Papers by Keyword: Potential Barrier

Abstract: In this paper, an analytical expression of the electron spin-dependent tunneling current through a potential barrier by applying a bias voltage was investigated. An Airy wavefunction was applied to derive the transmittance through the barrier by considering a zinc-blende material, which depends on the spin states indicated as ‘up’ and ‘down’. The obtained transmittance was employed to compute the polarization and spin-dependent tunneling current. The spin-dependent tunneling current was then observed at various bias voltages and temperatures. It was shown that the spin-polarized current increases as the bias voltage increases. It was also shown that the increase of temperature enhances the spin-dependent tunneling current.

Abstract: In this paper we have considered two versions of elementary cells for creating a nanomembrane, which will be used to separate natural gas into different gas components. Calculated trajectories of helium atoms and methane molecules interacting with elementary structural units of the membrane are presented. The model is based on a discrete approach to describe the interaction of a structure with atoms and molecules.

Abstract: In the framework of the generalized Kramers theory of physical and chemical kinetics the relation for the decay rate of the metastable state is obtained. The peculiarity of the system is the ratio of the potential barrier height to temperature of the system. This ratio is much less than unity. To study the process we introduce the concept of the effective square of the potential barrier. It is shown that in the limiting case the obtained relation becomes the standard formula (Kramers formula) for the decay rate.

Abstract: The choice of materials and the design of device structure of the quantum dot light emitting diodes were investigated. The electron blocking layer or the hole injection layer was added into the fundamental structure. The results of theoretical analyses showed that the improved device structure can regulate the potential barrier height and the injection efficiency of the holes and electrons. In this way, the concentration of the holes and electrons can reach to a certain balance in the quantum dots layer, which consequently decreases the influence of the Auger quenching process and the luminous efficiency will be improved.

Abstract: The ZnO nanorods-based ammonia (NH₃) gas sensors with different electrode spacing are fabricated and studied. Experimentally, the hexagonal ZnO nanorods were prepared by a hydrothermal method. The diameter and length of ZnO nanorods were about 179±2, 1806±5 nm, respectively. By shrinking the electrode spacing, the sensor response of studied device is improved and the sensor response is enhanced more than ten times in magnitude. The improved NH3 sensing ability caused by shrink electrode spacing is attributed to the presence of more grain boundaries and depletion layers. Therefore, the studied device with the shrink of electrode spacing provides a promise for high-performance ammonia sensing applications.

Abstract: This work is devoted to simulation of potential barrier spectrum for hydrogen atom and vacancy jumps in fcc- and bcc- metals taking into account the mutual effect of the point defects on the potential barrier spectrum and as a result the effect on complex defect diffusion in bcc- and fccmetals. The molecular static and the Monte Carlo methods are used. The developed model allows us to determine a diffusion coefficient of the impurity atom depending on temperature and other parameters. The simulation of point defect random walk in lattice on the basis MC-method and potential barrier spectrum has gave an impulse toward an understanding of hydrogen motion on the atomic scale in metals, which is required to determine such important parameters as the diffusion coefficient of H. As well it allows us to understand reasons of more complicated behaviour of H in realistic metal in comparison with perfect metal.

Abstract: The potential barrier at the metal/oxide junction in a specular spin valve structure with nano-oxide layers has been mapped by off-axis electron holography in a field emission gun transmission electron microscope. A potential jump of ~3V across the metal/oxide junction was detected. Presence of the potential barrier confirms formation of metal/insulator/metal structure, which contributes to confinement of conductance electrons with spin polarity characteristic in the key SV structure by the specular reflection of the spin-polarized electrons at the metal/oxide junction and leads to nearly double enhancement of magnetoresistance (MR) ratio from 8% to ~16%.