Scanning Electron Microscopy (SEM)
Scanning Electron Microscopy and Elemental Microanalysis (EDX)
Scanning Electron Microscopy (SEM) is an electron imaging technique used to characterise the morphology and microstructure of bulk sample materials. A finely focused electron beam is scanned across the sample and the electron signals generated (including secondary electrons and back-scattered electrons) are then amplified and detected to produce and image of the surface or near surface features of the sample. Another important signal generated when the incident electron beam interacts with the sample is the characteristic X-ray signal, which is used to determine the elemental composition of small or larger areas of the sample. To do this an energy dispersive X-ray microanalysis (EDX) system is used and if the sample is suitably prepared it is possible to perform quantitative elemental analysis. An alternative chemical microanalysis approach (for improved light element, trace element analysis and better spectral resolution) is to utilise the wave length of the X-ray signal using a wave length dispersive (WDX) system.
The nmRC is home to nine SEMs (all of which have EDX capability with WDX spectrometers on two of the SEMs). There is also a dedicated Electron Microprobe (EPMA) instrument which employs 4 wave length dispersive (WDX) spectrometers.
A summary of the more specialised nmRC capabilities include:
- Focussed Ion Beam (FIB) SEM uses a focused ion beam for materials processing and sample preparation (deposition, ablation, sectioning etc.) or at low beam currents imaging in its own right.
- Environmental SEM (ESEM) allows examination of fully hydrated 'wet' samples and of poorly conductive uncoated materials, all of which cannot be imaged in the high vacuum conditions of a conventional SEM.
- Cryo-SEM allows examination of rapidly frozen samples and subsequent fracturing to reveal the internal structure. This enables preservation of the true morphology and ultrastructure (and chemistry) of fully hydrated or liquid specimens.
- Field Emission Gun (FEG) SEM uses a high brightness electron beam with a high spatial resolution (compared to thermionic tungsten filaments) and therefore more suitable for imaging features on the nanoscale. Another advantage of a FEG source over thermionic emitters is the much improved performance at lower accelerating voltages (<5kV).
- Electron Microprobe (EPMA/WDX) - the lower peak to background inherent in the wavelength dispersive spectrum allows lower levels of detection and therefore much better analysis of trace elements compared to EDX. WDX is also better for light element analysis and the much improved spectral resolution means fewer spectral overlaps and more accurate analysis. The combination of the lower peak to background and the improved spectral resolution also produces 'cleaner' looking X-ray maps compared to EDX maps.
- Mineral Liberation Analysis (MLA) with EDX software allows automated large area analysis of polished specimens to identify and quantify mineral composition and distribution.
- Electron Back-scatter Diffraction (EBSD) is used to study crystal structure at the surface of a sample in the SEM, with a spatial resolution approaching that of the SEM image, by identifying crystalline phases and measuring crystal orientations. This can be combined with EDX to correlate elemental composition and crystal structure. By mapping an area it is possible to generate images showing the distribution of phases and orientation, to identify grain and sub-grain boundaries, to calculate grain statistics, and to analyse preferred orientation (crystallographic texture) using pole figures, inverse pole figures and the orientation distribution function.
- Secondary Electron Imaging
- Backscattered Electron Imaging
- Environmental SEM (ESEM)
- Field Emission Gun (FEG) SEM
- Focussed Ion Beam (FIB) SEM
- Cryogenic (Cryo) SEM
- Energy Dispersive X-Ray Spectroscopy (EDS/EDX)
- Wavelength Dispersive X-Ray Spectroscopy (WDS/WDX)
- Mineral Liberation Analysis (MLA)
- Electron Backscatter Diffraction (EBSD)
- 'In-situ' stages: Deben MicroTest Tensile-Compression Stage and Gatan Heating Stage up to 950 degrees
nmRC SEM Instrumentation
JEOL 7100F FEG-SEM
- JEOL in-lens Schottky field emission source
- 3.0 nm resolution at 1 kV
- 1.2nm 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 (MagnumTM 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
- Deben 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 300,000 (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 WDX available