Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physics
Limitations Of Zt As A Figure Of Merit For Nanostructured Thermoelectric Materials, Xufeng Wang, Mark Lundstrom
Limitations Of Zt As A Figure Of Merit For Nanostructured Thermoelectric Materials, Xufeng Wang, Mark Lundstrom
Department of Electrical and Computer Engineering Faculty Publications
Thermoelectric properties of nanocomposites are numerically studied as a function of average grain size or nanoparticle density by simulating the measurements as they would be done experimentally. In accordance with previous theoretical and experimental results, we find that the Seebeck coefficient, power factor and figure of merit, zT, can be increased by nanostructuring when energy barriers exist around the grain boundaries or embedded nanoparticles. When we simulate the performance of a thermoelectric cooler with the same material, however, we find that the maximum temperature difference is much less than expected from the given zT. This occurs because the …
Ballistic-Ohmic Quantum Hall Plateau Transition In A Graphene P-N Junction, Tony Low
Ballistic-Ohmic Quantum Hall Plateau Transition In A Graphene P-N Junction, Tony Low
Birck and NCN Publications
Recent quantum Hall experiments conducted on disordered graphene p-n junction provide evidence that the junction resistance could be described by a simple Ohmic sum of the n and p mediums’ resistances. However in the ballistic limit, theory predicts the existence of chirality-dependent quantum Hall plateaus in a p-n junction. We show that two distinctively separate processes are required for this ballistic-Ohmic plateau transition, namely, (i) hole/electron Landau states mixing and (ii) valley isospin dilution of the incident Landau edge state. These conclusions are obtained by a simple scattering theory argument, and confirmed numerically by performing ensembles of quantum magnetotransport calculations …
Electronic Transport Properties Of A Tilted Graphene P-N Junction, Tony Low, Joerg Appenzeller
Electronic Transport Properties Of A Tilted Graphene P-N Junction, Tony Low, Joerg Appenzeller
Birck and NCN Publications
Spatial manipulation of current flow in graphene could be achieved through the use of a tilted p-n junction. We show through numerical simulation that a pseudo-Hall effect (i.e., nonequilibrium charge and current density accumulating along one of the sides of a graphene ribbon) can be observed under these conditions. The tilt angle and the p-n transition length are two key parameters in tuning the strength of this effect. This phenomenon can be explained using classical trajectory via ray analysis, and is therefore relatively robust against disorder. Lastly, we propose and simulate a three terminal device that allows direct experimental access …
Modeling Of Spin Metal-Oxide-Semiconductor Field-Effect Transistor: A Nonequilibrium Green’S Function Approach With Spin Relaxation, Tony Low, Mark Lundstrom, Dmitri Nikonov
Modeling Of Spin Metal-Oxide-Semiconductor Field-Effect Transistor: A Nonequilibrium Green’S Function Approach With Spin Relaxation, Tony Low, Mark Lundstrom, Dmitri Nikonov
Birck and NCN Publications
A spin metal-oxide-semiconductor field-effect transistor (spin MOSFET), which combines a Schottky-barrier MOSFET with ferromagnetic source and drain contacts, is a promising device for spintronic logic. Previous simulation studies predict that this device should display a very high magnetoresistance (MR) ratio (between the cases of parallel and antiparallel magnetizations) for the case of half-metal ferromagnets (HMF). We use the nonequilibrium Green’s function formalism to describe tunneling and carrier transport in this device and to incorporate spin relaxation at the HMF-semiconductor interfaces. Spin relaxation at interfaces results in nonideal spin injection. Minority spin currents arise and dominate the leakage current for antiparallel …