Kroto Centre for High Resolution Imaging and Analysis
The Kroto Centre for High Resolution Imaging and Analysis is an advanced transmission electron microscopy (TEM) facility set up to conduct research at the forefront of world-leading resolution. The centre houses the JEOL Z3100R05 “R005” 80-300kV transmission electron microscope equipped with two aberration correctors (for ultra-high resolution) and a cold field-emission gun (for brighter illumination and improved energy resolution).
This instrument is currently unique within the UK and provides a spatial resolution approaching 0.05nm (0.5Å) for materials analysis as well as single atom imaging and spectroscopy capability.
The centre was formally opened by the Nobel Laureate, Prof. Sir Harry Kroto in June 2010 after which the instrument has undergone a number of modifications to establish its full specification.
The facility forms part of the Faculty of Engineering electron microscopy resources and is complemented by a fully analytical JEOL 2010F FEG-(S)TEM and a JEOL 6500F Fabrika dual beam FIB/FEG-SEM.
Key Features of the JEOL R005:
- 300kV c-FEG produces high brightness ultra fine electron probe with improved energy resolution (0.35eV) and current densities
- can be configured for 200kV and 80kV operation
- probe (STEM) and Imaging (TEM) aberration correctors (JEOL) providing sub-Å resolution
- fully dry vacuum system , with gun vacuum of ~10-9 Pa
- EDXS X-ray chemical analysis (JEOL)
- EELS and EFTEM via post-column spectrometer (Gatan Tridium GIF)
- remote operation control room to ensure ultra-stable microscope environment
- multiple camera options including bespoke CMOS based camera with selectable fast pixel readout, and second 2kx2k CCD camera
JEOL R005 Instrument Details
The R005 contains two sets of asymmetrical dodecapole corrector lens assemblies designed by JEOL. The upper aberration corrector eliminates the opening error of the probe-forming condenser lens system. This allows us to either focus the electron beam to ~1Å in diameter and perform scanning TEM (STEM) at this resolution, or we can generate a larger diameter electron beam that is similar in size to a conventional field-emission instrument but with significantly increased current (several nA within a few Ångstrøms). This is useful for improving the signal-to-noise ratio and/or reducing the acquisition time, and thus drift during mapping.
In scanning mode the images are generated on a computer screen by reading out on-axis (bright field) or off-axis (annular dark-field) detectors that record electron intensities at each point of the scan. Alternatively, electron energy-loss or characteristic X-ray signals can be mapped point-by-point. The lower aberration corrector eliminates the opening error of the main objective lens used for lattice imaging at high magnification with planar illumination.
Images can be recorded on several CCD cameras that are fibre-optically coupled to scintillator coated screens. We can thus improve the point resolution down to >1Å also in this mode and at the same time reduce image delocalisation effects by practically eliminating all transfer gaps up to very high spatial frequencies. As a result of this, the edges of specimens, interfaces and surfaces now appear atomically sharp and can be studied in-situ.
The post column electron energy loss spectrometer (Gatan™ Tridium) provides potential for energy-filtered imaging to map the distribution of certain elements, mostly light elements and transition metals, with ~1nm resolution. This is complemented by the energy-dispersive X-ray spectrometer (JEOL) offering ~2nm resolution and relatively fast elemental mapping of the lateral distribution of heavy elements.