Probing of Nanostructured Surfaces Probing of Nanostructured Surfaces at Attosecond Timescalesat 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.

NPRLNanoscale Physics Research Laboratory

Current Group InterestsCurrent Group Interests

• Gold FingersGold 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.

NPRLNanoscale Physics Research Laboratory

(150nm x 150nm)

1 Q. Guo, F. Yin, R. Palmer, small (1) 76-79 (2005)

Finger Width 3nm - 8nm

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

Proposed Work –TiOProposed Work –TiO2 2 (110) Surface(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.

NPRLNanoscale Physics Research Laboratory

Nanostructured SurfacesNanostructured 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

tE.

NPRLNanoscale Physics Research Laboratory