Avaliable methods of research
SIMS analysis is based on exposure of the sample surface with primary ions possessing some definite energy, which is partially consumed
by the sample and induces emission of sÓ-called secondary ions. The secondary ions are subsequently collected and analyzed with mass-spectrometer
which allows to determine the elemental, isotopic, or molecular composition of the surface. The collision area is very small which provides a
high resolution of the technique.
As the particles are removed from the surface sample during the collisions, the technique (called as dynamic SIMS) may be used for etching
the surface or for obtaining the information from deep layers which is useful when working with thin films, layered structures etc. In order
to prevent an excessive removal of the surface atoms and to obtain the information from the initial intact surface, the surface of primary ions
should be low (<10-13 cm-2). The latter technique (static SIMS) is widely used for analysis of the surfaces of molecular structures.
Time-of-flight mass-spectrometry (TOF-SIMS) is based on the fact that ionis possessing a similar energy and differing by mass move with various
velocities. The secondary ions produced as a result of the collisions or ionized afterwards are accelerated with electromagnetic field and achieve
similar values of the energy. This results in a faster achievement of the detector with lighter atoms in comparison with heavier ones which
enables to record a mass-spectrum.
Modifications of the TOF-SIMS technique allow to obtain the information on the elemental, molecular or isotope composition of the surface,
elemental or isotope distribution over the surface, diffusion profile etc.
The analysis is carried out using a mass-spectrometer TOF-SIMS.5 (ION-TOF, Germany).
Basic characteristics of the apparatus:
- Mass range: 1 - 10000 a.e.w
- Mass resolution: 10000 (m/dm)
- Spatial resolution: 60 nm
- Depth resolution: up to 1 nm
- Etching rate: up to 10 ?m/hour
- Analysis depth: up to 1 nm
- Analyzed area: from several ?m2 up to several cm2