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Electrical Properties of TiO2 Thin Films on Si Substrate Prepared by MOCVDChen, Wei-Cheng 10 July 2003 (has links)
Recently, many dielectric materials have been considered as future promising candidates for a thin dielectric in DRAM storage capacitors.
Due to its properties of high dielectric constant (£`// = 170, £`¡æ = 89), high refractive index (~2.5) and high chemical stability. TiO2 is a promising candidate for fabricating thin dielectrics in dynamic random access memory (DRAM) storage capacitors and as gate dielectrics of metal-oxide-semiconductor field effect transistor (MOSFET) without the problem of conventional SiO2 thickness scaling down in ULSI processes because of its high dielectric constant.
TiO2 thin films grown on p-type (100) Si substrate are investigated by a cold wall horizontal MOCVD system using Ti(i-OC3H7)4, N2O and O2 as precursors in the growth temperature range from 400¢J to 700¢J.
The growth rate of using N2O as the oxidizer is quicker than the growth rate of using O2 as the oxidizer because N2O is the more efficient in producing free O atoms. XRD results indicate that the structures of TiO2 films are polycrystalline and the phase transformation temperature of TiO2 films from the anatase phase to the rutile phase is about 650¢J. Electrical properties are strongly influenced by the growth temperature. The electrical properties of as-grown TiO2 films can be improved by annealing treatment. The TiO2 films using O2 as the oxidizer at the growth temperature of 600¢J has the highest dielectric constant of 119.3 and the lowest leakage current density of 1.43¡Ñ10-6 A/cm2 at the applied electric field of 1 MV/cm after annealing for 20 minutes in O2. In order to obtain the better electrical properties of TiO2 films on Si substrate, we prepared TiO2 films by combination of MOCVD and LPD. The dielectric constant of post-annealed TiO2 films prepared by combination of MOCVD and LPD is 34.1. And the leakage current density of it is 3.7¡Ñ10-6 A/cm2 at the applied electric field of 1 MV/cm. It is lower than the films prepared in the same MOCVD-TiO2 growth condition (about 8.2¡Ñ10-6 A/cm2). It suggests that this growth method can reduce the leakage current density.
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Optimization of the configuration and working fluid for a micro heat pipe thermal control deviceCoughlin, Scott Joseph 12 April 2006 (has links)
Continued development of highly compact and powerful electronic components
has led to the need for a simple and effective method for controlling the thermal
characteristics of these devices. One proposed method for thermal control involves
the use of a micro heat pipe system containing a working fluid with physical properties
having been speciffcally selected such that the heat pipes, as a whole, vary in effective
thermal conductance, thereby providing a level of temperature regulation. To further
explore this possibility, a design scenario with appropriate constraints was established
and a model developed to solve for the effective thermal conductance of individual
heat pipes as a function of evaporator-end temperature. From the results of this
analysis, several working fluids were identified and selected from a list over thirteen
hundred that were initially analyzed. Next, a thermal circuit model was developed
that translated the individual heat pipe operating characteristics into the system as a
whole to determine the system level effects. It was found that none of the prospective
fluids could completely satisfy the established design requirements to regulate the
device temperature over the entire range of operating conditions. This failure to
fully satisfy design requirements was due, in large part, to the highly constrained
nature of problem definition. Several fluids, however, did provide for an improved
level of thermal control when compared to the unmodified design. Suggestions for improvements that may lead to enhanced levels of thermal control are offered as well
as areas that are in need of further research.
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Design of a novel conduction heating based stress-thermal cycling apparatus for composite materials and its utilization to characterize composite microcrack damage thresholdsJu, Jaehyung 30 October 2006 (has links)
The objective of this research was to determine the effect of thermal cycling
combined with mechanical loading on the development of microcracks in M40J/PMR-II-
50, the second generation aerospace application material. The objective was pursued by
finding the critical controlling parameters for microcrack formation from mechanical
stress-thermal cycling test.
Three different in-plane strains (0%, 0.175~0.350%, and 0.325~0.650%) were applied
to the composites by clamping composite specimens (M40J/PMR-II-50, [0,90]s, a unitape
cross-ply) on the radial sides of half cylinders having two different radii (78.74mm
and 37.96mm). Three different thermal loading experiments, 1) 23oC to âÂÂ196oC to 250oC,
2) 23oC to 250oC, and 3) 23oC to -196oC, were performed as a function of mechanical inplane
strain levels, heating rates, and number of thermal cycles. The apparatus generated
cracks related to the in-plane stresses (or strains) on plies. The design and analysis
concept of the synergistic stress-thermal cycling experiment was simplified to obtain main and interaction factors by applying 2k factorial design from the various factors
affecting microcrack density of M40J/PMR-II-50.
Observations indicate that the higher temperature portion of the cycle under load
causes fiber/matrix interface failure. Subsequent exposure to higher stresses in the
cryogenic temperature region results in composite matrix microcracking due to the
additional stresses associated with the fiber-matrix thermal expansion mismatch.
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Thermal properties of an upper tidal flat sediment on the Texas Gulf CoastCramer, Nicholas C. 25 April 2007 (has links)
Increased land use change near fragile ecosystems can affect the ecosystem energy
balance leading to increased global warming. One component of surface energy balance
is soil storage heat flux. In past work, a complex thermal behavior was noticed in the
shrink-swell sediment of the upper Nueces Delta (upper Rincon) during summer months
as it dried. Soil storage heat flux was found to first increase, then decrease, as the soil
dried. It was suggested that the complex behavior was due to the relationship between
thermal diffusivity and soil moisture, where thermal diffusivity increases to a local
maximum before decreasing with respect to decreasing soil moisture. This study
explores the observed phenomenon in a controlled laboratory environment by relating
the sediment shrinkage curve to changing heat transfer properties.
Due to the complicated nature of the drying-shrinking sediment, it was necessary to
measure the sediment shrinkage curve and heat transfer properties in separate
experiments. The shrinkage curve was found by correlating measured sample volume
with gravimetric moisture content. Heat transfer properties were found using a single
needle heat pulse probe. A normalized gravimetric moisture content was used as a
common variable to relate the shrinkage curve and heat transfer data. Data suggests that the shrink-swell Rincon sediment portrays different behavior in
drying than that which occurs for a non-shrink-swell soil. For the shrink-swell Rincon
sediment, thermal conductivity is seen to increase with decreasing moisture, the
suggested mechanism being increased surface area contact between particles as the
shrinking sediment dries.
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The transport coefficients in (R1.5Ce0.5)RuSr2Cu2O10-5 (R=Gd,Eu) rutheno-cupratesAnatska, Maryna Petrovna 25 April 2007 (has links)
The thermal conductivity, thermopower, and electrical resistivity of
(R1.5Ce0.5)RuSr2Cu2O10-delta (R=Gd, Eu) polycrystalline samples with different oxygen
doping level are investigated in temperature range 1.8-300 K. Much attention is focused
on the dependence of the effect of the annealing in high oxygen pressures as well as the
effect of aging on transport coefficients in normal and superconducting states. It was
found that the process of deoxydation goes faster for Ru-1222(Eu) samples than for Ru-
1222(Gd) samples, which results in more pronounced granular effects in Ru-1222(Eu)
samples. The relative contribution to the thermal conductivity due to electrons and
phonons was estimated by using the Wiedemann-Franz relation and the resistivity data.
The calculation showed that the maximum electron contribution for Ru-1222(Eu) is
about 0.75% and that for Ru-1222(Gd) samples is around 4 %.
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Analysis of a technique of measuring the thermal diffusivity of poor conductors /Ohlwiler, Robert William. January 1964 (has links)
Thesis (M.S.)--Ohio State University, 1964. / Available online via OhioLINK's ETD Center
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A consideration of cycle selection for meso-scale distributed solar-thermal powerPrice, Suzanne. January 2009 (has links)
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Mayor, James Rhett; Committee Member: Garimella, Srinivas; Committee Member: Jeter, Sheldon. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Thermal buckling of laminated composite plates /Simelane, Philemon Sphiwe. January 1900 (has links)
Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 1998. / Word processed copy. Summary in English. Includes bibliographical references (leaves 95-96). Also available online.
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Quantifying the impact of thermal lensing on visual function in ocular mediaWeber, Erica L. 12 November 2013 (has links)
Several studies have been conducted in the past which determined that some near-infrared (NIR) sources are capable of inducing a thermal lens within ocular media of rhesus and, potentially, human subjects. Typically, the role of thermal lensing in the eye was explored in terms of its influence on damage thresholds for these NIR lasers entering the eye. However, the effect of a thermal lens on visible wavefronts entering the eye has yet to be explored. In recent years military and law enforcement agencies in the United States and elsewhere have devoted considerable resources to the area of "non-lethal weapons." Devices such as tasers, spike strips and ocular interruption (OI) devices provide the user with an escalation of force while minimizing casualties and collateral damage. One particular form of OI device, the laser dazzler, employs a visible laser capable of saturating retinal receptors causing a temporary flash blindness effect. While these visible devices have proven safe and effective in the field, an inherent risk exists when any light source is used to saturate retinal tissue. By adding the use of a thermal lens, these OI devices would create significant distortions in the visible wavefront to alter vision and/or increase the diameter of a focused visible dazzler at the retina to both improve safety and effectiveness of the visible device. This dissertation describes experiments involving artificial eye, human subject, and computational modeling which were conducted to quantify the impact of thermal lensing on visual acuity. / text
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Cast keepers for dental magnets: effects of laboratory procedures陳鴻釗, Chan, Hung-chiu, Kingsley. January 2005 (has links)
published_or_final_version / Dentistry / Master / Master of Dental Surgery
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