Research Projects: Advanced Characterisation

1 NANOTOMOGRAPHY AND 3D NANOMETROLOGY
Supervisor: G Möbus

Nanomaterials are intrinsically 3-dimensional materials, as their properties depend on surface-proximity and confinement, also referred to as low-dimensional matter. Imaging of surfaces or simple planar cross-sections is therefore no longer sufficient. In this project we develop new experimental acquisition sequences for applying the established method of computed axial tomography (CAT) to nanomaterials, where objects are rotated under irradiation around an axis, with special emphasis on 3D chemical and structural mapping. For students with skills and interest in computer software also the development of improved data reconstruction procedures will feature. State-of-the-art aberration corrected electron microscopy is available for projection imaging. Applications will comprise, depending on the interest of the student, e.g. nanoparticles, nanoparticle arrays, nanocomposites, functional nanotips and porous materials. This topic is an example of many more characterisation-based possible PhD topics, see www.moebus.staff.shef.ac.uk/phdtopics.pdf.

2 MATERIALS CHARACTERISATION BY ENERGY SELECTIVE SCANNING ELECTRON MICROSCOPY
Supervisor: Dr C Rodenburg

Scanning Electron Microscopes (SEMs) have been the workhorse for material science since the 1960s, mostly to visualise topography or material differences. In recent years much emphasis has been placed on the development of scanning microscopes that provide smaller probes size with the aim of achieving better resolution. Less attention is given to the detection of secondary electrons (SEs) in spite the fact that imaging using SEs of a certain energy range are expected to give better results in a number of applications such imaging magnetic materials, doping in semiconductors, mapping of electrical potential distributions. We have one of only a few SEMs worldwide that enables us to easily carry out energy selective with high lateral resolution. You will be expected to test the theoretical models experimentally and identify potential new applications for energy selective SEM. By doing so you could be instrumental in opening up a new era for SEM.

3 SITE SPECIFIC SAMPLE PREPRATATION TECHNIQUES FOR RAPID QUANTITATIVE DOPANT PROFILING IN THE SCANNING ELECTRON MICROSCOPE (SEM)
Supervisor: Dr C Rodenburg

Doping is the heart of all semiconductor devices because the dopants determine the electric properties of devices. The semiconductor industry has identified the need to measure dopant distribution in three dimensions with high spatial resolution and accuracy as one of the ten crucial requirements for the future of the industry. We have demonstrated such a two dimensional dopant mapping technique which relies on SEM images of cleaved semiconductors. However to be useful to the semiconductor industry we need to be able to use the technique at specific well defined sites of a device structure which can hardly be achieved by cleaving. A very well established technique for site specific sample preparation is the use of a focused ion beam (available at the Department Electronic and Electrical Engineering) but routine usage of such an instrument does not produce suitable specimens for dopant profiling in the SEM. You will be expected to develop a site specific sample preparation technique for semiconductor device structures that prove suitable for quantitative three dimensional dopant mapping using SEM.