Prosiectau Ffiseg ar gyfer myfyrwyr bl.3 a bl.4

Disgrifiad prosiect

Ellipsometry of Polymer Opal thin films

(supervisor: Chris Finlayson)

Nature of project: experimental, data analysis

Available to students on full-time physics degree schemes or joint students.

Project description and methodology

All the laws of optics that you know start to break down when we make materials which are structured on the sub-micron size-scale of the wavelength of light, often called photonic crystals (PCs).[1] A subcategory of PCs involves the packing of mono-disperse particles into ordered arrays, by various means, with well-defined periodicity. New optical effects are then possible such as photonic bandgaps, optical switching, and structural colour due to iridescence rather than absorption by a dye; this has a number of important analogues in nature.[2]

In this project, the student will study the optical properties of pre-prepared thin-films of polymer opals, in which the resonant wavelengths of the structures coincide with visible wavelengths.[3] Using the method of ellipsometry,[4] the key optical constants (n,k) may be measured and modelled as a function of wavelength, giving insights into the complex interactions of light scattering, diffraction and disorder within the sample.

A successful project will develop beyond the above in one/some of the following directions:
Comparison of samples operating at different parts of the visible spectrum and/or with differing refractive-index contrasts.

In the event of Covid restrictions to lab access, pre-existing ellipsometry data can be provided, and the emphasis will move towards developing multi-layer (and quasi 2D/3D) simulation models of such structurally coloured materials.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: As a Y4 project, further advancement may move towards developing multi-layer (and quasi 2D/3D) simulation models of such structurally coloured materials.

Please speak to Chris Finlayson (cef2) if you consider doing this project.

Initial literature for students:

  1. http://en.wikipedia.org/wiki/Photonic_crystal
  2. P. Vukusic and J. R. Sambles, Nature, vol. 424, p852 855 (2003)
  3. C. E. Finlayson et al., Adv. Mater., vol. 23, p1540 1544 (2011)

Novelty, degree of difficulty and amount of assistance required

Students will need to be trained on a number of pieces of lab equipment relating to spectroscopic techniques. Appropriate assistance and training will be given.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Lab training and sample familiarisationChristmas
Experimental phaseend of February
Data gathering completemid-March
Model development and data analysisEaster

Students taking this project will have to submit a full risk assessment form