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Compatibility of electrolyte and electrode materials for intermediate temperature solid oxide fuel cellsWilliams, Caroline January 2000 (has links)
No description available.
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The study of barrier mechanisms of tantalum nitride diffusion barrier layer between GaAs and CuYueh, Zhi-Wei 20 June 2000 (has links)
Abstract
The behaviors of the TaNx barrier layer that placed
between the Cu metal and GaAs have been studied
by using X-ray diffraction, X-ray photoelectron
spectroscopy and scanning electron microscopy.
The TaNx and Cu films were deposited on GaAs
sequentially with RF magnetron sputter.
With a 250 nm thick TaNx barrier layer, the Cu
metal can be impeded from reacting with GaAs
substrate at 575¢Jannealed for one hour.
Within an As or Ga overpressure environment condition,
the failure temperature still occurred below 600¢J.
The failure of TaNx diffusion barrier layer for
preventing the reaction of the Cu and GaAs was originated
for the dissociation of the GaAs itself at 580¢J.
The outgoing As atoms increased the deterioration speed
of the TaNx film and reduced its blocking ability.
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Development of a Dense Diffusion Barrier Layer for Thin Film Solar CellsPillay, Sankara January 2009 (has links)
<p>Tantalum diffusion barrier coatings were investigated as a way to improve the conversion efficiency of CIGS (copper indium gallium diselenide) solar cells. Tantalum coatings were deposited upon silicon and stainless steel foil substrates using direct current magnetron sputtering (DcMS) and high power impulse magnetron sputtering (HiPIMS). The coatings were characterized using scanning electron microscopy (SEM). Cross-sectional scanning electron micrographs revealed that the HiPIMS coatings appeared denser than the DcMS coatings.</p>
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Development of a Dense Diffusion Barrier Layer for Thin Film Solar CellsPillay, Sankara January 2009 (has links)
Tantalum diffusion barrier coatings were investigated as a way to improve the conversion efficiency of CIGS (copper indium gallium diselenide) solar cells. Tantalum coatings were deposited upon silicon and stainless steel foil substrates using direct current magnetron sputtering (DcMS) and high power impulse magnetron sputtering (HiPIMS). The coatings were characterized using scanning electron microscopy (SEM). Cross-sectional scanning electron micrographs revealed that the HiPIMS coatings appeared denser than the DcMS coatings.
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Magnetodielectric study on double perovskite Pr2CoMnO6Chang, Jie-Hao 02 July 2012 (has links)
We report an intriguing giant dielectric and magnetodielectric (MD)
response on double perovskite Pr2CoMnO6(PCMO) system. The Arrhenius
plot indicates that the origin of giant dielectric is internal barrier layer
capacitance. Meanwhile, at the highest applied magnetic field 9T, the giant
dielectric constant around Tm ~ 150 K is enhanced almost ~ 20% (at 10 kHz
frequency) compared with that at zero field. The observed positive MD
effect is considered to be associated with the direct consequence of
negative magnetoresistance changes (~ -20% at 150 K) which was
calculated by temperature dependent impedance spectras. Concomitantly, a
pronounced ferromagnetic ordering is observed near Tc ~ 150 K coinciding
with Tm of £`¡¬(T). These experimental results suggest that the
magnetoresistive and MD effect response is very strongly by magnetic
property of PCMO.
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Theoretical Study of Semiconductor Quantum Dot Lasers with Asymmetric Barrier LayersMonk, John Lawrence III 21 May 2020 (has links)
Small-signal dynamic response of semiconductor quantum dot (QD) lasers with asymmetric barrier layers was studied. Semiconductor lasers are used in many communication systems. Fiber optic communication systems use semiconductor lasers in order to transmit information. DVD and Blu-ray disk players feature semiconductor lasers as their readout source. Barcode readers and laser pointers also use semiconductor lasers. A medical application of semiconductor lasers is for minor soft tissue procedures. Semiconductor lasers are also used to pump solid-state and fiber lasers. Semiconductor lasers are able to transmit telephone, internet, and television signals through fiber optic cables over long distances. The amount of information able to be transferred is directly related to the bandwidth of the laser. By introducing asymmetric barrier layers, the modulation bandwidth of the laser will improve, allowing for more information to be transferred. Also, by introducing asymmetric barrier layers, the output power will be unrestricted, meaning as more current is applied to the system, the laser will get more powerful. An optimum pumping current was found which maximized modulation bandwidth at -3dB, and is lower in QD lasers with asymmetric barrier layers (ABL) as opposed to conventional QD lasers. Modulation bandwidth was found to increase with cross section of carrier capture before reaching an asymptote. Both surface density of QDs and cavity length had optimum values which maximized modulation bandwidth. Relative QD size fluctuation was considered in order to see how variation in QD sizes effects the modulation bandwidth of the semiconductor QD laser with ABLs. These calculations give a good starting point for fabricating semiconductor QD lasers with ABLs featuring the largest modulation bandwidth possible for fiber optic communication systems.
In semiconductor QD lasers, the electrons and holes may be captured into excited states within the QDs, rather than the ground state. The particles may also jump from the ground state up to an excited state, or drop from the excited state to the ground state. Recombination of electron-hole pairs can occur from the ground state to the ground state or from an excited state to an excited state. In the situation if the capture of charge carriers into the ground state in QDs takes place via the excited-state, then this two-step capture process makes the output power from ground-state lasing to saturate in conventional QD lasers. By using ABLs in the QD laser, it is predicted that the output power of ground-state lasing will continue to rise with applied current, as the ABLs will stop the electrons and holes from recombining in the optical confinement layer. Thus, ABL QD lasers will be able to be used in applications that require large energy outputs. / Master of Science / Semiconductor lasers (also known as diode lasers) have been used in numerous applications ranging from communication to medical applications. Among all applications of diode lasers, of particular importance is their use for high speed transmission of information and data in fiber optic communication systems. This is accomplished by direct conversion of the diode laser input (electrical current) to its output (optical power). Direct modulation of the laser optical output through varying electrical current helps cut costs by not requiring other expensive equipment in order to perform modulation.
The performance of conventional semiconductor lasers suffers from parasitic recombination outside of the active region – an unwanted process that consumes a considerable fraction of the laser input (injection current) while not contributing to the useful output and thus damaging its performance.
Asymmetric barrier layers were proposed as a way to suppress parasitic recombination in semiconductor lasers. In this study, the optimal conditions for semiconductor quantum dot lasers with asymmetric barrier layers were calculated in order to maximize their modulation bandwidth – the parameter that determines the highest speed of efficient information transmission. This includes finding the optimal values of the dc component of the pump current, quantum dot surface density and size fluctuations, and cavity length. As compared to conventional quantum dot lasers, the optimal dc current maximizing the modulation bandwidth is shown to be considerably lower in quantum dot lasers with asymmetric barrier layers thus proving their outperforming efficiency.
In the presence of extra states in quantum dots in conventional lasers, the optical output of needed ground-state lasing may be heavily impacted – it may remain almost unchanged with increasing the laser input current. As opposed to conventional lasers, the output power of ground-state lasing in devices with asymmetric barrier layers will continue growing as more input current is applied to the system.
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Barrier Layer Concepts in Doped BaTiO3 CeramicsTennakone, Harshani 30 September 2013 (has links)
No description available.
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HIGH STRAIN FUNCTIONALLY GRADED BARIUM TITANATE AND ITS MATHEMATICAL CHARACTERIZATIONSURANA, RAJESH R. January 2004 (has links)
No description available.
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Room-temperature continuous-wave operation of GaInNAs/GaAs quantum dot laser with GaAsN barrier grown by solid source molecular beam epitaxySun, Z. Z., Yoon, Soon Fatt, Yew, K. C., Bo, B. X., Yan, Du An, Tung, Chih-Hang 01 1900 (has links)
We present the results of GaInNAs/GaAs quantum dot structures with GaAsN barrier layers grown by solid source molecular beam epitaxy. Extension of the emission wavelength of GaInNAs quantum dots by ~170nm was observed in samples with GaAsN barriers in place of GaAs. However, optimization of the GaAsN barrier layer thickness is necessary to avoid degradation in luminescence intensity and structural property of the GaInNAs dots. Lasers with GaInNAs quantum dots as active layer were fabricated and room-temperature continuous-wave lasing was observed for the first time. Lasing occurs via the ground state at ~1.2μm, with threshold current density of 2.1kA/cm[superscript 2] and maximum output power of 16mW. These results are significantly better than previously reported values for this quantum-dot system. / Singapore-MIT Alliance (SMA)
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Polohové řízení solárního panelu s optimalizací energetické účinnosti / Positioner for Solar Panel with Power Efficiency OptimizingKreysa, Karel January 2011 (has links)
This thesis is focused on design and prototyping of solar panel position control system for an obtaining of the maxima renewable energy from sun. In this thesis, various ways of solar panel positioning are considered and analyzed. Consequently, a construction arrangement of the positioner is presented. It is mechanically adapted to obtain the maximum efficiency in typical environment corresponding with the Central European geographical latitude. Different methods of sun monitoring are considered and analyzed. On the basis of this analysis, a proper prototype of sun monitor for exact positioning with disturbance filtering has been constructed. Following part of work is devoted to stable, fully automated, control subsystem for reliable functionality of solar system. A suitable microprocessor with a robust firmware has been implemented to this control unit. Finally, system parameters measurement and closing analysis of gained renewable energy and backflow computation is presented in the end of this diploma thesis.
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