Papers by Author: Vito Raineri

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Authors: Antonella Sciuto, Fabrizio Roccaforte, Salvatore di Franco, Vito Raineri, S.F. Liotta, Sergio Billotta, Giovanni Bonanno, Massimiliano Belluso
Abstract: The fabrication of high sensitive diodes array is very attractive for spectroscopic and astronomical UV imaging applications, particularly when visible light rejection is required. Wide band gap materials are excellent candidates for UV “visible blind” detection. In this paper, we demonstrate an array of Schottky UV-diodes on 4H-SiC with a single pixel area of about 1.44 mm2 and a total area of about 29 mm2. The Schottky photodiodes are based on the pinch-off surface effect, the front electrode being an interdigit Ni2Si contact that allows the direct light exposure of the optically active device area. For the proposed array, the optically active area is about the 48 % of total area. The single pixel dark current was below 0.1 nA up to –50 V and a fabrication yield of about 90 % was observed. The external quantum efficiency of the proposed array exhibits a peak of 45 % at the 289 nm wavelength and a visible rejection ratio > 4 ×103.
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Authors: Vito Raineri, Lucia Calcagno, Filippo Giannazzo, D. Goghero, F. Musumeci, Fabrizio Roccaforte, Francesco La Via
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Authors: Mariaconcetta Canino, Filippo Giannazzo, Fabrizio Roccaforte, Antonella Poggi, Sandro Solmi, Vito Raineri, Roberta Nipoti
Abstract: The surface morphology and the electrical activation of P+ implanted 4H-SiC were investigated with respect to annealing treatments that differ only for the heating rate. P+ implantation was carried out in lightly doped n-type epitaxial layers. The implantation temperature was 300 °C. The computed P profile was 250 nm thick with a concentration of 1×1020 cm-3. Two samples underwent annealing at 1400 °C in argon with different constant ramp up rates equal to 0.05° C/s and 40 °C/s. A third sample underwent an incoherent light Rapid Thermal Annealing (RTA) at 1100 °C in argon before the annealing at 1400 °C with the lower ramp rate. The ramp up of the RTA process is a few hundred degrees per second. Atomic Force Microscopy (AFM) micrographs pointed out that the surface roughness of the samples annealed at 1400 °C increases with increasing heating rate and that the critical temperature for surface roughening is above 1100 °C. Independently on the annealing cycle, Scanning Capacitance Microscopy (SCM) measurements showed that the P profiles are uniform over the implantation thickness and have plateau concentration around 9×1018 cm-3 in all the implanted samples. The fraction of P atoms activated as donors is 13% of the total implanted fluence.
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Authors: Filippo Giannazzo, Fabrizio Roccaforte, Dario Salinas, Vito Raineri
Abstract: In the present work, we systematically studied the effect of the annealing temperature (from 1400 °C to 1650 °C) on the electrical activation of 4H-SiC implanted with multiple energy (from 40 to 550 keV) and medium dose (1×1013 cm-2) Al ions. The evolution of the acceptor (NA) and compensating donor (ND) depth profiles was monitored by the combined use of scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM). We demonstrated that the electrical activation of the implanted layer with increasing annealing temperature is the result of the increase in the acceptor concentration and of the decrease in the ND/NA ratio. Atomic force microscopy (AFM) morphological analyses indicated that the surface quality is preserved even after the 1650 °C annealing process.
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Authors: Andrzej Misiuk, Barbara Surma, Jadwiga Bak-Misiuk, Vito Raineri
Abstract: The effect of treatment at up to 1400 K (HT) under enhanced hydrostatic pressure (HP, up to 1.2 GPa) on helium implanted single crystalline silicon (Si:He, He ion dose up to 6x1017cm-2, energy up to 300 keV) has been investigated by transmission electron microscopy, secondary ion mass spectrometry, photoluminescence and X-Ray methods. The treatment of Si:He at ≤ 920 K - HP results in a formation of buried nano-structured layers containing helium filled cavities/bubbles and numerous extended defects; many less dislocations are created at ≥ 1270 K in Si:He treated under HP. HP affects the recrystallization of amorphous Si, diffusivity of implanted He and of implantation-induced defects and thus promotes the creation of more but smaller He-filled cavities/bubbles as well as other defects near the range of implanted He+.
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Authors: Francesco Ruffino, Filippo Giannazzo, Fabrizio Roccaforte, Vito Raineri, Maria Grazia Grimaldi
Abstract: In this work, a methodology, based on a self-organization process, to form gold nanoclusters on the 6H-SiC surface, is illustrated. By scanning electron microscopy and atomic force microscopy the gold self-organization induced by annealing processes was studied and modelled by classical limited surface diffusion ripening theories. These studies allowed us to fabricate Au nanoclusres/SiC nanostructured materials with tunable structural properties. The local electrical properties of such a nanostructured material were probed, by conductive atomic force microscopy collecting high statistics of I-V curves. The main observed result was the Schottky barrier height (SBH) dependence on the cluster size. This behaviour is interpreted considering the physics of few electron quantum dots merged with the ballistic transport. A quite satisfying agreement between the theoretical forecast behaviour and the experimental data has been found.
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Authors: Francesco La Via, Fabrizio Roccaforte, Salvatore di Franco, Vito Raineri, Francesco Moscatelli, Andrea Scorzoni, G.C. Cardinali
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Authors: Patrick Fiorenza, Raffaella Lo Nigro, Vito Raineri, Dario Salinas
Abstract: The nano-characterization of thermal oxides grown on 4H-SiC is for the first time presented and analysed to derive its reliability. The dielectric breakdown (BD) kinetics of silicon dioxide (SiO2) thin films thermally grown on 4H-SiC has been determined by comparison between I-V measurements on large-area (up to 1.96×10-5 cm2) metal-oxide-semiconductor (MOS) structures and conductive atomic force microscopy (C-AFM) with a resolution of a few nanometers. C-AFM clearly images the weak breakdown single spots under constant voltage stresses. The stress time on the single C-AFM tip dot has been varied from 1×10-3 to 1×10-1 s. The density of BD spots, upon increasing the stress time, exhibits an exponential trend. The Weibull slope and the characteristic time of the dielectric BD events were so determined by direct measurements at nanometer scale demonstrating that the percolation model is valid for thin thermal oxide layers on 4H-SiC (5-7nm), but it fails for larger thicknesses (10 nm).
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Authors: Vito Raineri, Fabrizio Roccaforte, Sebania Libertino, Alfonso Ruggiero, V. Massimino, Lucia Calcagno
Abstract: The defects formation in ion-irradiated 4H-SiC was investigated and correlated with the electrical properties of Schottky diodes. The diodes were irradiated with 1 MeV Si+-ions, at fluences ranging between 1×109cm-2 and 1.8×1013cm-2. After irradiation, the current-voltage characteristics of the diodes showed an increase of the leakage current with increasing ion fluence. The reverse I-V characteristics of the irradiated diodes monitored as a function of the temperature showed an Arrhenius dependence of the leakage, with an activation energy of 0.64 eV. Deep level transient spectroscopy (DLTS) allowed to demonstrate that the Z1/Z2 center of 4H-SiC is the dominant defect in the increase of the leakage current in the irradiated material.
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