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Papers by Jose Fernando Diniz Chubaci

EPJ Web of Conferences

Boron-based thermal neutron detectors have recently regained some attention from the instrumentat... more Boron-based thermal neutron detectors have recently regained some attention from the instrumentation community as a strong alternative to helium-3 detectors. From the existing concepts exploiting boron layers in position sensitive detectors, the Cascade [1] is the one that takes full advantage of the 2D capabilities of gaseous detectors, with the position resolution not limited by the architecture of the detector. In this work, a proposal for the Cascade detector, based on Thick-GEMs is presented, together with some preliminary studies of the suitable pitch that optimizes the neutron conversion efficiency, while keeping the collection efficiency intact. The characterization of Thick-GEM prototypes produced in Brazil with hole pitch from 0.75 to 3 mm shows that these devices already present a stable performance at low gains, also resulting in fair energy resolution, when cascaded with a standard KaptonTM 50 µm GEM. Results of the first attempts of boron film depositions with Ion Beam...

Journal of Physics and Chemistry of Solids

Cienc. Cult. (Sao Paulo) Supl, 1982

Radiation Physics and Chemistry, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Crystal Growth, 2016

Abstract Density Functional Theory based on ab initio calculations was employed to investigate si... more Abstract Density Functional Theory based on ab initio calculations was employed to investigate single and complex defects of oxygen in indium nitride and their influence on the optical properties. Different oxygen contents (x=1.38%, 4.16%, 5.55% and 11.11%) were considered in our study by using PBEsol-GGA and TB-mBJ for the treatment of exchange-correlation energy and potential. It was found that oxygen is energetically favorable to exist mainly as singly charged isolated defect. The results using TB-mBJ approximation predicts a narrowing of the VBM (valence band maximum) and CBM (conduction band minimum) as oxygen content increases. Nevertheless, the larger contribution of the Moss-Burstein effect leads to an effective band-gap increase, yielding absorption edge values larger than that of the intrinsic bulk indium nitride.

Radiation Protection Dosimetry, 1993

Journal of Physics and Chemistry of Solids, 2016

A garnet (G7) silicate mineral belonging to pyralspite subgroup was studied using the technique o... more A garnet (G7) silicate mineral belonging to pyralspite subgroup was studied using the technique of electron spin resonance (ESR). This study shows that iron is present in G7 as isolated species as well as species coupled by dipolar interactions. The ESR data shows a gradual increase of cluster of Fe 3 þ ions accompanied by decrease of dipolar interactions and increase of possible exchange interactions at high temperature. The Fe 2 þ-Fe 3 þ oxidation process occurs in the garnets as a function of annealing temperature. Thermoluminescence (TL) peaks at approximately 190 and 340°C are observed in the irradiated G7 garnet. Investigations using the technique of ESR were carried out to identify the centers involved in the TL process.

2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)

Page 1. PURIFICATION AND PREPARATION OF TLBR CRYSTAL FOR ROOM TEMPERATURE RADIATION DETECTOR APPL... more Page 1. PURIFICATION AND PREPARATION OF TLBR CRYSTAL FOR ROOM TEMPERATURE RADIATION DETECTOR APPLICATIONS Icimone B. Oliveira, Fabio E. Costa, José FD Chubaci* and Margarida M. Hamada Abstract ...

MRS Proceedings, 2001

Fullerite nanotubules of 100 nm to 2 μm radius, up to 200 nm wal thickness and 10 μm length were ... more Fullerite nanotubules of 100 nm to 2 μm radius, up to 200 nm wal thickness and 10 μm length were produced inside etched swift heavy ion tracks in a polymer, by letting fullerence precipitate from a concentrated C60 solution within the tracks. After contacting the tubules on both sides with silver paste, their resistivity was measured as a function of temperature. All of the 13 prepared samples show a complex behaviour that can be described by tw Arrhenius curves, the low temperature branch with activation energy Eact = (1.77 ± 0.2) eV stemming from pure C60, and the high temperature branch being tentatively ascribed to C60Agx with x ≍ 12.4 and Eact = (0.68 ± 0.2) eV, as the letter compound has found to be produced at ambient temperature by C60 / Ag thermal intermixture. Such samples with tw branches of negative temperature coefficients of resistance might be useful to construct advanced thermoresistors.

ECS Transactions, 2010

The optical and electrical properties of nanostructured indium nitride (InN) thin films are studi... more The optical and electrical properties of nanostructured indium nitride (InN) thin films are studied in this work. Indium nitride films has been the subject of intensive research in the past few years due to its potential applications in optoelectronic area, such as solar cells and photo sensors. The primary objective of this work is to study the effects of deposition temperature on the crystallinity and morphology of these films. InN thin films were grown at room temperature (RT) and at 300 {degree sign}C using the Ion Beam Assisted Deposition (IBAD) method. The XRD patterns revealed that the room temperature deposited films were amorphous. Films formed at 300 {degree sign}C showed two peaks around 31{degree sign} (wurtzite-type InN 002) and around 33{degree sign} (metallic In 101). The thickness, roughness and deposition rate of the InN films were measured by high step meter and ellypsometer. In current versus voltage (IxV) analyses, all samples show semiconductor characteristics.

Radiation Protection Dosimetry, 1999

ABSTRACT Thermoluminescence (TL) intensity I(T), Q(T) and P(T) as a function of temperature T dur... more ABSTRACT Thermoluminescence (TL) intensity I(T), Q(T) and P(T) as a function of temperature T during glow curve readout are calculated numerically for three types of physical models, where Q(T) is called the quasi-equilibrium (QE) function and P(T) is the ratio of the retrapping to recombination rates. The models include a one trap-one recombination centre and an interactive or non-interactive deep trap. The results lead to the following conclusion: (1) Under a wide variety of parametric combinations Q(T) ( 1 and P(T) � 1 is a more common condition that Q(T) ( 1 and P(T) � 1. (2) Glow peaks with first order character are obtained even when P(T) � 1 which is contrary to the Randall and Wilkins Theory. These two conclusions are in clear contradiction to the assertions of Lewandowski and McKeever that Q(T) ( 1 and P(T) � 1 are not self-consistent conditions and that the dominance of first order TL kinetics in nature is explained only with P(T) � 1. This paper also discusses the practical side of the QE assumption in relation to the real materials and infers that the QE condition is most likely to prevail in the TL emission of common phosphors.