We describe a novel spectrometer designed for positron annihilation induced Auger electron spectroscopy employing a time-of-flight spectrometer. The spectrometer's new configuration enables us to implant monoenergetic positrons with kinetic energies as low as 1.5 eV on the sample while simultaneously allowing for the detection of electrons emitted from the sample surface at kinetic energies ranging from ∼500 eV to 0 eV. The spectrometer's unique characteristics made it possible to perform (a) first experiments demonstrating the direct transition of a positron from an unbound scattering state to a bound surface state and (b) the first experiments demonstrating that Auger electron spectra can be obtained down to 0 eV without the beam induced secondary electron background obscuring the low energy part of the spectra. Data are presented which show alternative means of estimating positron surface state binding energy and background-free Auger spectra.

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Articles you may be interested inChemical effect of Si+ ions on the implantation-induced defects in ZnO studied by a slow positron beam J. Appl. Phys. 113, 043506 (2013); 10.1063/1.4789010 Fluence, flux, and implantation temperature dependence of ion-implantation-induced defect production in 4H-SiC J. Appl. Phys. 97, 033513 (2005); 10.1063/1.1844618 Identification of vacancy-oxygen complexes in oxygen-implanted silicon probed with slow positrons J. Appl. Phys. 95, 3404 (2004); 10.1063/1.1652241 Vacancy-related defect distributions in 11 B -, 14 N -, and 27 Al -implanted 4H-SiC: Role of channelingThis report deals with studies concerning vacancy related defects created in silicon due to implantation of 200 keV per atom aluminium and its molecular ions up to a plurality of 4. The depth profiles of vacancy defects in samples in their as implanted condition are carried out by Doppler broadening spectroscopy using low energy positron beams. In contrast to studies in the literature reporting a progressive increase in damage with plurality, implantation of aluminium atomic and molecular ions up to Al 3 , resulted in production of similar concentration of vacancy defects. However, a drastic increase in vacancy defects is observed due to Al 4 implantation. The observed behavioural trend with respect to plurality has even translated to the number of vacancies locked in vacancy clusters, as determined through gold labelling experiments. The impact of aluminium atomic and molecular ions simulated using MD showed a monotonic increase in production of vacancy defects for cluster sizes up to 4. The trend in damage production with plurality has been explained on the basis of a defect evolution scheme in which for medium defect concentrations, there is a saturation of the as-implanted damage and an increase for higher defect concentrations. V C 2015 AIP Publishing LLC. [http://dx.

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Depth-resolved positron annihilation studies have been carried out on nitrogen-implanted Si to investigate defect evolution and thermal stability. Si(1 0 0) wafers have been implanted with 60 keV N+ ions to a fluence of 1 × 1014 and 1 × 1015 ions/cm2. From positron diffusion analysis of defect-sensitive S-parameter profiles, it is found that the higher dose sample undergoes a two-step annealing process consisting of annealing of deep level defects, followed by vacancy agglomeration near the surface at 873 K. For the low dose sample, however, nitrogen vacancy complexes are the only major defects remaining at 873 K. Annealing at 1073 K is sufficient to remove all kinds of open volume defects present in the samples.

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Novel nanocarbon hybrids of single-walled carbon nanotubes and dispersed nanodiamond: Structure and hierarchical defects evolution irradiated with gamma rays