International Journal of Physics | Vol. 9, No. 6, June 2018 | pp. 41–48
DOI: 10.46882/2018/IJP/000098
Research Article
Title: Kinetic Simulation of Electron Transport Properties and Radical Yields in Nitrogen-Trifluoride Discharges
Names of Authors: A. M. El-Chemali¹, S. H. Zhang²
Authors’ Affiliations: ¹Department of Physics, Faculty of Science, Lebanese University, Beirut, Lebanon; ²Department of Physics, Tsinghua University, Beijing, China
Abstract: Nitrogen trifluoride (NF3) gas discharges are widely utilized in plasma processing reactors for chamber cleaning and silicon nitride thin-film etching. This study develops a self-consistent kinetic simulation model to analyze electron transport properties and compute radical generation rates in low-pressure NF3 discharges. We solved the electron Boltzmann equation using a multi-term spherical harmonic expansion scheme across a reduced electric field range (E/N) from 10.0 Td to 600.0 Td. The model incorporates comprehensive cross-section sets, including elastic scattering, vibrational excitation, dissociative attachment, and direct impact ionization processes. Our modeling results show that adding nitrogen diluents (from 10.0% to 50.0% by volume) drastically distorts the electron energy distribution function. At a field strength of E/N = 80.0 Td, the total fluorine radical production rate coefficient increases by over an order of magnitude due to shifting electron mean energies. This enhancement accelerates chemical etching paths during processing. The calculated electron drift velocities and longitudinal diffusion coefficients match independent swarm experimental measurements within a ±4.5% variance. These kinetic parameters provide essential baseline input data for optimizing industrial semiconductor chamber performance.
Keywords: Nitrogen trifluoride; Boltzmann equation; electron transport; plasma kinetics; cross-section; semiconductor etching
Manuscript Timeline: Received: February 15, 2018; Revised: April 12, 2018; Accepted: May 04, 2018; Published: June 15, 2018
Citation: El-Chemali, A. M., & Zhang, S. H. (2018). Kinetic Simulation of Electron Transport Properties and Radical Yields in Nitrogen-Trifluoride Discharges. International Journal of Physics, 9(6), 41–48.
International Journal of Physics | Vol. 9, No. 5, May 2018 | pp. 33–40
DOI: 10.46882/2018/IJP/000097
Research Article
Title: High-Pressure Elastic Moduli and Mechanical Stability of Ultra-Incompressible Molybdenum Tetraboride
Names of Authors: V. I. Morozov¹, I. R. Sokolov²
Authors’ Affiliations: ¹Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia; ²Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia
Abstract: Designing ultra-incompressible structural materials capable of withstanding extreme mechanical stress is vital for industrial tooling and high-pressure research components. This paper examines the high-pressure elastic moduli and structural stability of orthorhombic molybdenum tetraboride (MoB4) up to hydrostatic pressures of 140.0 GPa. We performed first-principles density functional theory computations within the generalized gradient approximation framework. At zero pressure, the calculated bulk modulus is B0 = 312.0 GPa, with an elastic derivative value of B0' = 4.18. These results match experimental diamond anvil cell measurements within a 1.5% margin. The single-crystal elastic constants (C11, C22, C33, C44, C55, and C66) increase monotonically under compression, satisfying all Born mechanical stability conditions across the tested pressure range. The directional compressibility curves reveal that the crystal c-axis is significantly stiffer than the a-axis and b-axis, which is due to short, covalent molybdenum-boron bonds aligned along the plane. The electronic structure calculations show a high density of states at the Fermi level, indicating that MoB4 retains its metallic character under high pressure. These precise elastic profiles confirm the potential of transition metal borides as viable alternatives to diamond-based superhard materials.
Keywords: Molybdenum tetraboride; density functional theory; elastic constants; high pressure; mechanical stability; directional compressibility
Manuscript Timeline: Received: January 20, 2018; Revised: March 05, 2018; Accepted: April 02, 2018; Published: May 11, 2018
Citation: Morozov, V. I., & Sokolov, I. R. (2018). High-Pressure Elastic Moduli and Mechanical Stability of Ultra-Incompressible Molybdenum Tetraboride. International Journal of Physics, 9(5), 33–40.
International Journal of Physics | Vol. 9, No. 4, April 2018 | pp. 25–32
DOI: 10.46882/2018/IJP/000096
Research Article
Title: Resonant Energy Transfer Dynamics between Colloidal PbS Quantum Dots and Monolayer Tungsten Disulfide
Names of Authors: T. H. Nguyen¹, M. G. Richter²
Authors’ Affiliations: ¹Department of Physics, Vietnam National University, Hanoi, Vietnam; ²Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
Abstract: Hybrid semiconductor nanostructures combining zero-dimensional quantum dots and two-dimensional layers provide new opportunities for developing advanced light-harvesting systems. This paper examines the non-radiative Förster resonant energy transfer (FRET) dynamics between colloidal lead sulfide (PbS) quantum dots and monolayer tungsten disulfide (WS²). The hybrid interfaces were fabricated via sequential spin-coating routines onto quartz substrates. We performed steady-state photoluminescence and time-resolved single-photon counting measurements at an operating temperature of 300 K. The experimental data reveal a strong 85.0% quenching of the quantum dot photoluminescence emission when coupled to the WS² monolayer. Concurrently, the average fluorescence lifetime of the PbS quantum dots decreased from 5.4 ns down to 0.81 ns. This lifetime reduction yields a calculated FRET efficiency of 85.0% with a corresponding energy transfer rate of 1.05 ns⁻¹. The donor-acceptor separation distance was estimated to be 3.5 nm using the standard Förster mathematical model. Spectral overlap analysis confirms that energy transfer is mediated by the alignment between quantum dot emission and the WS² exciton absorption bands. These rapid energy transfer dynamics show that quantum dot sensitization can significantly enhance near-infrared light absorption in ultra-thin optoelectronic architectures.
Keywords: Quantum dots; transition metal dichalcogenides; resonant energy transfer; fluorescence lifetime; hybrid nanostructures; optoelectronics
Manuscript Timeline: Received: January 04, 2018; Revised: February 17, 2018; Accepted: March 09, 2018; Published: April 11, 2018
Citation: Nguyen, T. H., & Richter, M. G. (2018). Resonant Energy Transfer Dynamics between Colloidal PbS Quantum Dots and Monolayer Tungsten Disulfide. International Journal of Physics, 9(4), 25–32.
International Journal of Physics | Vol. 9, No. 3, March 2018 | pp. 17–24
DOI: 10.46882/2018/IJP/000095
Research Article
Title: Density Functional Theory Analysis of Catalytic Oxygen Evolution on Nitrogen-Doped Graphene Nanoribbons
Names of Authors: A. L. Silva¹, H. L. Mueller²
Authors’ Affiliations: ¹Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; ²Institut für Kernphysik, Karlsruher Institut für Technologie, Karlsruhe, Germany
Abstract: The electrochemical oxygen evolution reaction (OER) is essential for chemical solar energy conversion and modern water-splitting technologies. This investigation uses density functional theory calculations to analyze the catalytic performance and reaction mechanisms of oxygen evolution on nitrogen-doped graphene nanoribbons. We modeled three distinct configurations: edge pyridinic, center pyrrolic, and quaternary nitrogen doping patterns. Free energy profiles for intermediate steps leading to molecular oxygen (*OH, *O, and *OOH) were computed using the computational hydrogen electrode model. The calculations demonstrate that edge pyridinic nitrogen sites lower the activation barrier for the rate-determining step (*O -> *OOH) to 0.48 eV. This value is significantly lower than the 1.25 eV barrier calculated for pristine carbon surfaces. The overpotential required to trigger selective oxygen evolution on pyridinic configurations was estimated at -0.42 V versus the standard hydrogen electrode. Charge density difference mappings show that nitrogen doping induces localized spin polarization and electron deficiency on adjacent carbon atoms. This electronic reconfiguration stabilizes the adsorbed intermediates. These quantum mechanical insights provide theoretical guidelines for developing metal-free, carbon-based catalysts for efficient solar fuel production plants.
Keywords: Oxygen evolution reaction; density functional theory; nitrogen-doped graphene; electrocatalysis; reaction mechanism; overpotential
Manuscript Timeline: Received: December 10, 2017; Revised: January 20, 2018; Accepted: February 08, 2018; Published: March 14, 2018
Citation: Silva, A. L., & Mueller, H. L. (2018). Density Functional Theory Analysis of Catalytic Oxygen Evolution on Nitrogen-Doped Graphene Nanoribbons. International Journal of Physics, 9(3), 17–24.
International Journal of Physics | Vol. 9, No. 2, February 2018 | pp. 9–16
DOI: 10.46882/2018/IJP/000094
Research Article
Title: Finite Element Modeling of Acoustic Wave Scattering and Bandgap Formations in Porous Piezoceramic Metamaterials
Names of Authors: P. J. O’Connor¹, V. I. Morozov²
Authors’ Affiliations: ¹Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland; ²Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia
Abstract: Characterizing elastic wave propagation through fluid-saturated porous structures is crucial for industrial noise mitigation and optimizing tunable smart structural systems. This study presents a finite element modeling approach to simulate acoustic wave scattering and track bandgap formations within a saturated porous piezoceramic metamaterial matrix. The mathematical model integrates Biot's dynamic equations of poroelasticity with a generalized piezoelectric constitutive framework to account for electro-mechanical coupling under variable external electrical shunting networks. Numerical simulations were executed across an ultrasonic frequency spectrum from 20.0 kHz to 600.0 kHz. The computational results demonstrate that introducing active inductive-capacitive shunts induces a strong, tunable attenuation peak for the fast compressional wave mode at 210.0 kHz. This attenuation can be actively shifted by 35.0% across the frequency domain via external load tuning. The scattering cross-section displays a non-linear dependence on core porosity fractions, showing optimal bandgap breadth below a 22.0% threshold. Experimental validation was conducted using synthetic barium titanate porous specimens filled with matching viscoelastic liners. The measured transmission loss spectra matched the simulated profiles within a ±5.5% margin.
Keywords: Porous media; acoustic scattering; piezoceramics; finite element modeling; Biot's theory; tunable bandgaps
Manuscript Timeline: Received: November 02, 2017; Revised: December 18, 2017; Accepted: January 11, 2018; Published: February 14, 2018
Citation: O’Connor, P. J., & Morozov, V. I. (2018). Finite Element Modeling of Acoustic Wave Scattering and Bandgap Formations in Porous Piezoceramic Metamaterials. International Journal of Physics, 9(2), 9–16.
International Journal of Physics | Vol. 9, No. 1, January 2018 | pp. 1–8
DOI: 10.46882/2018/IJP/000093
Research Article
Title: Fluid Velocity Mapping and Flare Energetics in Solar Coronal Holes via Space-Based Extreme Ultraviolet Diagnostics
Names of Authors: G. R. Davies¹, A. M. El-Chemali²
Authors’ Affiliations: ¹School of Physics and Astronomy, University of St Andrews, St Andrews, UK; ²Department of Physics, Faculty of Science, Lebanese University, Beirut, Lebanon
Abstract: Magnetic reconnection is the primary physical process driving explosive energy releases in solar atmospheric plasma, heating material to millions of Kelvin and accelerating the fast solar wind. This paper evaluates fluid velocity mapping and quantifies local magnetic reconnection rates within an active coronal hole boundary region. We utilized high-resolution spectroscopic data from space-based extreme ultraviolet (EUV) channels tracking highly ionized iron lines (Fe XII and Fe XV). Differential affine velocity estimator algorithms were deployed to construct two-dimensional velocity fields of plasma inflows and outflows surrounding the current sheet layer. The empirical measurements reveal systematic plasma inflows moving at 20.5 km/s, while directed outflows reach velocities of 340.0 km/s along the magnetic open field corridors. Based on these transport metrics, the local dimensionless reconnection rate was calculated to range between 0.06 and 0.09. These values closely match fast reconnection regimes predicted by the Petschek theoretical framework modified by localized turbulent transport. Spectroscopic line-broadening analysis indicates localized turbulent temperatures peaking at 8.8 MK within the diffusion region, confirming intense localized viscous dissipation. These imaging diagnostics provide direct observational parameters for refining magnetohydrodynamic models of high-speed solar wind acceleration.
Keywords: Solar corona; coronal holes; magnetic reconnection; plasma dynamics; solar wind; extreme ultraviolet
Manuscript Timeline: Received: October 12, 2017; Revised: November 24, 2017; Accepted: December 15, 2017; Published: January 15, 2018
Citation: Davies, G. R., & El-Chemali, A. M. (2018). Fluid Velocity Mapping and Flare Energetics in Solar Coronal Holes via Space-Based Extreme Ultraviolet Diagnostics. International Journal of Physics, 9(1), 1–8.