Scanning Electron Microscopy (SEM)
- Focused Ion Beam Scanning Electron Microscopy (FIBSEM)
- Environmental Scanning Electron Microscopy (ESEM)
- Cryogenic Scanning Electron Microscopy (Cryo-SEM)
- Field Emission Gun Scanning Electron Microscopy (FEG-SEM)
SEM at a Glance
SEM is an imaging technique that uses incident electrons to generate secondary sample irradiance. This can then be analysed to visualise sample surfaces with high depth of field and lateral resolutions of around 1-20nm, as well as analyse the physical and chemical state of the substrate.
Right: ESEM imaging using the new FEI Quanta 650 allows high resolution imaging of uncoated or hydrated samples.
- FIBSEM couples traditional SEM with a focused ion beam that can be used for materials processing and sample preparation (deposition, ablation, sectioning etc.) or at low beam currents, for imaging in its own right.
- ESEM allows for the imaging of poorly conductive ‘uncoated’, or ‘wet’ samples that cannot be imaged in the high vacuum conditions of a traditional SEM.
- Cryo-SEM allows for biological samples to be rapidly frozen, prepared and then SEM imaged. This preserves the initial substrate morphology and chemistry of the fully hydrated specimen by preventing water loss to vacuum operation.
- FEGSEM uses a field emission gun electron source to generate a smaller diameter electron beam than standard thermal emission sources. This allows better spatial resolution to be achieved and makes the technique more suitable for nanostructural characterisation.
Applications of SEM
- Morphological and topographical investigations
- Compositional contrast imaging
- Chemical analysis via energy and wavelength dispersive X-ray spectroscopy (EDS, WDS)
- Dynamic macro-, micro- and nano-structural imaging under temperature, pressure and strain variations
- Sample manipulation, sectioning and thinning
How does SEM work?
A fine beam of electrons is used to scan across the specimen surface in synchronism with the spot of a cathode ray tube (CRT). This incident beam leads to elastic and inelastic scattering of electrons, as well as variations of electromagnetic radiation. There are subsequently a host of secondary signals that can be detected, including secondary electrons, backscattered electrons, Auger electrons, cathodoluminescence or X-rays. In general, as the primary electron beam is rastered across a substrate, the intensity of the secondary signal will change depending on the surface morphology, chemistry, physical state etc. The contrast is seen by adjusting the brightness of the CRT spot by the amplified version of this detected signal.
Images courtesy of Vladimir Korolkov Photography and Lubrizol Ltd.
Our SEM Facilities
Hosted at the Nanoscale and Microscale Research Centre (nmRC).
JEOL 7100F FEG-SEM
- JEOL in-lens Schottky field emissions source
- 3.0 nm resolution at 1 kV
- 1.2 nm resolution at 30 kV.
- GATAN Murano Heating Stage Module with heating up to 950oC.
- Oxford Instruments AZtec Energy Advanced X-max 150 EDS System for chemical characterisation.
- Oxford Instruments AZtec HKL Advanced EBSD System (with NordlysMax3) for crystallographic characterisation.
- Oxford Instruments INCA Wave 700 WDS System for high resolution elemental mapping and quantification.
JEOL 7000F FEG-SEM
- An alternative FEG-SEM
- Oxford Instruments INCA EDX system
FEI Quanta200 3D DualBeam FIB/SEM
(Cryo-SEM & ESEM facilities)
- Thermal emission electron optics with dual-anode source emission geometry and through-the-lens differential pumping.
- High-resolution (field emission) ion optics (Magnum™ column) with high-volume milling capabilities and an in-situ Omniprobe Model 100.7 nanomanipulator for sample milling, thinning, sectioning and lift-outs for more detailed structural SEM or TEM analysis.
- Quorum Technologies PP3010T Cryo-SEM Preparation System for cryogenic sample preparation and analysis, including freeze-fracture and freeze-etching.
- Oxford Instruments integrated INCA Energy 250 Microanalysis System for EDX elemental spectra and mapping.
- Gaseous secondary and backscattered electron detectors for imaging and analysis in a gaseous environment (ESEM).
- Gas Chemistry technology for enhanced milling rates including selective carbon Mill.
- High-precision specimen goniometer with 50 mm travel along the x and y axes.
- Automation serving unattended sectioning with full access to E-beam, I-beam, patterning and gas chemistry functionality.
- Tungsten metal deposition, carbon deposition, insulator enhanced etch (XeF2) and selective carbon mill gas injectors (2 fitted at one time)
FEI Quanta 650 ESEM
- High performance imaging in three modes: High Vacuum, Low Vacuum and ESEM.
- Water vapour, air and nitrogen ESEM imaging modes for hydrated or non-coated samples.
- GATAN in-situ Microtest tensile-compression stage MTEST200VT with loading up to 200N and Peltier temperature range -20oC to 160oC
- Variable vapour pressures with peltier based temperature control for relative humidity cycling/ adjustment sample freeze thaw cycling
- Alemnis in-situ Nano Indenter for micropillar compression and scratch testing
- Oxford Instruments X-Max -150 EDX Detector for high sensitivity chemical analysis.
- Peltier cooling stage for sample and humidity (gas pressure) control.
- High performance thermal emission SEM column with dual-anode source emission geometry
- High vacuum resolution: 3.0nm @ 30kV, 8.0nm @ 3kV
- Low vacuum resolution: 3.0nm @ 30kV, 10.0nm @ 3kV
- ESEM resolution: 3.0nm @ 30kV
FEI Quanta 600 Mineral Liberation Analyser (MLA)
- Combines EDS software by BRUKER and Mineral Liberation Analysis (MLA) software by JKTech/FEI that allows automated large area analysis of polished specimens to identify and quantify mineral composition and distribution.
- Outputs include calculated assay, elemental distribution, particle size distribution, modal mineralogy, mineral association, mineral locking etc.
- Can take up to 14 polished mounts at a time, or samples up to 150mm2 with automated analysis of each sample in turn.
- HV and LV operational modes with secondary or backscattered electron detection.
- Resolution reported at 3.5nm @ 30kV
JEOL JXA-8200 Electron Microprobe
- High resolution X-ray element mapping and quantification via wavelength dispersive x-ray spectroscopy (WDS).
- 4 wavelength-dispersive spectrometers (detectable wavelengths of 0.087 to 9.3nm).
- Detectable element range: B to U
- Analysable area 80 x 80mm, with magnification x40 to x300,000 (11mm WD).
- Specimen stage for 25mm polished blocks or thin sections.
- Digital secondary electron imaging with 6nm resolution (11mm WD, 30kV).
- Energy-dispersive spectrometry (EDX), backscattered electron detection.
Philips (FEI) XL30 SEM
- Standard imaging with EDX available.
JEOL 6400 SEM
- Standard imaging with EDX available.
JEOL 6060LV SEM
- Capable of low vacuum imaging and possesses a cryo facility for wet sample analysis at ultra low temperatures. A cold knife is available for freeze fracturing. EDX is also available.
JEOL 6490LV SEM
- Standard and low vacuum imaging with EDX and WDS available.
Publications of Interest
- Brown P.D., Edwards H.K., Fay M.W., (2010). Microscopy at the life sciences / physical sciences interface. Journal of Physics: Conference Series 241: 012019
- Edwards H.K., Fay M.W., Anderson S.I., Scotchford C.A., Grant D.M., Brown P.D., (2009). An appraisal of ultramicrotomy, FIBSEM and cryogenic FIBSEM techniques for the sectioning of biological cells on titanium substrates for TEM investigation. Journal of Microscopy. 234 (Pt 1): 16–25
- Edwards H.K., Coe S.C., Fay M.W., Scotchford C.A., Grant D.M., Brown P.D., (2008). Site-specific cross-sectional imaging of biomaterials and the cell / biomaterial interface using focused ion beam / scanning electron microscopy. Journal of Physics: conference series. 126:12097