Ab-Initio Modeling of Point Defects, Impurities and Diffusion in Silicon

We have revisited the first-principles calculation of the diffusion coefficient for nitrogen monomers and dimers, both within the dissociative and the direct pair-diffusion picture, using density-functional theory and harmonic transition-state theory. From our current understanding, it seems that the results for the dissociative mechanism are in better agreement with experiment than those for the direct pair-diffusion mechanism. Based on a monomer diffusion coefficient of D(T) = 7.3e-3 exp[-0.53 eV/(kT)] cm^2/s, we calculate for the dissociation diffusion parameter of the dimer P = 1.6e9 exp[-2.4 eV/(kT)] cm^(1/2)s

Contactless and absolute linear displacement detection based upon 3D printed magnets combined with passive radio-frequency identification

Within this work a passive and wireless magnetic sensor, to monitor linear displacements is proposed. We exploit recent advances in 3D printing and fabricate a polymer bonded magnet with a spatially linear magnetic field component corresponding to the length of the magnet. Regulating the magnetic compound fraction during printing allows specific shaping of the magnetic field distribution. A giant magnetoresistance magnetic field sensor is combined with a radio-frequency identification tag in order to passively monitor the exerted magnetic field of the printed magnet. Due to the tailored magnetic field, a displacement of the magnet with respect to the sensor can be detected within the sub-mm regime. The sensor design provides good flexibility by controlling the 3D printing process according to application needs. Absolute displacement detection using low cost components and providing passive operation, long term stability and longevity renders the proposed sensor system ideal for structural health monitoring applications.Comment: 4 pages, 5 figures, 1 tabl