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Interface Quality (interface + quality)

Distribution by Scientific Domains
Physics and Astronomy60%

Selected Abstracts

Microstructure and Microfabrication Considerations for Self-Supported On-Chip Ultra-Thin Micro-Solid Oxide Fuel Cell Membranes

FUEL CELLS, Issue 5 2009
B.-K. Lai
Abstract La0.6Sr0.4Co0.8Fe0.2O3,,,, (LSCF) has been sputtered on bare Si and Si3N4 and yttria-stabilised zirconia (YSZ) thin films to investigate annealing temperature- and thickness-dependent microstructure and functional properties, as well as their implications for designing failure-resistant micro-solid oxide fuel cell (,SOFC) membranes. The LSCF thin films crystallise in the 400,450,°C range; however, after annealing in the 600,700,°C range, cracks are observed. The formation of cracks is also thickness-dependent. High electrical conductivity, ,520,Scm,1 at 600,°C, and low activation energy, ,0.13,eV, in the 400,600,°C range, are still maintained for LSCF films as thin as 27,nm. Based on these studies, a strong correlation between microstructure and electrical conductivity has been observed and an annealing temperature-thickness design space that is complementary to temperature-stress design space has been proposed for designing reliable membranes using sputtered LSCF thin films. Microfabrication approaches that maintain the highest possible surface and interface quality of heterostructured membranes have been carefully examined. By taking advantage of the microstructure, microfabrication and geometrical structural considerations, we were able to successfully fabricate large-area, self-supported membranes. These results are also relevant to conventional or grid-supported SOFC membranes using ultrathin nanocrystalline cathodes and ,SOFCs using cathode thin films other than LSCF. [source]

Thickness dependence of magnetic coupling strength and thermal stability in a spin-dependent tunnel junction

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004
C. H. Nam
Abstract The change of magnetic coupling strength between two ferromagnetic layers, separated by an insulating barrier, was investigated as a function of the barrier thickness (TB) and thermal annealing temperatures. The magnetic junctions consist of Ta/CoFe/AlOx/NiFe/Ta layers with three different nominal thickness of TB = 1.3, 1.6, and 2.0 nm. Isothermal magnetization at room temperature revealed that, while the junction with a lower TB showed a higher magnetic coupling strength, thermal annealing at T = 225 °C increased (and diminished) the coupling strength of the junctions with TB = 1.3 and 1.6 nm (and 2.0 nm), respectively. This observation was utilized to understand consistently the magneto-resistance behavior and specific junction resistance of the junctions as a function of thermal annealing temperature. This study demonstrated that the physical properties of a magnetic tunnel junction, such as magneto-resistance ratio, specific junction resistance and their thermal stability, were substantially influenced by the insulating barrier structure as well as the interface quality between the layers. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Study of metal-oxide-semiconductor capacitors with r.f. magnetron sputtering TiOxNy films dielectric layer

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Katia Franklin Albertin
Abstract A set of MOS capacitors with TiOxNy films as gate dielectric layer was fabricated and characterized. The TiOxNy films were deposited by reactive r.f. magnetron sputtering varying the nitrogen and oxygen partial pressure in a Ar/N2/O2 gaseous mixture. The TiOxNy films were characterized by, Rutherford Backscattering (RBS), X-ray absorption near edge spectroscopy (XANES) in oxygen K-edge (O-K), optical absorption and High Resolution Transmission Electron Microscopy (HRTEM). Capacitance-voltage (1MHz) and current-voltage measurements were performed to obtain the effective dielectric constant, the effective oxide thickness (EOT), the leakage current density, and the interface quality. MOS capacitors results show that the TiOxNyfilms dielectric constant varies from 28 to 80, present a good interface quality with silicon, and the leakage current density values are in the order of 0.25 mA/cm2 for VG = ,2V, which is acceptable for high performance logic circuits and low power circuits fabrication. The leakage current density is reduced in 2 orders of magnitude for increasing nitrogen concentration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

High-efficiency copper indium gallium diselenide (CIGS) solar cells with indium sulfide buffer layers deposited by atomic layer chemical vapor deposition (ALCVD)

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2003
N. Naghavi
Abstract This paper presents optimization studies on the formation of indium sulfide buffer layers for high-efficiency copper indium gallium diselenide (CIGS) thin-film solar cells with atomic layer chemical vapour deposition (ALCVD) from separate pulses of indium acetylacetonate and hydrogen sulfide. A parametric study of the effect of deposition temperature between 160° and 260°C and thickness (15,30,nm) shows an optimal value at about 220°C for a layer thickness of 30,nm, leading to an efficiency of 16·4%. Analysis of the device shows that indium sulfide layers are characterised by an improvement of the blue response of the cells compared with a standard CdS-processed cell, due to a high apparent band gap (2·7,2·8,eV), higher open-circuit voltages (up to 665,mV) and fill factor (78%). This denotes high interface quality. Atomic diffusion processes of sodium and copper in the buffer layer are demonstrated. Copyright © 2003 John Wiley & Sons, Ltd. [source]