to the nanotape structure was facilitated by postannealing in air from room temperature to 620 K. From the Arrhenius plot of ln(in-plane domain sizes) versus 1/T, an atomic-scale transformation energy of {approx}0.0135 eV/atom was derived.
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