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O: Oberflächenphysik

O 30: Methodisches (Experiment und Theorie)

O 30.8: Vortrag

Donnerstag, 14. März 2002, 13:00–13:15, H44

Investigation of elastic waves generation in a solid target by a pulsed ion beam — •Chavkat Akhmadaliev and Lothar Bischoff — Instut für Ionenstrahlphysik und Materialforschung, FZ Rossendorf, Bautzner Landstraße 128(B6), 01328, Dresden

The generation of elastic waves in solids during irradiation with pulsed ion beams was investigated. There are two main mechanisms of the elastic wave emission. First is a simple momentum transfer from the beam particles to the target atoms. Also the heating of the material yields an acoustic wave due to a local thermal expansion. Other effects, like a change of the density, local amorphization, charging up of the target near the surface etc. can also generate elastic waves. The waves can be registered on the surfaces of the sample. The measurements are carried out using a IMSA-100 focused ion beam (FIB) system and a 3 MV-TANDETRON accelerator. The energy of the FIB was 30-35 keV at a current of 1-3 nA and a spot size of about 1 micron. On the accelerator a current of some microamps and energies up to some MeV with Au⁺, Ge²⁺, Si²⁺, Si³⁺ and Si⁴⁺ ions were used. The elastic waves were registered by a piezoelectric sensor on the back surface of the sample. Then the signal is amplified and digitized on a PC. The dependence of the amplitude of the acoustic signal in silicon, titanium, brass and aluminum are measured for different beams. The amplitude depends on the power of the beam linearly at low current densities. These elastic waves can be used for acoustic imaging of surface and buried structures in a scanning ion acoustic microscope.