Engineering topics

Selberherr, Siegfried

Publications and source records attributed to Selberherr, Siegfried.

4 records

DOE OSTI2014

Spin injection and diffusion in silicon based devices from a space charge layer

We have performed simulations on electron spin transport in an n-doped silicon bar with spin-dependent conductivity with or without the presence of an external electric field. We further consider three cases like charge neutrality, charge accumulation, and charge depletion at one boundary and found substantial differences in the spin transport behavior. The criteria determining the maximum spin current are investigated. The physical reason behind the transport behavior is explained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2014

Novel bias-field-free spin transfer oscillator

Two versions of magnetic field free spin torque oscillators with in- and out-of-plane spin polarizers are proposed. The field free spin torque oscillators comprise two spin valve stacks with a common free magnetic layer featuring an out-of-plane anisotropy. Their operation frequencies are controlled by the dimensions of the free layer and can also be tuned by the applied currents. Large and stable magnetization precessional motion of the whole shared free layer for both oscillators are obtained. The structure with in-plane polarizers allows more efficient microwave power extraction of the large in-plane magnetization precession of the free layer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2013

Strain-induced reduction of surface roughness dominated spin relaxation in MOSFETs

Semiconductor spintronics is a rapidly developing field with large impact on microelectronics. Using spin may help to reduce power consumption and increase computational speed. Silicon is perfectly suited for spin-based applications. It is characterized by a weak spin-orbit interaction which should result in a long spin lifetime. However, recent experiments indicate the lifetime is greatly reduced in gated structures. Thus, understanding the peculiarities of the spin-orbit effects on the subband structure and details of the spin propagation in surface layers and thin silicon films is urgently needed. We investigate the contribution of the spin-orbit interaction to the equivalent valley splitting and calculate the spin relaxation matrix elements by using a perturbative k ⋅p approach. We demonstrate that applying uniaxial stress along the [110] direction may considerably suppress electron spin relaxation in silicon surface layers and thin films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2013

ViennaX: a parallel plugin execution framework for scientific computing

We present the free open source plugin execution framework ViennaX for modularizing and parallelizing scientific simulations. In general, functionality is abstracted by the notion of a task, which is implemented as a plugin. The plugin system facilitates the utilization of both, already available functionality as well as new implementations. Each task can define arbitrary data dependencies which are used by ViennaX to build a task graph. The framework supports the execution of this dependence graph based on the message passing interface in either a serial or a parallel fashion. The applied modular approach allows for defining highly flexible simulations, as plugins can be easily exchanged. The framework's general design as well as implementation details are discussed. Applications based on the Mandelbrot set and the solution of a partial differential equation are investigated, and performance results are shown.

Weinbub, Josef↗