Investigation of the role of defects on channel density profiles and their effect on the output characteristics of a nanowire FET

This work investigates the effect of defects on the electron density profiles of nanowire FETs with a rectangular cross-section. It also presents a framework for the discretization of the nanowire channels with defects. A self-consistent procedure using Schrodinger-Poisson solver with density matrix formalism calculates the local electron density profiles. The local electron density decreases due to defect-induced scattering potentials. The electron density profiles vary according to the nature of the intrinsic defects. The effect of defect-induced potentials on the output characteristics of the nanowire FET device is studied using the non-equilibrium Green's function (NEGF) methodology. An increase in scattering potential in the nanowire channel causes a considerable decrease in the saturation voltage and current. This results in a faster saturation which changes the overall device performance. Hence, defect-controlled channels can be utilized to fabricate FETs with desired characteristics.

Effect of magnetic field, size and donor position on the absorption coefficients related a donor within the core/shell/shell quantum dot

In this study, linear, nonlinear and total optical absorption coefficients related a single shallow donor atom confined in semiconductor core/shell/shell quantum dot heterostructure are researched in detail within the compact density matrix formalism approximation. For this purpose, firstly, the energies and the wavefunctions are computed by the diagonalization method in the effective mass approach. Moreover, the effects of size modulation, donor position and magnetic field are analyzed. The numerical results indicate that the linear and nonlinear parts of the absorption coefficients related with intersubband 1s-1p and 1p-1d donor transitions undergo significant changes.

Laser isotope separation of 176Lu through off-the-shelf lasers

We propose a novel and simple method for the laser isotope separation of 176Lu a precursor for the production of 177Lu medical isotope. The physics of the laser-atom interaction has been studied through the dynamics of the atomic level populations using the density matrix formalism. It has been shown that a combination of cw excitation lasers and pulsed ionization laser can be used for the laser isotope separation of 176Lu. The optimum conditions for the efficient and selective separation of 176Lu have been derived by studying the time evolution of level population under laser excitation. It has also been shown that, it might be possible to produce ~ 100% enriched 176Lu isotope at a rate of 5 mg/h, which is higher than all previously reported methods so far. The isotope separation process proposed can be easily adopted using off-the-shelf lasers, for similar atomic systems.

Derivation of the stationary fluorescence spectrum formula for molecular systems from the perspective of quantum electrodynamics

Numerical simulations of stationary fluorescence spectra of molecular systems usually rely on the relation between the photon emission rate and the system’s dipole–dipole correlation function. However, research papers usually take this relation for granted, and standard textbook expositions of the theory of fluorescence spectra also tend to leave out this important relation. In order to help researchers with less theoretical training gain a deeper understanding of the emission process, we perform a step-by-step derivation of the expression for the fluorescence spectrum, focusing on rigorous mathematical treatment and the underlying physical content. Right from the start, we employ quantum description of the electromagnetic field, which provides a clear picture of emission that goes beyond the phenomenological treatment in terms of the Einstein A coefficient. Having obtained the final expression, we discuss the relation of the latter to the present level of theory by studying a simple two-level system. From the technical perspective, the present work also aims at familiarizing the reader with the density matrix formalism and with the application of the double-sided Feynman diagrams.

Laser isotope separation of 176Lu through off-the-shelf lasers

We propose a novel and simple method for the laser isotope separation of 176Lu a precursor for the production of177Lu medical isotope. The physics of the laser-atom interaction has been studied through the dynamics of the atomic level populations using the density matrix formalism. It has been shown that a combination of cw excitation lasers and pulsed ionization laser can be used for the laser isotope separation of 176Lu. The optimum conditions for the efficient and selective separation of 176Lu have been derived by studying the time evolution of level population under laser excitation. It has also been shown that, it is possible to produce ~100% enriched 176Lu isotope at a rate of 5 mg / hour, which is higher than all previously reported methods so far. The isotope separation process proposed can be easily adopted using off-the-shelf lasers, for similar atomic systems.

Laser isotope separation of 176Lu through off-the-shelf lasers

We propose a novel and simple method for the laser isotope separation of 176Lu a precursor for the production of177Lu medical isotope. The physics of the laser-atom interaction has been studied through the dynamics of the atomic level populations using the density matrix formalism. It has been shown that a combination of cw excitation lasers and pulsed ionization laser can be used for the laser isotope separation of 176Lu. The optimum conditions for the efficient and selective separation of 176Lu have been derived by studying the time evolution of level population under laser excitation. It has also been shown that, it is possible to produce ~100% enriched 176Lu isotope at a rate of 5 mg / hour, which is higher than all previously reported methods so far. The isotope separation process proposed can be easily adopted using off-the-shelf lasers, for similar atomic systems.

Optical properties of two-dimensional two-electron quantum dot in parabolic confinement

The Hamiltonian and wavefunctions of two-dimensional two-electron quantum dots (2D2eQD) in parabolic confinement are determined. The ground and excited state energies are calculated solving the Schrödinger equation analytically and numerically. To determine the energy eigen-value of the system variational method is employed due to the large coupling constant λ ≈ 1.1 \lambda \approx 1.1 . The trial wavefunctions are developed for both ground and excited states. The ground state wave function is a para state and the excited state wavefunctions belong to both para and ortho states based on the symmetry and antisymmetry of spatial wavefunctions. Using the obtained energy eigen-values at the two states, the first- and third-order nonlinear absorption coefficient and refractive index are analytically obtained with the help of density matrix formalism and iterative procedure.