High resolution positron-annihilation spectroscopy with a new positron microprobe

Abstract

In cooperation with Zeiss/LEO GmbH, a monoenergetic positron source has been integrated in the electron optical system of a scanning electron microscope by help of a magnetic prism. The electron optics serves both to image the specimen with electrons and to form a positron microbeam that allows local positron-annihilation measurements with a resolution in the micron range. The fatigue damage profile along the cross section of a copper plate after a three-point bending test has been investigated. The obtained S-parameter profile coincides well with the expected fatigue damage distribution.

Defect identification in semiconductors with positron annihilation: Experiment and theory

“…The latter is partly responsible for the small number of scanning positron microprobes (SPMs), comparable to a scanning electron microscope (SEM), as the focusing of the beam with reasonable intensity even at a large-scale facility results in spot sizes of the order of 5 m (Greif et al, 1997;Triftshäuser et al, 1997). Another limitation for the SPM is the lateral straggling and the positron diffusion length of several hundreds of nanometers in a perfect crystal that will limit the spot size even if the focus is improved.…”

Spatially resolved deformation studies on carbon steel employing X‐rays and positron annihilation

“…The DBAR measurements were performed at the Bonn Positron Microprobe (BPM) [8] with a positron energy of 30 keV collecting 3 × 10 5 events in the 511 keV annihilation peak. The beam diameter was adjusted to 100 µm to average over several grains.…”

Development of Positron Microbeam in AIST

“…In addition, fast positrons are emitted in all directions, and hence, the lateral resolution becomes larger. Therefore, the lateral resolution and spatial (volume) resolution of PAS with RI methods are several mm 2 and ~1 mm 3 , respectively. The diffusion length of the positrons in the materials (0-0.1 µm) is much smaller than the scale we are considering.…”

“…The advantage of such a SPM is that it can obtain two or three dimensional PAS images using the scanning lateral injection position (xy) and the implantation depth (z) of the focused beams, which allow the defect distributions to be visually evaluated. The AIST microbeam system [8] uses an electron linear accelerator (LINAC) to produce positrons [9,10], and consequently, its beam intensity (10 6 e + /s) is 10-100 times higher than those of the other SPMs [3][4][5][6], which use radioisotopes as the positron source. Therefore, the AIST microbeam system can obtain PAS images within a reasonable time (~10 3 pixels/hour) [11] and hence, SPM may be a practical tool.…”

“…Scanning positron microscopes (SPM) have been developed to apply PAS to very small samples or samples with small features of interest [3][4][5][6][7]. Slow positron beams of SPMs focus on samples where the beam spot size is less than a few tens of µm.…”