Radiation Damage by Heavy Ions in Silicon and Silicon Carbide Detectors.

While silicon has been a steadfast semiconductor material for the past 50 years, it is now facing competition from other materials, especially for detector design. In that respect, due to its high resistance to radiation damage, silicon carbide is one of the most promising materials. In this work, we discuss the radiation damage studies of a new, large area, p-n junction silicon carbide device developed by the SiCILIA collaboration. We have studied the general performances of several devices, as a function of fluence, irradiated in different experimental conditions with different beams. A standard p-n junction silicon detector was also irradiated for comparison. The new detectors manifest excellent performance in terms of stability of the main parameters, linearity, defect distribution, charge collection efficiency, energy resolution, leakage current, etc. Experimental results evidence a radiation resistance of SiC devices more than two order of magnitude higher than Si devices. The new construction technology applied to silicon carbide material has made it possible to create very robust devices with excellent performance. These devices will soon be available for all those scientific projects where a high resistance to radiation damage is required.

Effect of Nitrogen and Aluminum Doping on 3C-SiC Heteroepitaxial Layers Grown on 4° Off-Axis Si (100).

This work provides a comprehensive investigation of nitrogen and aluminum doping and its consequences for the physical properties of 3C-SiC. Free-standing 3C-SiC heteroepitaxial layers, intentionally doped with nitrogen or aluminum, were grown on Si (100) substrate with different 4° off-axis in a horizontal hot-wall chemical vapor deposition (CVD) reactor. The Si substrate was melted inside the CVD chamber, followed by the growth process. Micro-Raman, photoluminescence (PL) and stacking fault evaluation through molten KOH etching were performed on different doped samples. Then, the role of the doping and of the cut angle on the quality, density and length distribution of the stacking faults was studied, in order to estimate the influence of N and Al incorporation on the morphological and optical properties of the material. In particular, for both types of doping, it was observed that as the dopant concentration increased, the average length of the stacking faults (SFs) increased and their density decreased.

Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes.

BACKGROUND: We aimed to investigate the effect of cell-cell dipole interactions in the equilibrium distributions in dielectrophoretic devices. METHODS: We used a three dimensional coupled Monte Carlo-Poisson method to theoretically study the final distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. The simulated distributions have been compared with experimental ones observed in the case of MDA-MB-231 cells in the same operating conditions. RESULTS: The real and simulated distributions are consistent. In both cases the cells distribution near the electrodes is dominated by cell-cell dipole interactions which generate long chains. CONCLUSIONS: The agreement between real and simulated cells' distributions demonstrate the method's reliability. The distribution are dominated by cell-cell dipole interactions even at low density regimes (105 cell/ml). An improved estimate for the density threshold governing the interaction free regime is suggested.