arXiv subjects

Clóves Gonçalves Rodrigues

Publications and source records attributed to Clóves Gonçalves Rodrigues.

At least 19 recordsLinked to original sources

arXiv2023

Electronic Transport in the Silicon Carbide Semiconductor in Phase 3C

In this work we study, theoretically, electronic mobility of the silicon carbide semiconductor in the 3C phase, named 3C-SiC. 3C-SiC has shown great potential for applications in extreme conditions. Thus, the study of the electronic mobility of this semiconductor is of great interest. In this work were theoretically deduced: drift velocity, displacement and mobility of the charge carriers in the n-type doped 3C-SiC semiconductor, subjected to a constant electric field. The dependence of these transport properties as a function of the intensity of the electric field and temperature was analyzed. For this, a differential equation of motion was used with a source term (low intensity electric fields) and a term of resistance to movement (electrical resistance).

cond-mat.mtrl-sci↗

arXiv2022

The Relativistic Maxwell-Jüttner Velocity Distribution Function

In this paper, the expression of the relativistic Maxwell-Jüttner velocity distribution was deduced in a detailed and didactic way. This distribution was compared with the well-known Maxwell-Boltzmann distribution, which does not take into account relativistic effects. Applications and comparisons between the two distributions were carried out in three situations: i) protons at solar surface temperature, ii) electrons at Lawson's criterion temperature, and iii) protons at quasar temperatures. It was found that the value of the ratio between the rest mass of the particle considered and the temperature of the system determines the need to consider or not a relativistic treatment for the velocity distribution function of the system.

physics.gen-ph↗

arXiv2021

About the Evolution of the Concept of Heat and Thermal Energy

The concept of thermal energy was only fully formulated in the late 19th and early 20th centuries. The search for the understanding of calorific phenomena was what provided the construction and development of the concept of thermal energy. In this work we present the evolution of the concept of heat and thermal energy over time, following a chronological order and the evolution of the ideas and principles in question. For this, a vast bibliographical research on the subject was carried out. The theme has been addressed from the ancient Greek philosophers to the advent of modern physics with the elucidation of the phenomenon of thermal radiation.

physics.gen-ph↗

arXiv2021

Mobility in N-Doped Wurtzite III-Nitrides

A study of the mobility of n-doped wurtzite III-Nitrides is reported. We have determined the nonequilibrium thermodynamic state of the III-Nitrides systems, driven far away from equilibrium by a strong electric field, in the steady state, which follows after a very fast transient. The dependence of the mobility (which depends on the nonequilibrium thermodynamic state of the sample) on the electric field strength is derived, which decreases with the strength of electric field. We analyzed the contributions to the mobility arising out of the different channels of electron scattering, namely, the polar optic, deformation, piezoelectric, interactions with the phonons, and with impurities. The case of n-InN, n-GaN, and n-AlN have been analyzed: as expected the main contribution comes from the polar-optic interactions in these strongly polar semiconductors. The other interactions are in decreasing order, the deformation acoustic, the piezoelectric, and the one due to impurities.

cond-mat.mtrl-sci↗

arXiv2021

Hot Electron Dynamics in Zincblende and Wurtzite GaN

A theoretical investigation of the excess energy dissipation of highly excited photoinjected electrons in both wurtzite and zincblende GaN is presented. The calculations are performed by solving numerically coupled quantum transport equations for the carriers and the acoustic, transversal and longitudinal optical phonon in order to derive the evolution of their nonequilibrium temperatures, dubbed quasi-temperatures. It is shown that the electron energy dissipation is always faster in the wurtzite structure than in zincblende, both occurring in a subpicosecond time scale (< 0.2 ps).

cond-mat.mtrl-sci↗

arXiv2021

Intermolecular Correlations and Mean Square Relative Displacements in C60 Fullerite

We study molecular properties of the high-temperature modification of fullerites. In the present work we calculate the intermolecular correlations and the mean square relative displacements in C60. The Girifalco intermolecular potential is utilized. The calculations have been made in the whole interval from the equilibrium point with orientationally ordered phase up to the spinodal temperature. To take into account the lattice anharmonicity we use the correlative method of unsymmetrized self-consistent field. Its second order allows one to investigate correlations in FCC lattice between the nearest, second, third and fourth neighbors. The anharmonicity has strong effect on the intermolecular correlations at T>700 K, causing their drastic rise near the spinodal point. The dependence of the correlation moments on the distance between molecules and on the crystallographic direction is considered. We compare our results with those for solid Ar and discuss the influence of a special feature of the interaction potentials on the intermolecular correlations and the mean square molecular displacements.

cond-mat.mtrl-sci↗

arXiv2021

Topics in Present-Day Science Technology and Innovation: Ultrafast Relaxation Processes in Semiconductors

The nowadays notable development of all the modern technology, fundamental for the progress and well being of world society, imposes a great deal of stress in the realm of basic Physics, more precisely on Thermo-Mechanical Statistics. In electronics and optoelectronics we face situations involving physical-chemical systems far-removed-from equilibrium, where ultrafast (in pico- and femto-second scale) and non-linear processes are present. Here we describe in an extended overview the question of ultrafast relaxation processes in the excited plasma in semiconductors.

cond-mat.mtrl-sci↗

arXiv2021

Science, Technology and Non Equilibrium Statistical Mechanics

The binomial Science & Technology (S & T) is inseparable. In this contribution are presented some general considerations on the question of the aspect and interrelationships of the Science, Technology, Government and Society, and the role of Non Equilibrium Statistical Mechanics that are present in the nowadays highly sophisticated technologies and industrial processes that contribute to the wealth and well being of world society. The evolution of the Non Equilibrium Statistical Mechanics is briefly described. In present days remarkable development of all the modern technology, essential for the welfare and progress of the global society, imposes an immense stress on basic Physics, and consequently on Non Equilibrium Statistical Mechanics, in situations like, for example: fluids with complex structures, electronics and photonics involving systems out of equilibrium, nano-technologies, low-dimensional systems, non-linear and ultrafast processes in semiconductors devices, and soft matter. It is shown that the Non Equilibrium Statistical Mechanics can deal, within a certain degree of triumph, with some these situations, namely: 1. nonconventional thermo-hydrodynamics; 2. ultrafast relaxation processes in semiconductors devices; 3. nonequilibrium Bose-Einstein-like condensations and coherent states; 4. low-dimensional semiconductors; 5. thermo-statistics of complex structured systems; 6. nonlinear higher-order thermo-hydrodynamics; and 7. nonlinear transport in semiconductors devices. These areas are of particular interest, at the scientific, technological and at the production line, and therefore of relevance for government and society, successfully analyzed in terms of the formalism of Non Equilibrium Statistical Mechanics.

physics.soc-ph↗

arXiv2021

On a Possible Melting Curve of C60 Fullerite

We study the thermodynamic properties of the high-temperature modification of fullerites on the basis of the Girifalco intermolecular potential. In the present work, using Lindemann's melting criterion, we estimate a possible melting curve Tm(P) of C60 fullerite. To take into account the lattice anharmonicity, which has a strong effect at T > 700 K, we use the correlative method of unsymmetrized self-consistent field. To check this approach, first we have applied it to solid Ar. In the range between its triple point Tt = 83.807 K and 260 K we obtained the mean square relative deviation from experimental data of about 0.7%. The melting curve for C60 fullerite has been calculated from the melting point at normal pressure estimated at 1500 K up to 15 kbar, which corresponds to Tm = 4000 K, i.e. to the temperature estimated by Kim and Tománek [Phys. Rev. Lett. 72, 2418 (1994)] as that of the decomposition of the C60 molecule itself.

cond-mat.mtrl-sci↗

arXiv2021

Electron transport in GaN(ZB) and AlN(WZ)

Seeking a better understanding of the electron transport in n-doped zinc blende GaN and wurtzite AlN, it was performed here a theoretical study resorting to Non Equilibrium Statistical Operator Method, which provides a set of coupled nonlinear differential evolution equations that provides a description of the dissipative phenomena developed in the system. The ultrafast time evolution (and the steady-state) of the electron drift velocity is obtained assuming different values for the electron effective mass.

cond-mat.mtrl-sci↗

arXiv2021

Electron mobility in n-doped zinc sulphide

A study of the mobility of n-doped wurtzite and zincblende ZnS is reported. We have determined nonequilibrium thermodynamic state of the ZnS, driven far away from equilibrium by a strong electric field, in the steady state. The dependence of the mobility (which depends on the nonequilibrium thermodynamic state of the sample) on the electric field strength is derived, which decreases with the strength of electric field. We analyzed the contributions to the mobility arising out of the different channels of electron scattering, namely, the polar optic, deformation, interactions with the phonons, and with ionized impurities. The case of n-ZnS WZ and ZB have been analyzed: as expected the main contribution comes from the polar-optic interactions in this strong-polar semiconductor. The other interactions are in decreasing order, the deformation acoustic and the one due to impurities.

cond-mat.mtrl-sci↗

arXiv2021

Hot-Carrier Relaxation in Photoinjected ZnSe

A theoretical investigation of the excess energy dissipation of highly excited photoinjected carriers in zinc selenide (ZnSe) is presented. The calculations are performed by solving numerically coupled quantum transport equations for the carriers and the optical phonons in order to derive the evolution of their nonequilibrium temperatures, dubbed quasitemperatures (or nonequilibrium temperatures). It is shown that the carrier energy dissipation occurs in a picosecond time scale.

cond-mat.mtrl-sci↗

arXiv2021

Anisotropic Hole Drift Velocity in 4H-SiC

A theoretical study on the nonlinear transport of holes in the transient and steady state of p-doped 4H-SiC under the influence of high electric fields is presented. It is based on a nonlinear quantum kinetic theory which provides a clear description of the dissipative phenomena that are evolving in the system. The hole drift velocity and the nonequilibrium temperature are obtained, and their dependence on the electric field strength is derived and analyzed.

cond-mat.mtrl-sci↗

arXiv2021

Interatomic Correlations Moments of Atoms in the Two-Dimensional Hexagonal Lattice by Using Morse and Lenard-Jones Potentials

In this work we investigate the interatomic correlation moments in two-dimensional model of a weakly anharmonic crystal (i.e., not very high temperatures) with hexagonal lattice, using the Correlative Method of Unsymmetrized Self-Consistent Field (CUSF). The numerical results are obtained (and compared) by using the Morse and Lenard-Jones potentials.

cond-mat.mtrl-sci↗

arXiv2021

Anisotropic Carrier Transport in n-Doped 6H-SiC

In this paper, a study is presented on the charge transport in n-type doped semiconductor 6H-SiC (in both transient and steady state) using a nonequilibrium quantum kinetic theory derived from the method of nonequilibrium statistical operator (NSO), which furnishes a clear description of the irreversible phenomena that occur in the evolution of the analyzed system. We obtain theoretically the dependence on the electric field (applied in the orientation perpendicular or parallel to the c-axis) of the basic macrovariables: the electron drift velocity and the nonequilibrium temperature. The peak points in time evolution of this macrovariables are derived and analyzed.

cond-mat.mtrl-sci↗

arXiv2021

Nonlinear higher-order hydrodynamics: Fluids under driven flow and shear pressure

In the context of a nonequilibrium statistical thermodynamics, based on a nonequilibrium statistical ensemble formalism, a generalized hydrodynamics of fluids under driven flow and shear stress is derived. At the thermodynamic level, the nonequilibrium equations of state are derived, which are coupled to the evolution of the basic variables that describe the hydrodynamic motion in such a system. Generalized diffusion-advection and Maxwell-Cattaneo advection equations are obtained in appropriate limiting situations. This nonlinear higher-order hydrodynamics is applied, in an illustration, to the case of a dilute solution of Brownian particles in nonequilibrium conditions and flowing in a solvent acting as a thermal bath. This is done in the framework of such generalized hydrodynamics but truncated up to a second order.

cond-mat.stat-mech↗

arXiv2021

Electron Mobility in Bulk n-Doped SiC-Polytypes 3C-SiC, 4H-SiC, and 6H-SiC: A Comparison

This communication presents a comparative study on the charge transport (in transient and steady state) in bulk n-type doped SiC-polytypes: 3C-SiC, 4H-SiC and 6H-SiC. The time evolution of the basic macrovariables: the electron drift velocity and the non-equilibrium temperature are obtained theoretically by using a Non-Equilibrium Quantum Kinetic Theory, derived from the method of Nonequilibrium Statistical Operator (NSO). The dependence on the intensity and orientation of the applied electric field of this macrovariables and mobility are derived and analyzed. From the results obtained in this paper, the most attractive of these semiconductors for applications requiring greater electronic mobility is the polytype 4H-SiC with the electric field applied perpendicular to the c-axis.

cond-mat.mtrl-sci↗

arXiv2021

The Non-Equilibrium Statistical Operator Method

In this work we describe the Non-Equilibrium Statistical Operator Method (NESOM). The NESOM is a powerful formalism that seems to offer an elegant and concise way for an analytical treatment in the theory of irreversible processes, adequate to deal with a large class of experimental situations, and physically clear picture of irreversible processes. The method invented by D. N. Zubarev is also practical and efficient in the study of the optical and carrier dynamics in semiconductors. Keywords: nonequilibrium phenomena; kinetic theory; transport processes; irreversible processes.

physics.gen-ph↗