The dual beam microscope integrates the features of a field emission scanning electron microscope (FESEM) with a focused Gallium ion beam (FIB) microscope.
A FIB is comparable to a SEM, yet instead of electrons, it uses a beam of Ga+ ions. Ga+ ions are 130,000 times heavier than electrons; consequently, the interaction with the specimen is significantly stronger, whereas the penetration level is lower. Thus, ions produce a break of the chemical bonds and ionisation of the substrate atoms. Since the ion beam can be focused and monitored, this effect can be used to modify the structure of the specimen on a nanometric scale.
The advantage of combining both electron and ion columns on the same platform is that it enables us to simultaneously obtain high resolution SEM images and carry out modifications in the sample with the ion beam.
Typical applications for this type of equipment are: Cross sections, ultra-fine TEM sample (lamella) preparation, three-dimensional volume reconstruction of a specimen, and electron and ion lithography.
On the other hand, the FESEM can work independently, so when the FIB column is not necessary, the equipment can be used as a conventional FESEM.
The equipment in operation at the UPV Microscopy Service is the ZEISS AURIGA Compact model which incorporates the following detectors of the manufacturer:
A Secondary Electron Detector (SE2) which provides SEM topography images of the sample surface with a large depth of field. It is best suited to obtain medium and low resolutions with high acceleration potentials. It is mainly used to browse the sample at low magnifications in search of points of interest and to study samples with a large amount of topographic information.
A Backscattered Electron Detector (4QBSD) which is sensitive to the variation of atomic number in the elements present in the sample; therefore, it is used to observe changes in the chemical composition of the specimen. It comprises four quadrants and allows selection of images with topographic and compositional contrast.
A Secondary and Backscattered Electron Dual In-Lens Detector located inside the electron column. It has two working modes:
1. The Secondary Electron In-Lens Detector works with low energy secondary electrons and provides images with a higher resolution. It is very sensitive to the surface characteristics of the sample, which makes it very suitable for surface characterisation of any material. It performs best at low acceleration potentials (<5 kV), hence it is highly recommended both for working with electron beam sensitive samples and for minimising the charging effect on non-conductive samples.
2. The Backscattered Electron In-Lens Detector (EsB) allows us to obtain a pure backscattered signal at very low acceleration potential. It provides a great Z-contrast and can select the electrons according to their energy, which enables us to differentiate elements which can only be distinguished in a few atoms. It can also work at very low voltage (in the same range as the secondary in-lens detector), making it ideal for sensitive samples.
The Gas Injection System, GIS, (Orsay Physics) allows us to deposit Platinum on the surface of the sample. The injector introduces a precursor which is ionised by the Gallium ion beam and adheres to the specimen surface with precision.
The Micromanipulator (Kleindiek) permits extraction of the TEM samples carried out inside the equipment.