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A study of the response of three Δ E-E telescopes to fragments produced in nuclear interactions at 40 AMeV is presented. All the employed telescopes feature silicon carbide (SiC) detectors for at least one detection stage. Two identification methods have been used and their performance discussed: the Δ E-E technique and the Pulse Shape Analysis technique (for identification of nuclear fragments stopped in a single SiC layer). Identification capabilities similar to those obtained with the best available silicon detectors have been found for the SiC detector prototypes studied in this work.

Silicon carbide (SiC) is one of the compound semiconductor which has been considered as a potential alternative to Silicon for the fabrication of radiation hard particles detectors. Material, detectors implementation and possible application in the future INFN projects has been discussed.

Neutrinoless double beta decay (0 nu beta beta) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research “beyond Standard Model” and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0 nu beta beta decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0 nu beta beta Nuclear Matrix Elements. In DCE reactions and beta beta decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on beta beta matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0 nu beta beta.

The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article. © 2018, SIF, Springer-Verlag GmbH Germany, part of Springer Nature.

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The low temperature evolution of point defects induced in SiC by ion irradiation was investigated by deep level transient spectroscopy. The defects were introduced by irradiation with a 7.0 MeV beam of C+ ions at a fluence of 6 x 10(9) cm(2). Annealing was then performed in the temperature range of 330-400 K in order to study the change in point defect structure with temperature. The low temperature annealing performed was observed to induce a change in the produced defects. The deep levels related to the S-x (E-c - 0.6 eV) and S-2 defects (E-c -0.7 eV) recovered with annealing while, simultaneously, a new level, S-x (E-c - 0.4 eV), was formed. The activation energy of the S-1 defect is 0.94 eV, while the annealing of both the S-x and S-2 levels occurred with activation energy of 0.65 eV.

We have developed a high-quality growth process for 3C-SiC on on-axis (111)Si substrates with the ultimate goal to demonstrate high quality and yield electronic and MEMS devices. A single-side polished 50 mm (111)Si wafer was loaded into a hot-wall SiC CVD reactor for growth. The 3C-SiC process was performed in two stages: carbonization in propane and hydrogen at 1135¬?C and 400 Torr followed by growth at 1380¬?C and 100 Torr. X-ray diffraction rocking curve analysis of the 3C-SiC(222) peak indicates a FWHM value of 219 arcsec. This is a very interesting result given that the film thickness was only ,àº2 OEºm, thus indicating that the grown film is of very high quality compared with published literature values. X-ray polar figure mapping was performed and it was observed that the micro twin content was below the detection limit. Therefore TEM characterization was performed in plan view to allow assessment of the stacking fault density as well as confirmation of the very low micro twin concentration in this film. TEM analysis indicates a low concentration of stacking faults in the range of 10 4 cm -1. ¬© (2009) Trans Tech Publications, Switzerland.

High growth rate of 4H-SiC epitaxial layers can be reached with the introduction of HCl in the deposition chamber. The effect of the Cl/Si ratio on this epitaxial growth process has been studied by optical and electrical measurements. Optical microscopy shows an improvement of the surface morphology and luminescence measurements reveal a decrease of epitaxial layer defects with increasing the Cl/Si ratio in the range 0.05–2.0. The leakage current measured on the diodes realized on these wafers is reduced of an order of magnitude and DLTS measurements show a decrease of the EH6,7 level concentration in the same range of Cl/Si ratio. The value Cl/Si=2.0 allows to grow epitaxial layers with the lowest defect concentration.

The introduction of hydrogen chloride (HCl) in the deposition chamber during the growth of 4H-SiC epitaxial layers allows very high growth rates to be achieved. The properties of the epilayers and the growth rate depend on many parameters such as the growth temperature and the C/Si, Cl/Si, and Si/H-2 ratios. We have used optical and electrical measurements to investigate the effect of the Cl/Si and Si/H-2 ratio and growth temperature on the epitaxial growth process. The growth rate increases with increasing Si/H-2 ratio and higher growth rates are obtained when HCl is added to the gas flow. Optical microscopy shows an improvement of the surface morphology, and luminescence measurements reveal a decrease in the concentration of complex defects with increasing Cl/Si ratio in the range of 0.05-2.0 and with increasing growth temperature from 1550 degrees C to 1650 degrees C. The electrical measurements on the diodes realized on these epitaxial layers show a decrease of the leakage current with increasing Cl/Si ratio and growth temperature over the same range. Deep level transient spectroscopy measurements indicate that the deep level EH6/7, which is one of the main levels responsible for the high value of leakage current measured in the Schottky diodes, is greatly reduced using HCl as a growth additive.