For crystalline materials, IBA techniques can be combined with special geometries (beam aligned with a symmetry direction of the crystal) providing, not only compositional profiles, but also depth-resolved structural information. The channeling phenomenon is based on the steering of ions into the crystal lattice under such aligned conditions, which produces an intense reduction of the backscattering events (RBS/C), as well as in the emitted X-rays (PIXE/C) and gamma rays (PIGE/C). This decrease in the measured yield can be analyzed for different energies, elements and angles, allowing the study of a large variety of defects. Actually, channeling-based techniques have a high sensitivity to any lattice perturbation, including the detection of point and extended defects, strain, impurities, amorphous layers, phase separation, implantation damage, etc.
The Standard beamline at CMAM offers to the researchers a well-prepared chamber for ion channeling experiments, counting with a set of collimating slits (1 mm2 beam size), a 3-axis goniometer controlled by stepping motors (accuracy of 0.01º), and a fast home-made software for the alignment of the crystals. These elements can be combined with two particle detectors for RBS/C, and with further gamma ray or X-ray detectors. This system is a versatile and powerful tool for the characterization of epitaxial thin films, being a perfect complement to other structural techniques as XRD or TEM.
- Epitaxial growth: crystal quality, strain state, phase separation
- Defects: dislocations, impurities, lattice-site location
- Implantation damage and amorphous layers