Papers by Keyword: EPR

Abstract: The collaborative system for medical image and video analysis used via Internet provides convenience and efficiencies for dental clinic. The CSCW based dental clinic image & video signal processing technology can provide doctors located in different hospitals to achieve a cooperative diagnosis through the dental images tools, telemedicine, and electronic patient records (EPR) and video-conference. It would have very important application value and practical prospect in dental clinic healthcare processing and bring great benefits to small and medium dental clinical healthcare organizations.

Abstract: The results of an investigation of the point defects (PD) generation, redistribution and interaction with impurities in the Si-SiO₂ system during the process of its formation in use of of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectra are presented. The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation conditions: temperature, cooling rate, oxidation time and impurity content. The difference between interface properties of n- and p-type wafers could be related to different Fermi level position at the interface and to different PD densities in volume.

Abstract: The results of the investigation of stresses relaxation by strain by means of EPR spectra, IR absorption spectra, SEM and samples deflection are presented. It has been shown that stresses relaxation mechanism depended on the oxidation conditions: temperature, cooling rate, oxide thickness. In the Si-SiO₂-Si₃N₄ system the stresses relaxation by the strain occur due to the opposite sign of the thermal expansion coefficient of Si-SiO₂ and Si₃N₄ on Si. Laser irradiation allows to modify the system stresses.

Abstract: The electron paramagnetic resonance (EPR) technique was employed to investigate the point defects in barium strontium titanate ceramics. All samples showed a strong EPR signal with g = 2.000, which was indexed as intrinsic Ti-vacancy defects. In (Ba_0.85Sr_0.15)TiO₃ ceramic, which showed a tetragonal symmetry and consisted of the crystallites with average size of ~ 220 nm, a novel EPR powder spectrum was observed - the g-factor of the g = 2.000 signal evolved into a g-tensor, and the two weak signals with g₃ = ~ 2.6 and g₁ = ~ 1.6 gradually shifted toward the g2 = 2.000 signal and approached to each other with increasing temperature.

Abstract: The EPR parameters and the local structure for Co2+ in ZnO are deduced from the perturbation formulas of these parameters for a 3d7 ion in a trigonally distorted tetrahedron. The ligand orbital and spin-orbit coupling contributions are taken into account uniformly from the cluster approach in view of the covalency of the system. The impurity V3+ is found not to locate exactly on the Zn2+ site but to experience a small displacement of 0.04 Ǻ away from the ligand triangle, along the C3 axis. The theoretical EPR parameters based upon the above impurity displacement are in good agreement with the observed values.

Abstract: It has been shown by means of EPR and NMR technique that at the Si-SiO2 interface at appropriate oxidation temperature (time) local dynamical equilibrium may be achieved. At oxidation temperature 1130oC the dencity of point defects is less than at lower and higher temperature (1100oC and 1200°C) and the content of absorbed impurities (hydrogen, oxygen) diminishes.

Abstract: Silicon p-type (100) wafers implanted with Ni, Co, Fe ions to a dose range of 3∙1013–3∙1016 cm-2 have been investigated by means of EPR. The g-factor from dangling bonds of silicon modified by Ni, Co, Fe ion implantation is found to be different from the g-factor of amorphous silicon explained by the change of the local magnetic permeability r. Extreme character of the spin concentration on dose dependence is found, being not typical for silicon.

Abstract: The results of investigation of the point defect generation and interaction with impurities in the Si-SiO2 system during the process of its formation by means of electron paramagnetic resonance (EPR) and nucleous magnetic resonance (NMR) technique are presented. It has been shown that the diference in point defects interaction with hydrogen at the Si-SO2 interface with n- and p-type conductivity are connected with the sign of hydrogen ions incorporation dependence on the Fermi level position in accordance with the proposed model. The interface properties may be improved by laser irradiation.

Abstract: Nanoparticles of palladium were obtained with the help of hydrogen-oxidising, metal- reducing bacteria and used for the production of electricity in a proton exchange membrane (PEM) fuel cell. Earlier works have shown that palladised cells of Escherichia coli and Desulfovibrio desulfuricans (Bio-PdE.coli and Bio-PdD.desulfuricans, respectively) appeared similar by electron microscopy and were comparably active in a chemical test reaction. When tested in a PEM fuel cell they produced 0.018 and 0.108 W, respectively. Electron paramagnetic resonance analysis of Bio-PdE.coli mixed with activated carbon showed paramagnetic activity. However, Bio-PdD.desulfuricans under the same conditions quenched the intrinsic EPR signal. This quenching is indicative of the magnetic properties of the particles. The magnetic behaviour of Pd nanoparticles was theoretically predicted for particles between 10 and 20 nm in diameter and can be experimentally confirmed by EPR measurements.

Abstract: Defects introduced by electron irradiation at ~80-100 K in 3C-, 4H- and 6H-SiC were studied by electron paramagnetic resonance (EPR). A number of EPR spectra, labelled LE1-10, were detected. Combining EPR and supercell calculations, we will show that the LE1 center in 3C-SiC with C2v symmetry and an electron spin S=3/2 is related to the (VSi-Sii)3+ Frenkel pair between the silicon vacancy and a second neighbour Sii interstitial along the <100> direction. Results on other centers, possibly also related to interstitials, are discussed.