EPSRC fundedMesoscale facilities at Daresbury

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EPSRC fundedMesoscale facilities at Daresbury
The UK Medium Energy Ion Scattering Facility
(MEIS)
The National Centre for Electron Spectroscopy and
Surface Analysis (NCESS)
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Medium Energy Ion Scattering

• Only instrument (of less than 10 world wide) to
  run as a facility providing a virtually unique
  capability to UK researchers
• A refinement of Rutherford Backscattering (RBS)
  with greatly enhanced resolution
• Uses light ions (50 to 200 keV H or He) to
  probe the surface and near-surface region

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MEIS Technique

• Elastic loss Large loss giving information on
  the mass of the target atom
• Inelastic loss- Smaller loss relating to the path
  length through the material
• Blocking Gives rise to angular variations in
  ion yield typical of material structure

MEIS determines the composition and structure of
materials with virtually monolayer depth
resolution
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Ion Beam Analysis of Archaeological Artefacts

• PIXE Pottery Fragments, Trace Elements in Wood,
  Provenance of Gems
• RBS Chemical analysis of Glassware Lustre,
  Ancient Tooth Enamel
• ERDA Trace Hydrogen Analysis in Diamonds
• MEIS - ????

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Enrichment in Al-0.4atCu Alloy

• Anodic oxidation leads to Cu enriched layer below
  the grown film
• Film is stripped using chromic/phosphoric acid
  before analysis
• Data reveals constant thickness of enriched layer
  with anodization time
• Increase in Cu content attributed to increased
  cluster generation

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Advantages and Disadvantages of MEIS

• Advantages over RBS
• Much higher depth resolution (2-5 Å)
• Structural Information (pm resolution)
• Disadvantages with respect to RBS
• Less quantitative
• Sample size 5mm2 to 15mm2
• Charging a problem for insulating samples
• Spot size 1mm x 0.5mm standard
• (0.2mm x 0.2mm minimum)

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The National Centre for Electron Spectroscopy and
Surface Analysis

• Scienta ESCA300 spectrometer
• High powered X-ray source (Al Ka and Cr Kb)
• Monochromated to reduce line width
• Additional high energy source (good for metal
  alloys)
• Large electron energy analyser with multi-channel
  detector for excellent resolution
• In-situ sample preparation facilities

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X-ray Photoelectron Spectroscopy

• X-rays penetrate sample surface
• Core level electrons ejected
• Core levels uniquely identify elemental
  composition
• Low escape depth gives surface sensitivity
• Small shifts in core levels reflect chemical
  environment of atoms

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Advantages of XPS

• Small spot size
• imaging possible!
• Insulating samples can be investigated (using
  flood gun)
• Ceramics
• Organic materials
• Biological samples
• Sample size 5mm2 to 20mm2

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XPS for Heritage Science

• XPS study of the atmospheric corrosion of copper
  alloys of archaeological interest
• Hayez et al, Surface and Interface Analysis 36
  (2004) 876
• Alteration and corrosion phenomena in Roman
  submerged glass fragments
• Barbana et al, J. Non-Crystalline Solids 337
  (2004) 136
• Organic substances at metal surfaces
  Archaeological evidence of the elder Plinys
  account
• Paparazzo, Archaeometry 45 (2003) 4

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Funding and Access

• Both facilities funded by responsive mode
• MEIS until 2010 (1.5M, 180 days per year,
  physics panel)
• NCESS until 2011 (1.2M, 160 days per year,
  materials panel)
• Access is effectively free for academic users
• Six-monthly applications and allocation meetings
• Users with grants specifying facility use
  automatically get time (MEIS- 65 of time NCESS-
  35 of time)
• Direct access users take residual time
• Priority for new users and contributors to the
  facility grant
• Industrial Links
• Via collaboration with academic users
• Option to buy time for commercial users
• (EU funded projects)

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Contacts

• Dr Tim Noakes MEIS
• Dr Paul Bailey MEIS
• Dr Graham Beamson NCESS
• Dr Danny Law NCESS
• Dr Steve Bennett MEIS NCESS

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SuperSTEM
5th order aberration corrected STEM recently
installed (SuperSTEM2)
Contact ian.godfrey_at_liverpool.ac.uk http//www.su
perstem.dl.ac.uk