A scanning electron microscope (SEM) uses a focussed and scanned electron beam to produce a magnified image of a sample surface. The SEM comprises a tungsten filament electron gun, a lens system, scanning coils, an electron collector, and a cathode ray display tube. In the standard mode of operation, a SEM collects secondary electrons emitted from the sample surface. The contrast obtainable for samples comprising different materials is generally rather limited because the secondary electron emission coefficient is not a strong function of atomic number. Contrast can be improved by etching one of the materials prior to insertion in the SEM to create surface topology that can then be better imaged.
Zeiss EVO LS25 Life Science SEM
The Zeiss EVO SEM is able to image a wide variety of non-conducting materials and is specially designed to allow imaging in liquids. This allows biological samples to be imaged without any problems arising from sample dehydration. The Zeiss EVO SEM has a resolution of 3nm at 30kV, 10nm at 3kV and 20nm at 1kV. Integrated X-ray functionality allows for energy-dissipative x-ray spectroscopy (EDX/EDS) and x-ray fluorescence spectroscopy (XRF).
XRADIA nanoXFi Fluorescence Imaging Spectrometer
The Zeiss EVO SEM is equipped with an XRADIA nanoXFi Fluorescence Imaging Spectrometer for high resolution elemental analysis. This X-ray fluorescence system again uses the X-rays generated by the scanned electron beam in the SEM to perform chemical analysis of the specimen surface. However, the sub-100nm resolution allows the spatial distribution of elements in a sample to be mapped. Typical applications would be the spatial mapping of elements in an alloy and the imaging of defects in aluminium tracks in an integrated circuit.
IFG iMOXS Source/Oxford Instruments INCAx-act detector
The Zeiss EVO SEM is equipped with an IFG iMOXS X-ray source for trace elemental analysis in combination with an Oxford Instruments INCAx-act x-ray detector, which allows for both EDX (electrons in, x-rays out) and XRF (x-rays in, x-rays out). The IFG iMOXS provides high sensitivity trace analysis, with a spatial resolution of 50 micron. The sensitivity is element-dependent and can detect trace elements down to 50ppm. A typical application for the IFG iMOXS is analysis of the composition of glasses, as used for photonic applications.
Gatan XuM X-ray Computed Tomography
The Zeiss EVO SEM is equipped with a Gatan XuM for X-ray computed tomography. This is an imaging technique that provides 2D images of the internal structure of samples. A series of 2D images taken at different depths can then be reconstructed to provide a 3D image of the specimen. Typical applications would be in the life sciences for the analysis and reconstruction of biological specimens.