G. Otto

A comparative study of swelling, strain and radiation damage of high-energy proton-bombarded GaAs, GaP, InP, Si and Ge single crystals

Abstract Swelling is studied on GaAs, GaP, InP, Si and Ge implanted with 0.3 and 1.2 MeV protons in the range of fluences D = 1015-8 × 1017cm−2, for several proton energies, implantation and annealing temperatures (T = 300–650 K). Within t the “buried” damaged layer all materials exhibit a volume dilation whereas in the near-surface layer only GaAs, GaP and Ge show considerable expansion and InP contracts due to the proton bombardment. For the interpretation of the results additional measurements of strain and damage density are taken into consideration.

Radiation damaging behaviour of GaP by MeV ion implantation

Abstract The creation of defects in GaP bombarded with energetic ions has been studied and compared with TRIM calculations. To investigate the influence of the relation of nuclear to electronic energy deposition and of the size of displacement cascades on defect production, the atomic species and projectile energies were varied from Z = 1 to 20 and E = 0.3 to 175 MeV. It has been found that not only the nuclear energy deposition but also the electronic energy deposition influences the defect production.

Fluorine profiling after application of various anti-caries gels

Abstract Two newly developed caries-preventing gels were tested together with Elmex R on pre-school children over a time of 3 years. Proton-induced gamma-ray emission spectrometry (PIGE) was used to measure the fluorine profiles in milk teeth (incisors). In accordance with the clinical statement the results allow to produce a new anti-caries drug.

PIXE channeling for concentration and location measurements of Zn- and Cd-dopants in InP single crystals

Abstract We present results of the determination of Cd- and Zn-dopants in InP single crystals using the PIXE and RBS spectrometry at our 2 MeV Van de Graaff accelerator. The (100) oriented crystals were doped by thermodiffusion of Cd and Zn atoms. For concentration and localization measurements we used the ion-channeling technique and energy dispersive spectrometry of proton induced X-ray emission (PIXE). Angular scans of the K-lines of In, Cd and Zn were obtained. The strong In X-rays were attenuated by a rhodium foil in front of the low energy Ge detector. The PIXE-channeling results were compared with SIMS and Hall-effect measurements.

Elemental analysis of mineral grains by means of simultaneous use of PIXE, PIGE and proton backscattering

Abstract Trace element concentrations in individual mineral grains can potentially provide direct information about the environment in which these minerals formed. Measurements were performed on mineral grains in polished rock slices and isolated minerals using the 2 MeV Van de Graaff accelerator at the University of Leipzig. The elemental contents of the geological samples were determined using the simultaneous measurement of proton induced X-ray and gamma-ray emission (PIXE, PIGE) and proton backscattering (PBS) in combination with electron probe micro analysis (EPMA).

The influence of surface topography on the depth resolution of the PIGE depth profiling technique

Abstract When calculating the depth resolution of the PIGE depth profiling technique, it can often be assumed that the target has an ideal smooth surface. However for many targets (enamel, ceramics) the surface roughness must be taken into consideration. A model of a rough surface was produced and was used to calculate the influence of experimental arrangement on the depth resolution. An approximate formula is given, from which the depth resolution of the depth profiling technique, applied to a rough surface (incidence angle ϑi = 0°), can be calculated.