OTHER FACILITIES | MICROSCOPY UNIT | TECHNICAL FEATURES
Scanning Electron Microscope (SEM)
The SEM of CLPU is an EVO®HD25 microscope supplied by Carl Zeiss Microscopy.
The SEM working procedure consists of a focused beam of accelerated electrons that scans the surface of a specimen. From the interaction of this electron beam with the sample, different types of signals can be collected by detectors installed in the vacuum chamber and processed by a control program to obtain high-resolution images (< 10nm).
- Electron thermionic gun with a LaB6 cathode (EVO®HD is equipped with a high-gloss source which, for low acceleration voltages, increases up to 10 times the brightness compared to standard LaB6 filaments)
- Large high vacuum chamber: 420 mm diameter and 330 mm heigh
- 5-axis motorized stage
- Carousel for up to 9 samples (12 mm bases)
- Working pressure ranges: high vacuum(10-4 Pa) and variable pressures (10 - 273 Pa)
General requirements of the samples (download)
- SE – Secondary Electron Detector of Everhart-Thornley type: enables working in a wide range of voltages (1kV - 30 kV) to obtain topographic and structural information of the sample surface.
- VPSE – Variable Pressure Secondary Electron Detector: suitable to prevent charging effects on non-conductive samples. The gas neutralizes the electrons trapped on the surface, stabilizing the emission of the secondary electrons.
- BSD – Backscattered Electron Detector of 5 segments: the emission of backscattered electrons from the sample is related to the atomic number of the elements that are present in it. This technique is of interest in geology, metallurgy, material physics, etc. Besides, in its topographic mode, it can reveal surface detail. It works in all vacuum modes.
- STEM – Scanning Transmission Electron Microscopy Detector: tin this type of microscopy, the detector is detected underneath the sample, so the specimen must be thin enough to allow electrons to pass through. The configuration allows the placement. The configuration allows the placement of the diode-type detector at a very short distance from the sample, thus improving the resolution, which is comparable to that of a BFTEM. It can work in variable pressure mode.
- EDS – Energy Dispersive X-ray Spectroscopy Detector: this device provides the chemical composition of a specimen by analyzing its X-ray emission. It is a technique widely used in material science, since, in addition to the information on the elements contained in the sample; it can give information about its surface distribution and even its concentrations. The detector is a 20 mm2 SDD from Oxford Instrument controlled by AZtec® software.
- EBS – Electron Backscattered Diffraction Detector: this technique can determine the crystallographic orientation of crystalline and semi-crystalline samples. The HKL Nordlys detector is controlled by AZtec® software and provided with CHANNEL 5® analysis program. More details about this technique at http://www.ebsd.com/.
The quality of the images depends largely on the preparation of the sample and it is essential for obtaining high-resolution images. The CLPU will not be involved in the preparation of the different specimens. Potential users are responsible for their correct preparation (coating, polishing, cutting...) according to the instructions provided in the General requirements of the samples document (updated 04/2020) that can be downloaded here.