Upgrading RBS analysis of single crystals by applicaton of triple correlation

摘要

Ion accelerators in combination with appropriate goniometers and detector systems have been widely used to investigate single crystals. In most of these measurements the information is obtained from the change in backscattering yield when a low index axis or plane becomes alighed with the beam. From a statistical point of view this decrease is due to a negative correlation between the projectile flux distribution and the target atom positions at the same depth. Using a `true' 180 deg detector, an additonal (positive) correlation between flux and local detector solid angle (or fraction of detected backscattered projectiles) can be obtained. A positive triple correlation exists when both, the beam and the detector are directed versus the same string of atoms at a small angle with the axis. We show that this yield (giving the `shoulder' in standard channeling measurements) is extremely sensitive to damage in the near surface region of the crystal.