SCANNING ELECTRON MICROSCOPY
The images obtained in the scanning electron microscope are produced by secondary electrons or backscattered electrons emitted as a result of the interaction between an incident beam of 0,02 to 30 KeV and the sample.
As a result of the scanning of an electron beam across the surface of the sample in XY, an image can be formed on the monitor. The brightness of each point on the screen is proportional to the signal emitted by the sample at that point.
The secondary electron signal is emitted from a thin layer of the surface ranging from 50 to 100 Å. Low-energy electrons, less than 50 eV, can be easily deflected from their emerging trajectory giving information from areas hidden to the detector. So the signal can provide information about the topography of the sample.
The backscattered electron signal depends strongly on the atomic number of the sample. This means that two parts of the sample with different composition appear with different intensity even if there is no difference in topography between them.
The X-rays generated from the scattering of the electron beam in the sample allow the identification of the elements present in the sample and their concentration.
There are many applications of the technique both in materials science and biomedical science. Materials science applications include metallurgy, petrology and mineralogy, building materials, traditional and advanced ceramics, electronics, fractography, composites and the study of elemental composition of surfaces and solids in general. The SEM is also used in botanic, in the study of cell cultures, in dermatology, in biomaterials, in odontology, in hematology, in immunology, and in the study of the morphology of biomedical preparations in general.
- Scanning electron microscope Hitachi S3000N. This microscope is equipped with an X-ray detector Bruker XFlash 3001 for microanalysis (EDS) and mapping. The scanning microscope is able to work in variable pressure mode for observation of nonconductive specimens without coating with any conductive material.
- Field emission scanning electron microscope (FESEM) Merlin VP Compact from Zeiss equipped with an EDS microanalysis system Quantax 400 from Bruker. The resolution is 0.8 nm at 15 kV and 1.6 nm at 1 kV. Field emission equipment is able to work at voltages very reduced (from 0.02 kV to 30 kV) allowing to observe beam sensitive samples without damaging them and minimizing the charging effects.
Co-financed by 80% by the ERDF 2007-2013 of the Comunitat Valenciana and 20% by the Generalitat Valenciana
Equipment for sample preparation:
- Coater Balzers SCD 004
- Coater Balzers MED 020
- Coater Quorum Q150T ES Plus
- Vacuum Dry Oven J.P. Selecta VACIOTEM-TV 4001490
- Samples must be delivered properly labeled, packaged and conditioned to ensure their identification, integrity and conservation during transport and to guarantee the safety of the person who handles them.
- Samples must be conductive, solid and free of moisture, solvents and liquids in general.
- Samples should be as smaller as possible according to the particular features of each one accepting as maximum size 4 cm in diameter and 1 cm in height for SEM and 1 cm in diameter and 0.5 cm in height for FESEM.
- Samples melting point should be above 100 ºC.
- If samples are non-conductive they will be covered with conductive material at the discretion of the technical staff.
- If the technical staff consider it necessary, the samples will be subjected to a vacuum heat treatment.
- Regardless the nature of the sample it will be always prepared on the appropriate support to be observed under the microscope.