Electron emission channeling spectroscopy using X-ray CCD detectors

Abstract

The lattice sites of impurity atoms in crystals can be determined using the emission channeling (EC) technique. This method also provides information on the diffusion behavior and the defect interaction of impurities. In the EC technique, crystals are doped with radioactive impurity atoms and the anisotropic emission distribution of decay particles, preferably conversion electrons with typical energies of the order of 100 keV, are measured around different crystallographic directions. The measurement of EC spectra requires the energy- and angle-resolved detection of decay electrons with an angular resolution of typically 0.1°. We present first electron EC measurements using an energy- and position-sensitive CCD detector originally developed for imaging soft X-rays. We have prepared a sample by implanting radioactive 111In ( t 1/2=2.8 days) into Si (1 0 0) and subsequent annealing to 1173 K. In this sample In occupies substitutional sites and channeling effects, i.e. an enhanced emission yield, along all major crystallographic axes and planes is expected. The 〈1 0 0〉-axial electron emission distribution of 147 and 219 keV conversion electrons were recorded using a 64×200 pixel CCD for an angular range of ±2.9° vertically and ±8.5° horizontally. The CCD is an excellent detector for conversion electrons with extremely low noise and an outstanding energy resolution of about 3 keV FWHM at 219 keV. Future applications of CCD detectors for conversion electron spectroscopy are outlined.