R. M. Rubinger

Universidade Federal de Itajubá

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G. M. Ribeiro

Universidade Federal de Minas Gerais

Adhimar Flávio Oliveira

Universidade Federal de Itajubá

Holokx A. Albuquerque

Universidade do Estado de Santa Catarina

A. G. de Oliveira

Universidade Federal de Minas Gerais

C. P. L. Rubinger

Universidade Federal de Itajubá

W. N. Rodrigues

Universidade Federal de Minas Gerais

M. V. B. Moreira

Universidade Federal de Minas Gerais

НА

Н. А. Соболев

University of Aveiro

João Ider

Universidade Federal de Itajubá

Vander Alkmin dos Santos Ribeiro

Universidade Federal de Itajubá

Cooperative Institutions

Universidade Federal de Itajubá

Universidade Federal de Minas Gerais

University of Aveiro

Universidade de São Paulo

Universidade Estadual de Campinas (UNICAMP)

Centre National de la Recherche Scientifique

École Polytechnique Fédérale de Lausanne

Universidade Federal de São Carlos

Russian Academy of Sciences

Universidade do Porto

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Experimental study of negative differential conductivity in GaAs:Cr

Physical review. B, Condensed matter (2000)

R. M. Rubinger A. G. de Oliveira J. C. Bezerra G. M. Ribeiro W. N. Rodrigues

We have studied the temperature and illumination dependencies of the current versus voltage characteristics $I(V)$ of a Cr-doped GaAs sample. An S-shaped negative differential conductivity with a threshold at around 1 kV ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ was associated with a trap with activation energy of 90 meV. The low-conductivity state in $I(V)$ characteristics is strongly influenced by illumination and temperature. We also present evidence that the electrical conduction above the threshold electric field occurs by a mechanism that involves free electrons despite the fact that the low-conductivity state is p type. This supports the assumption that the 90 meV trap is a donor.

10.1103/physrevb.62.1859

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Citations (7)

Hopping conduction on carbon black/styrene–butadiene–styrene composites

Journal of Materials Science (2011)

C. P. L. Rubinger María Elena Leyva Bluma G. Soares G. M. Ribeiro R. M. Rubinger

Styrene-butadiene

Carbon fibers

Variable-range hopping

10.1007/s10853-011-5864-2

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Citations (11)

Preparation and characterization of palladium-doped titanium dioxide for solar cell applications

Materials Science and Engineering B (2022)

Adhimar Flávio Oliveira S.A.M. Silva C. P. L. Rubinger João Ider R. M. Rubinger

Brookite

Titanium Dioxide

Energy-dispersive X-ray spectroscopy

10.1016/j.mseb.2022.115702

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Citations (4)

Impacts of temperature and irradiance on polycrystalline silicon solar cells parameters

Solar Energy (2018)

Davi Fébba R. M. Rubinger Adhimar Flávio Oliveira Edson C. Bortoni

Equivalent series resistance

Saturation current

Polycrystalline silicon

10.1016/j.solener.2018.09.051

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Citations (71)

Determination of thickness and refractive index of SiO2 thin films using the cross-entropy global optimization method

Research Society and Development (2021)

Sávio José Vieira Zaccaro Adhimar Flávio Oliveira R. M. Rubinger Crediana Chris de Siqueira Roberto Affonso da Costa

Silicon dioxide (SiO2) is a material that is abundant in nature and has wide application in semiconductor and insulating devices. In this work, a set of six SiO2 samples were grown on a Sigma-Aldrich Silicon substrate, varying the growth time and temperature. This set of samples were grown using times of 10 and 12h and temperatures of 800, 900, and 1000 ºC, under ambient atmosphere. After film growth, reflectance measurements were performed on the films and the substrate, using the Stellarnet UV-VIS-NIR spectrophotometer between 194 and 1081.5 nm. These measurements were modeled using a global optimization method, called Cross-entropy, together with the Bootstrapping resampling technique, seeking to robustly and statistically determine the thin film refractive index as a function of the wavelength and its thickness. To estimate the refractive index of the SiO2 thin film, the Cauchy model was used. For the substrate, reflectance measurements were used. The method proved to be efficient, presenting thickness values that were validated according to growth parameters and literature data. This method proved to be an important and low-cost tool, compared to traditional methods, to help in the steps of building thin films for semiconductor and insulating devices, thus improving their physical properties and enabling the development of new devices.

10.33448/rsd-v10i10.19028

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Citations (5)

Reduction of variable range hopping conduction in low-temperature molecular-beam epitaxy GaAs

Journal of Applied Physics (2004)

Holokx A. Albuquerque A. G. de Oliveira G. M. Ribeiro R. L. da Silva W. N. Rodrigues

Studying the transport properties via Hall and resistivity measurements of low-temperature molecular-beam epitaxy (LT-MBE) GaAs samples, the optimal conditions for fabricating high-resistivity material are found. We present results on three LT-MBE GaAs samples grown at 215, 265, and 315 °C. The measurements were carried out at temperatures ranging from 130 to 300 K, and the hopping conduction mechanism in this range is identified as variable range hopping. The sample grown at 315 °C presents the highest hopping parameter; this appears to be due to a reduction in the density of hopping centers. The mechanisms responsible for this are discussed.

Variable-range hopping

Atmospheric temperature range

10.1063/1.1650530

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Citations (5)

Dielectric properties of ternary melt processed blends

Journal of Non-Crystalline Solids (2008)

Cristiane Reis Martins C. P. L. Rubinger L.C. Costa R. M. Rubinger

10.1016/j.jnoncrysol.2008.05.070

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Citations (3)

Nonlinear dynamics time series analysis of chaotic current oscillations in a semi-insulating GaAs sample

Brazilian Journal of Physics (2002)

R.L. da Silva R. M. Rubinger A. G. de Oliveira G. M. Ribeiro

We have carried out our experiments on a semi-insulating GaAs sample grown by low temperature Molecular Beam Epitaxy. Three parameters were used to fine tune the experiments, namely, temperature, illumination, and applied bias. We have used powerful tools of time series analysis in order to assess the embedding dimension through near false nearest neighbors. We have also measured the maximum Lyapunov exponent and the correlation dimension [1]. The main contribution was in presenting new experimental data and its analysis which presents self-generated chaos.

Correlation dimension

Sample (material)

Exponent

10.1590/s0103-97332002000200047

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Citations (2)

Dielectric properties of PANI/PSS blends obtained by in situ polymerization technique

Polymer Bulletin (2007)

C. P. L. Rubinger Roselena Faez L.C. Costa Cristiane Reis Martins R. M. Rubinger

Polystyrene

Sulfonic acid

In situ polymerization

10.1007/s00289-007-0868-4

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Citations (8)

Impurity breakdown in GaAs samples grown by molecular beam Epitaxy

Brazilian Journal of Physics (1999)

R. M. Rubinger Admilton Gonçalves de Oliveira G. M. Ribeiro J. C. Bezerra C.M. Silva

In this work we present studies for the behavior of impurity breakdown of two GaAs samples grown by Molecular Beam Epitaxy at 200°C and 300°C. We vary the temperature and the illumination intensity. For the sample grown at 200°C, the transport mechanism after the breakdown is of the same type of the main free carriers at low electric fields. Below 100K, a clear dependence of the threshold electric field with temperature was observed. The sample grown at 300°C shows a breakdown due to an acceptor level at 41meV from the valence band. The threshold electric field increases with illumination due to the generation of free electrons by deep levels. A similar behavior was also observed for a Cr doped GaAs sample.

Acceptor

10.1590/s0103-97331999000400038

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Citations (0)