Probing of Nanostructured Surfaces at Attosecond Timescales

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Probing of Nanostructured Surfaces at Attosecond
Timescales

• Emma Catton

• 1st year PhD student in the Atomic Manipulation
  Group at NPRL
• Based in Birmingham for my first year then at
  Imperial College London to concentrate work on
  the STM.

NPRL Nanoscale Physics Research Laboratory
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Current Group Interests

• Gold Fingers
• Finger like structures were produced by scanning
  the STM tip at a step edge with constant voltage
  bias and increasing tunnel current.
• Fingers were produced at 90 and 150 to the
  discommensuration lines of the heringbone
  reconstruction1.

• Other Work
• Dissociation of aromatic molecules on silicon
  surfaces.
• Manipulation of gold clusters on graphite.
• Metal oxide semiconductors.

(150nm x 150nm)
Finger Width 3nm - 8nm
1 Q. Guo, F. Yin, R. Palmer, small (1) 76-79
(2005)
NPRL Nanoscale Physics Research Laboratory
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Proposed Work TiO2 (110) Surface

• Why TiO2?
• Considerably well studied in the past the surface
  is now well characterised. This makes it a good
  choice for studying new phenomena.
• Many applications including photocatalyst, solar
  cells, white pigment, corrosion-protective
  coating and optical coating.
• Irradiation by electrons or photons can give rise
  to desorption of O ions from the surface via the
  Knotek-Feibelman process. Known as electron or
  photon stimulated desorption (ESD or PSD).

• Proposed work
• Produce 1x1 reconstructed flat surface and
  investigate ESD at Birmingham
• STM studies of surface before and after laser
  irradiation. Possible PSD?
• Deposit metal such as Au onto surface. Gold is
  expected to diffuse to oxygen deficient sites.
• Nanostructures can be created.

NPRL Nanoscale Physics Research Laboratory
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Nanostructured Surfaces

• Consider a thin film
• Acts as 1D quantum well
• Quantum states can be studied using STS (Scanning
  Tunneling Spectroscopy) or photoemission
  spectroscopy.
• Pump and probe technique can be used to determine
  the lifetime of excited states. Electrons can be
  looked at in real time by varying time delay
  between pulses.
• Aim of my PhD
• To combine fast photon pulses and STM allowing
  analysis of surface processes at high spatial and
  temporal resolutions. This will provide a better
  understanding of the dynamical processes of atoms
  and electrons on solid surfaces.

1-2 nm
50nm
50nm
NPRL Nanoscale Physics Research Laboratory