Home  About us  Contact
 

Temperature Operation (temperature + operation)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

A Novel Device for Single Particle Light Scattering Size Analysis and Concentration Measurement at High Pressures and Temperatures

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 2 2008
Heinz Umhauer
Abstract Based on the findings of previous work, a novel instrument was developed for the size analysis and concentration measurement of particles dispersed in gases at high temperatures (600,°C) and pressures (16 bar). The main motivation for the construction of this device was a measurement requirement at the conditions of a pressurized pulverized coal combustion (PPCC) test installation in Dorsten, Germany. The development of a high efficiency (>,50,%), coal based, combined cycle process, and specifically, the development of efficient gas cleaning technology for gas combustion under demanding conditions (1400,°C and 16 bar) was the main target. A suitable measurement technique was required for the determination of particle size and concentration downstream of the gas cleaning equipment, which is able to operate close to the given conditions. The performance of the novel device was tested in several measurement series with various monodisperse aerosols at ambient conditions as well as in high pressure, high temperature situations with very satisfactory results, i.e., the lower detection limit (50,% counting efficiency at ca. 0.3 ,m) and resolution of the novel device are comparable to state of the art instruments (of the same principle) intended for room temperature operation. [source]

Reliability and degradation mechanism of AlGaAs/InGaAs and InAlAs/InGaAs HEMTs

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
M. Dammann
Abstract The long-term stability of AlGaAs/GaAs and InAlAs/InGaAs high electron mobility transistors (HEMTs), tested under high drain voltage and/or high temperature operation is reported. HEMTs with high In content in the active channel, alternatively fabricated on InP substrates and on GaAs substrates covered by a metamorphic buffer (MHEMT), are compared. Despite the high dislocation density in the buffer layer MHEMTs and InP based HEMTs exhibit comparable reliability. AlGaAs/GaAs HEMTs are more reliable than their InAlAs/InGaAs counterparts, especially when operated at high drain voltage. Failure mechanisms are thermally activated gate sinking, Ohmic contact degradation and hot electron induced degradation. [source]

Crystallographically oriented high resolution lithography of graphene nanoribbons by STM lithography

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2010
G. Dobrik
Abstract Due to its exciting physical properties and sheet-like geometry graphene is in the focus of attention both from the point of view of basic science and of potential applications. In order to fully exploit the advantage of the sheet-like geometry very high resolution, crystallographicaly controlled lithography has to be used. Graphene is a zero gap semiconductor, so that a field effect transistor (FET) will not have an "off" state unless a forbidden gap is created. Such a gap can be produced confining the electronic wave functions by etching narrow graphene nanoribbons (GNRs) typically of a few nanometers in width and with well defined crystallographic orientation. We developed the first lithographic method able to achieve GNRs that have both nanometer widths and well defined crystallographic orientation. The lithographic process is carried out by the local oxidation of the sample surface under the tip of a scanning tunneling microscopy (STM). Crystallographic orientation is defined by acquiring atomic resolution images of the surface to be patterned. The cutting of trenches with controlled depth and of a few nanometer in width, folding and manipulation of single graphene layers is demonstrated. The narrowest GNR cut by our method is of 2.5,nm width, scanning tunneling spectroscopy (STS) showed that it has a gap of 0.5,eV, comparable to that of germanium, which allows room temperature operation of graphene nanodevices. [source]

Branching-induced spin polarization amplification in nonmagnetic semiconductors

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2006
S.-W. Jung
Abstract We study the spin injection in ferromagnet-tunnel barrier-semiconductor heterojunction structure embedded in the current-branching scheme. The current branching enables one to separately control the charge current from the spin current. As a result, it is possible to electrically control the spin current polarization within the semiconductor. Moreover, it can be enhanced further and may reach 100% by properly tuning the branched currents. Since the proposed scheme does not require low temperature operation, it may be a useful tool to generate the high spin current polarization at room temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]