PhD at the
“Optimization of
nanometre scale optical microscopy” with Dr Andy Downes
Normally, optical microscopy is limited to resolving objects of size at least half the wavelength of light used: this resolution limit is typically ~200 nm when using visible light. However, using a very sharp atomic force microscope (AFM) tip, optical imaging and spectroscopy can be performed on the scale of ~10 nm. Light is scattered from beneath the tip apex, and the optical signal in this region is also greatly enhanced by the presence of the tip. The PhD student will perform simulations of this tip-enhanced optical microscopy, and characterize tips across the visible spectrum, using the best tips to perform ultra-high resolution optical imaging & spectroscopy. The optical properties which can be measured are scattering, fluorescence, Raman and coherent anti-Stokes Raman (CARS) – the latter two can map surface chemistry on the scale of ~10 nm. Using sharper tips, we aim to reduce this resolution towards 1 nm.
PhD research
programme
The successful candidate will:
- Use finite element modelling to simulate optical scattering spectra from sharp scanning probe tips – for a variety of materials and shapes – in air, and under water
- Use finite element modelling to simulate heat absorption spectra; combine with simulations of optical scattering
- Measure scattering spectra from commercially available AFM tips, with a white light source
- Measure scattering spectra from ‘homemade’ solid metal tips, and AFM tips which have been metal-coated at the Scottish Microelectronics Centre
- Measure the tip shape with a high resolution electron microscope, or an AFM test sample
- Measure the temperature rise under tip apex with a thermochromic fluorescent polymer – the wavelength of fluorescent light varies with temperature
- Use optimum tips for tip-enhanced optical spectroscopy and/or imaging in all these modes: scattering, fluorescence, 2-photon fluorescence, Raman, CARS
Left: (a) tip-enhanced
CARS and (b) height image of DNA nanoclusters. The CARS image is tuned to a
frequency of vibration of the adenine molecule. Centre: tip-enhanced fluorescence image of quantum dots. Right: arrangement of the novel set-up
for optical characterization of tips.
Informal Enquiries to Dr Andy Downes (tel: 0131 651 7072, e-mail: andy.downes@ed.ac.uk)
Closing date: 31 March 2010. Stipend 2010/11 £13650 tax free.
Funding is subject to approval by the