Development of innovative characterization tools is of paramount importance to advance the frontiers of science and technology in nearly all areas of research. In order to overcome the limitations of individual techniques, correlative microscopy has been recognized as a powerful approach to obtain complementary information about the investigated materials. In order to get chemical information with a highest sensitivity and highest lateral resolution, we have combined SIMS with various high-resolution microscopy techniques (including Transmission Electron Microscopy, Scanning Probe Microscopy and Helium Ion Microscopy) and developed corresponding prototype instruments:
The AINA group has developed a compact SIMS add-on system which can be mounted on various instruments, including FIB and dual beam instruments, transmission electron microscopes, ion implanters, etc. The SIMS system includes extraction optics with a maximized efficiency and without negatively impacting the focusing of the primary ion beam, a compact magnetic sector double focusing mass spectrometer offering highest transmission (100 %), high mass resolution (M/DM > 2000), full mass range (H-U) and parallel detection of several masses.
We are developing field portable mass spectrometers, which are based on double focusing magnetic sector analyzer designs to reach high transmission, high mass resolution and parallel detection. The size of the spectrometers is depending on applications and can be as small as 20 x 10 x 10 cm3. The mass resolution (M/∆M) can be ranging from a few hundreds to a few thousands. Typical applications include isotopic measurements in hydrology, measurements in the oil and gas area, tracking of particles in the atmosphere, soil analysis, homeland security and space exploration.
Nano-scale techniques based on finely focused ion beams fall primarily into three groups: FIB machining, imaging (no chemical information) and analysis (chemical information). Such techniques all have in common that high-brightness ion sources are desired to produce very finely focused ion probes, and thus extremely high lateral resolution, while keeping a sufficiently high current compatible with a reasonable erosion rate or large yield of secondary electrons/ions. In addition, the species used for the ion beam is of great importance in all three areas mentioned above. Our ion source developments include a novel high brightness Cs+ ion source, negative surface ionization sources and versatile high-brightness electron impact ion sources.
Secondary Ion Mass Spectrometry (SIMS) is a well-established and extremely powerful technique for the chemical analysis of surfaces and thin films. Its main advantages are its excellent sensitivity, its high dynamic range, its good mass resolution and its ability to distinguish between isotopes. The use of cesium can dramatically increase the sensitivity of the analysis. We have therefore developed an add-on Cs deposition system allowing the sample surface to be coated with Cs prior to or during SIMS analysis for the purpose of optimizing analytical performances. This system presents several advantages, including increased sensitivities in the negative secondary ion mode (ionization probabilities of 100% for elements with high electron affinities), minimization or elimination of the matrix effect in the negative secondary ion mode and optimization of the sensitivities in the MCsx+ mode for efficient elimination of the matrix effect.
For ion-beam-based microscopy, the development of new instruments and applications requires the control of processes and mechanisms like particle sputtering and ionisation. We are therefore investigating particle – surface interactions by experimental studies and simulations (Monte Carlo, DFT and MD). The different aspects that are explored include sputtering, properties of sputtered matter (e.g. energy and angular distributions), atomic mixing and ionisation of sputtered matter.