Thermo Scientific Apreo SEMs
CEMAS’s Scanning Electron Microscope (SEM) capabilities underwent an exciting upgrade in autumn 2017 when we installed two new Thermo Scientific Apreo FEG SEMs. These instruments offer a wide variety of capabilities suitable for imaging and analysis of both hard and soft materials, from fracture analysis of welds to high resolution imaging of nanoporous polymers.
Apreo SEMs are specially designed for imaging with low voltage electron beams, rendering them capable of clearly seeing features under 10 nanometers in size, even in non-conducting materials. In addition to their outstanding imaging capabilities, the Apreo SEMs at CEMAS are highly versatile microscopes equipped with all the analysis tools commonly found on SEMs, including EDS x-ray detectors for composition analysis and EBSD cameras for crystallographic orientation mapping. These microscopes can be operated at typical SEM voltages from 30 kV to 200 V and beam currents spanning over five orders of magnitude from 1 pA up to 400 nA.
To assist with imaging and analysis of non-conducting materials, both Apreo SEMs can be operated under low vacuum conditions. In low vacuum mode, a small amount of ionizable gas is introduced into the chamber to assist with neutralizing the electron beam as it interacts with the sample surface. The gas used is typically water, which can be set to a maximum pressure of 500 Pa. This method allows for imaging of materials’ native surfaces without needing to coat them in carbon or metal. Metal coatings can often obscure small-scale features and/or hide subtle variations in composition throughout a material, so avoiding coatings can sometimes reveal information that would otherwise be missed. With some adjustments, all of the instruments’ other analytical tools are still available for use in low vacuum mode.
In addition to these features, the Apreos’ extensive capabilities include:
Electrostatic and electromagnetic focusing lenses, which helps achieve sub-nanometer resolutions even on magnetic samples.
Stage-biasing from -4000 V to +600 V, which creates an electric field between the sample and pole piece to 1) reduce the ‘landing energy’ of electrons when they hit the sample surface, 2) boost signal on the in-column detectors, and 3) facilitate analysis of non-conducting samples.
Versatile imaging detectors that drastically increase our ability to see different types of features in samples, including:
- Traditional Everhart-Thornley Detectors (ETD) for surface and topographical imaging using secondary electrons
- The Trinity suite of in-column detectors for high resolution imaging of both backscatter and secondary electron signals
- Retractable directional backscatter (DBS) detector with optional segmentation of either annular signals (ABS) for topographical backscatter imaging, or concentric signals (CBS) for enhanced composition and/or grain orientation contrast
- Retractable STEM detector for analysis of TEM specimens in the SEM
- Retractable Cathodoluminescence (CL) Detector for directly imaging red, blue, and green light generated by certain materials when exposed to high energy electrons, such as semiconductors and geological samples
Easy and rapid analysis of multiple samples thanks to a Multi-Purpose Stagein conjunction with a NavCam chamber mounted optical camera, which together allow users to load multiples samples and quickly navigate from one sample to the next with the Sample Navigation feature.
Four-quadrant imaging, capable of simultaneously collecting images from four different detectors at resolutions up to 6144 x 4096 pixels.
Active drift compensation for efficient auto-alignment of overlaid images to produce high signal-to-noise ratio final images, even if the sample moves slightly during image acquisition.
Plasma cleaners for automated in-situ sample and chamber cleaning.
MAPS software for automated collection, stitching, and blending of large area, high-resolution tiled images.
Platinum deposition system for patterning and depositing fiducial marks.
Remote operation capabilities from the CEMAS virtual learning digital theater and beyond, allowing users at other locations to fully utilize these instruments for teaching and research.
Our Apreo SEMs are also outfitted with high quality analytical equipment and software from EDAX:
Octane Elect 30 mm2 Energy Dispersive Spectroscopy (EDS) silicon-drift detectors (SDDs) for chemical composition analysis, capable of output count rates of 850,000 cps and equipped with ultra-thin silicon nitride windows for optimal detection and quantification of elements with low atomic numbers.
Hikari Electron Backscatter Diffraction (EBSD) cameras capable of acquiring up to 1400 frames per second for ultra-rapid crystallographic orientation mapping. These detectors are aided by the latest versions of TEAM and OIM analysis software, which have many exciting new features, including NPARTM and PRIASTM, which allow for even more rapid orientation mapping and characterization of materials as well as improved re-indexing of saved patterns during offline analysis.
These capabilities are combined via the Pegasus System, which enables simultaneous collection of EDS and EBSD data for advanced phase mapping.