A5024735145- Diamond and Carbon-based Materials Research
- Molecular Junctions and Nanostructures
- High-pressure geophysics and materials
- Quantum and electron transport phenomena
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Boron and Carbon Nanomaterials Research
- Metal and Thin Film Mechanics
- Educational and Social Studies
- ZnO doping and properties
- Synthesis and Properties of Aromatic Compounds
- Advancements in Battery Materials
- Semiconductor materials and devices
- Surface and Thin Film Phenomena
- Electrocatalysts for Energy Conversion
- Electrochemical Analysis and Applications
- Rare-earth and actinide compounds
- Topological Materials and Phenomena
- Force Microscopy Techniques and Applications
- Graphite, nuclear technology, radiation studies
- GaN-based semiconductor devices and materials
- Autism Spectrum Disorder Research
- Management, Economics, and Public Policy
- Magnetic properties of thin films
- Historical and Environmental Studies
University of South Africa
2011-2024
Spin-orbit coupling gives rise to a range of spin-charge interconversion phenomena in nonmagnetic systems where certain spatial symmetries are reduced or absent. Chirality-induced spin-selectivity (CISS), term that generically refers spin-dependent electron transfer chiral systems, is one such case, appearing variety seemingly unrelated situations ranging from inorganic materials molecular devices. In particular, the origin CISS junctions matter an intense current debate. Here, we derive set...
We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during stretching a single molecule junction due to stapling both ends inner helix. In reported compounds, different conductive pathways are observed, clearly conductance values and plateau-length distributions, attributed conformations helical structures. The large chiro-optical responses potential use these molecules as unimolecular spin filters have been...
The production of $n$-type doped diamond has proved very difficult. Phosphorus, and possibly sulfur, when in substitutional sites the lattice, forms a donor which could be used electronic devices. Boron, is relatively shallow acceptor, can passivated by hydrogen, it possible that some difficulties producing electrically active donors due to their passivation hydrogen present during chemical vapor deposition growth diamond. We report ab initio modeling these dopants complexes with show...
We present ab initio full-potential density functional calculations of the electronic structure ${\mathrm{Ti}}_{0.0625}{\mathrm{Zn}}_{0.9375}\mathrm{O}$. show that it is likely for Ti to order ferromagnetically in $\mathrm{ZnO}$, forming a dilute magnetic semiconductor, agreement with experiment. The ferromagnetic ordering occurs despite being nonmagnetic its natural phase. ${\mathrm{Ti}}_{0.0625}{\mathrm{Zn}}_{0.9375}\mathrm{O}$ shown possess moment $0.63{\ensuremath{\mu}}_{B}$ per...
The single substitutional nitrogen atom in diamond is apparently a very simple defect elemental solid. It has been modelled by range of computational models, few which either agree with each other, or the experimental data on defect. If models less well understood defects this and more complex materials are to be reliable, we should understand why discrepancies arise how they can avoided future modelling. This paper presents an all-electron, augmented plane-wave (APW) density functional...
It is shown that a $4d$ metal (palladium) orders ferromagnetically in GaN, forming dilute magnetic semiconductor. The ferromagnetic ordering occurs despite Pd being nonmagnetic its natural phase. ${\mathrm{Pd}}_{0.0625}{\mathrm{Ga}}_{0.9375}\mathrm{N}$ to possess moment of $1.3\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}$ per supercell, with spin-polarized impurity band the GaN gap and Fermi level lying within this band. arise from hybridization N $2p$ states. Though largest...
Helical molecules have been proposed as candidates for producing spin-polarized currents, even at room conditions, due to their chiral asymmetry. However, describing transport mechanism in single molecular junctions is not straightforward. In this work, we show the synthesis of two novel kinds dithia[11]helicenes study electronic break among a series three helical molecules: dithia[
The spin and lattice dynamics of a ferromagnetic nanoparticle are studied via molecular with semi-classical simulations where degrees freedom coupled dynamic uniaxial anisotropy term. We show that this model conserves total angular momentum, whereas momentum not conserved. carry out the Einstein–de Haas effect for Fe nanocluster more than 500 atoms is free to rotate, using modified version open-source spin-lattice code (SPILADY). rate transfer between proportional strength magnetic...
Interstitial lithium and sodium have been suggested as alternatives to phosphorus achieve shallow $n$-type doping of diamond. Experimental results have, however, contradictory. We report ab initio density functional theory modeling in diamond show that although interstitial Li Na are likely behave donors, will readily diffuse with a low activation energy it is energetically favorable for both species be trapped at existing vacancies The resulting substitutional centers themselves not only...
Our analysis of the contact formation processes undergone by Au, Ag and Cu nanojunctions, reveals that distance at which two closest atoms on a pair opposing electrodes jump into is, average, times longer for Au than either or Cu. This suggests existence range interaction between those in case result significant relativistic energy contributions to electronic structure this metal, as confirmed ab initio calculations. Once regime, differences are subtle, conductance single-atom contacts...
Using the density-functional theory approach, including Hubbard U correction, we investigate defect structures consisting of vanadium (V) atoms embedded in a monolayer silicene. Specifically, consider V–V atom pairs antiferromagnetic (AFM), ferromagnetic (FM), and non-magnetic states, which are substitutional interstitial sites. We determine ground-state structures, formation binding energies, electronic induced magnetization, as well spin-exchange coupling between pair. For pair, stability...
We report ab initio pseudopotential DFT calculations on the energetic stability and magnetic ordering of Cr in diamond at various lattice sites charge states show that is most stable divacancy site diamond, with lowest formation energy occurring $n$- or $p$-type compared to intrinsic diamond. The incorporation introduces strongly spin polarized impurity bands into band gap, both polarization stabilization energies critically dependent state position Fermi level In we predict Cr${}^{+2}$...
Half-metallic ferromagnetic ordering in semiconductors, essential the emerging field of spintronics for injection and transport highly spin polarised currents, has up to now been considered mainly III–V II–VI materials. However, low Curie temperatures have limited implementation room temperature device applications. We report ab initio Density Functional Theory calculations on properties Fe diamond, considering effects lattice site, charge state, Fermi level position. show that sites induced...
The origin of high Curie temperature ferromagnetism in dilute magnetic semiconductors and oxides has often been attributed to clustering crystallographic phase separation atoms, which may have a detrimental impact on the properties host material for target applications. We present Density Functional Theory calculations stability interactions embedded Fe+1 ions diamond by considering various possible cluster configurations. find that Fe strong tendency form clusters diamond, with larger sizes...
Abstract We report on the chemical design of chiral molecular junctions with stress‐dependent conductance, whose helicity is maintained during stretching a single molecule junction due to stapling both ends inner helix. In reported compounds, different conductive pathways are observed, clearly conductance values and plateau‐length distributions, attributed conformations helical structures. The large chiro‐optical responses potential use these molecules as unimolecular spin filters have been...
In the field of molecular electronics, especially in quantum transport experiments, determining geometrical configurations a single molecule trapped between two electrodes can be challenging. To address this challenge, we employed combination dynamics (MD) simulations and electronic calculations based on density functional theory to determine orientation our break-junction experiments under ambient conditions. The molecules used study are common solvents such as benzene, toluene (aromatic),...
We present a first principles study of Cu in diamond using DFT+U electronic structure methods, by carefully considering the impact co-doping, charge state, and Fermi level position on its stability, lattice location, spin states, properties. show that energetic stability states are strongly dependent type with being energetically more favorable n-type or p-type co-doped compared to intrinsic diamond. Since has been predicted order magnetically number other wide band-gap semiconductors, we...
Abstract Spin-charge inter-conversion mediated by spin-orbit coupling can lead to finite magnetoconductance in two-terminal molecular nanojunctions under non-equilibrium conditions. Here, we demonstrate how such a emerge model means of density functional theory based transport calculations with first-order perturbation approximation. The junctions are built from the two chiral partners an idealized helical molecule and tungsten or gold electrodes layers magnetic nickel at interface drain...