Quantitative measurements of high resolution electron microscope images have show that the lattice fringe contrast is much lower than predicted by image simulations, typically by a factor of about three (the Stobbs factor). The search for the cause of this problem has ruled out many possible causes and quantified the contributions from inelastic and phonon scattering. Current work is concentrating on accurate measurements of contrast under different conditions and methods to determine the degree of coherency.
Long focal series of high-resolution images contain information enabling the exit surface wavefunction to be determined. Linear restoration is the established method for exit surface wave restoration. Iterative restoration is under development.
Lorentz images show the boundaries of domains in magnetic materials by imaging away from focus. Methods are being developed to derive the strength and direction of the magnetic field from Lorentz images.
Characterisation of semiconductor devices using TEM techniques.
IMRE's in-situ TEM has been used to study the epitaxial growth of Co and Ni on Si, Ni on Ge, Ni on MgO and the growth of boron nitride from FeB.
Structure and characterisation of nanomaterials such as Ag2Se and ZnS
Characterisation of field-emission grown tungsten nanowires.
Materials diffuse through diffusion barriers via the grain boundaries. Amorphous materials have no grain boundaries so should make better diffusion barriers.
Methods for the preparation of plan-view and edge-on samples plus associated artefacts
Fresnel contrast was developed by Dr WM Stobbs' group as a technique for determining interfacial properties. Boundary widths and projected potentials can be determined from bright-field and dark-field focal series by comparison with image simulations.
The atomic structure of the boundaries in semiconductor heterostructures, such as GaAs/AlGaAs determines their electrical properties. But their epitaxial nature makes imaging difficult. Techniquies are developed for imaging and characterising the layers on the atomic scale.
Inelastic scattering was suspected to be a contribution to high resolution images even before its contribution could be determined using imaging filters. Its contribution was deduced by comparision of experimental and simulated high-resolution centre-stop images.
Investigation of the approximations in multislice simulations to deal with upper Laue zones.
Developments of electron energy loss spectroscopy and energy filtered imaging.
The structure of polymers determined using neutron scattering and electron microscopy.
The resolution of electron beam lithography is limited by the PMMA resists used. Alternatives investigated include AlF3 and Al2O3 resists and resistless lithography of SiO2.
Techniques for the characterisation of the microstructure of alloys.
Characterisation of carbon nanotubes, tungsten sulphide nanotubes and carbon nanotubes coated in one or two monolayers of tungsten sulphide.
Characterisation of semiconductor structures using HAADF.
TEM techniques for the characterisation of materials.
The resolution of traditional X-ray lithography is limited by the spreading of the X-rays between the mask and the resist. By making use of Fresnel diffraction it is possible to decrease the linewidth by up to a factor of 5.
Measurement of strains in semiconductor devices using convergent beam electron diffraction.