Browsing by Author "Vittone, E"
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- ItemCharge collection efficiency degradation induced by MeV ions in semiconductor devices: model and experiment(Elsvier, 2016-01-01) Vittone, E; Pastuovic, Z; Breese, M; Garcia Lopez, J; Jakšić, M; Raisanen, J; Siegele, R; Simon, A; Vizkelethy, GThis paper investigates both theoretically and experimentally the charge collection efficiency (CCE) degradation in silicon diodes induced by energetic ions. Ion Beam Induced Charge (IBIC) measurements carried out on n- and p-type silicon diodes which were previously irradiated with MeV He ions show evidence that the CCE degradation does not only depend on the mass, energy and fluence of the damaging ion, but also depends on the ion probe species and on the polarization state of the device. A general one-dimensional model is derived, which accounts for the ion-induced defect distribution, the ionization profile of the probing ion and the charge induction mechanism. Using the ionizing and non-ionizing energy loss profiles resulting from simulations based on the binary collision approximation and on the electrostatic/transport parameters of the diode under study as input, the model is able to accurately reproduce the experimental CCE degradation curves without introducing any phenomenological additional term or formula. Although limited to low level of damage, the model is quite general, including the displacement damage approach as a special case and can be applied to any semiconductor device. It provides a method to measure the capture coefficients of the radiation induced recombination centres. They can be considered indexes, which can contribute to assessing the relative radiation hardness of semiconductor materials. © 2016 Elsevier B.V.
- ItemDeveloping electronic devices capable of withstanding harsh radiation(2013-05-13) Pastuovic, Z; Vittone, E; Siegele, R; Capan, I; Vizkelethy, G; Cohen, DD; Jakšić, MStudies performed by Zeljko Pastuovic at ANSTO’s microprobe facility, in collaboration with a team of international researchers, are helping to understand, model and predict the detrimental influence of ionising radiation on semiconducting materials required in millions of electronic devices. The research aims to develop materials and devices that are able to better withstand the damaging effects of high energy particles present in harsh radiation environments, such as solar cells, and power satellites in space, as well as materials used in high-energy physics and accelerators. These studies will help semiconductor, aerospace and other industries to better understand and extend the life of electronic devices.
- ItemFocused ion beam fabrication and IBIC characterisation of a diamond detector with buried electrodes(Elsevier, 2011-10-15) Olivero, P; Forneris, J; Jakšić, M; Pastuovic, Z; Picollo, F; Skukan, N; Vittone, EThis paper reports on the fabrication and characterization of a high purity monocrystalline diamond detector with buried electrodes realized by the selective damage induced by a focused 6 MeV carbon ion beam scanned over a pattern defined at the micrometric scale. A suitable variable-thickness mask was deposited on the diamond surface in order to modulate the penetration depth of the ions and to shallow the damage profile toward the surface. After the irradiation, the sample was annealed at high temperature in order to promote the conversion to the graphitic phase of the end-of range regions which experienced an ion-induced damage exceeding the damage threshold, while recovering the sub-threshold damaged regions to the highly resistive diamond phase. This process provided conductive graphitic electrodes embedded in the insulating diamond matrix; the presence of the variable-thickness mask made the terminations of the channels emerging at the diamond surface and available to be connected to an external electronic circuit. In order to evaluate the quality of this novel microfabrication procedure based on direct ion writing, we performed frontal Ion Beam Induced Charge (IBIC) measurements by raster scanning focused MeV ion beams onto the diamond surface. Charge collection efficiency (CCE) maps were measured at different bias voltages. The interpretation of such maps was based on the Shockley-Ramo-Gunn formalism. (C) 2011 Elsevier B.V. All rights reserved.
- ItemGeneration of vacancy cluster-related defects during single MeV silicon ion implantation of silicon(Elsevier, 2014-08-01) Pastuovic, Z; Capan, I; Siegele, R; Jacimovic, R; Forneris, J; Cohen, DD; Vittone, EDeep Level Transient Spectroscopy (DLTS) has been used to study defects formed in bulk silicon after implantation of 8.3 MeV 28Si3+ ions at room temperature. For this study, Schottky diodes prepared from n-type Czohralski-grown silicon wafers have been implanted in the single ion regime up to fluence value of 1 × 1010 cm−2 utilizing the scanning focused ion microbeam as implantation tool and the Ion Beam Induced Current (IBIC) technique for ion counting. Differential DLTS analysis of the vacancy-rich region in self-implanted silicon reveals a formation of the broad vacancy-related defect state(s) at Ec −0.4 eV. Direct measurements of the electron capture kinetics associated with this trap at Ec −0.4 eV, prior to any annealing do not show an exponential behaviour typical for the simple point-like defects. The logarithmic capture kinetics is in accordance with the theory of majority carrier capture at extended or cluster-related defects. We have detected formation of two deep electron traps at Ec −0.56 eV and Ec −0.61 eV in the interstitial-rich region of the self-implanted silicon, before any annealing. No DLTS signal originating from vacancy-oxygen trap at Ec −0.17 eV, present in the sample irradiated with 0.8 MeV neutrons, has been recorded in the self-implanted sample. © 2014, Elsevier B.V.
- ItemMonte Carlo analysis of a lateral IBIC experiment on a 4H-SiC Schottkey diode(Elsevier B.V., 2011-10-15) Olivero, P; Forneris, J; Gamarra, P; Jakšić, M; Lo Giudice, A; Manfredotti, C; Pastuovic, Z; Skukan, N; Vittone, EThe transport properties of a 4H-SiC Schottky diode have been investigated by the ion beam induced charge (IBIC) technique in lateral geometry through the analysis of the charge collection efficiency (CCE) profile at a fixed applied reverse bias voltage. The cross section of the sample orthogonal to the electrodes was irradiated by a rarefied 4 MeV proton microbeam and the charge pulses have been recorded as function of incident proton position with a spatial resolution of 2 mu m. The CCE profile shows a broad plateau with CCE values close to 100% occurring at the depletion layer, whereas in the neutral region, the exponentially decreasing profile indicates the dominant role played by the diffusion transport mechanism. Mapping of charge pulses was accomplished by a novel computational approach, which consists in mapping the Gunn's weighting potential by solving the electrostatic problem by finite element method and hence evaluating the induced charge at the sensing electrode by a Monte Carlo method. The combination of these two computational methods enabled an exhaustive interpretation of the experimental profiles and allowed an accurate evaluation both of the electrical characteristics of the active region (e.g. electric field profiles) and of basic transport parameters (i.e. diffusion length and minority carrier lifetime). (C) 2011 Elsevier B.V. All rights reserved.
- ItemA Monte carlo software for the 1-dimensional simulation of IBIC experiments(Science Direct, 2014-08-01) Forneris, J; Jakšić, M; Pastuovic, Z; Vittone, EThe ion beam induced charge (IBIC) microscopy is a valuable tool for the analysis of the electronic properties of semiconductors. In this work, a recently developed Monte Carlo approach for the simulation of IBIC experiments is presented along with a self-standing software equipped with graphical user interface. The method is based on the probabilistic interpretation of the excess charge carrier continuity equations and it offers to the end-user the full control not only of the physical properties ruling the induced charge formation mechanism (i.e., mobility, lifetime, electrostatics, device’s geometry), but also of the relevant experimental conditions (ionization profiles, beam dispersion, electronic noise) affecting the measurement of the IBIC pulses. Moreover, the software implements a novel model for the quantitative evaluation of the radiation damage effects on the charge collection efficiency degradation of ion-beam-irradiated devices. The reliability of the model implementation is then validated against a benchmark IBIC experiment. © 2014, Elsevier B.V.
- ItemProbability of divacancy trap production in silicon diodes exposed to focused ion beam irradiation(American Institute of Physics, 2011-02-28) Pastuovic, Z; Vittone, E; Capan, I; Jakšić, MWe present ion beam induced charge (IBIC) measurements of the critical displacement damage dose D(d) values and modeling of the probability of divacancy trap production in p(+)-n-n(+) silicon diodes exposed to megaelectron volt energy ion beam irradiation. The normalized induced charge (Q(0)/Q) measured by He ion probe in tested silicon diodes irradiated by focused He, Li, O, and Cl ion beams with energies of about 0.3 MeV/u increases linearly with D(d) according to the modified radiation damage function and nonionizing energy loss (NIEL) theory. A simple IBIC model based on Gunn theorem showed clear dependence of the induced charge Q and corresponding equivalent damage factor Ked value on both a depth profile of charge created by ionizing particle (probe) and a depth distribution of stable defects created from primary defects produced by damaging ions. The average probability of the divacancy production (defined as the ratio of the final electrical active defect quantity and primary ion induced vacancy quantity for each impinging ion) of 0.18 (18%) was calculated by the IBIC modeling for all damaging ions. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559000]
- ItemRadiation hardness of n-type SiC Schottky diodes(Coop Libraria Editrice Universita di padova, 2014-07-07) Pastuovic, Z; Vittone, E; Siegele, R; Ohshima, T; Iwamoto, N; Forneris, J; Cohen, DD; Capan, IThe results of recent IBIC and DLTS studies of radation damage in silicon carbide (SiC) diodes will be presented. n-type Schottky diodes prepared on an epitaxial grown 4H-SiC thin wafers have been irradiated by a raster scanned alpha particle microbeam (2 & 4 MeV He2+ ions separately) in order to create patterned damage structures at different depths within sensitive volume of tested diodes suitable for Ion Beam Induced Current (IBIC) microscopy. Deep level transient spectroscopy (DLTS) was used to characterize defects created in SiC after implantation of single alpha particles. Robust and proven IBIC experimental protocol [1] has been used to determine a degradation of the charge collection efficiency over a wide fluence range of damaging alpha particle. The radiation hardness of these SiC wafers is compared with the hardness of n-type silicon wafers grown by the Floating zone and Czochralski methods obtained by the same experimental protocol. A suitability of as prepared SiC diodes for the light ion detection and spectroscopy in the MeV range will be discussed from the perspecetive of applications in harsh radiation environments.