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A Study of Electrochemical and Charge-discharge Behavior of Tin Oxide andoLiang, Shih-Hao 25 July 2002 (has links)
Carbon-based materials are currently used for anodes in commercial lithium ion secondary batteries. The theoretical capacity for carbon is only 372mAh/g, and new materials are being developed for anodes to raise the electrical capacity and cycling times. One of the most promising materials is tin oxide that has 50% more electrical capacity and has been studied extensively in the industrial and academic institutions. While most studies have been concentrated on the electrochemical behavior in the charge-discharge process, microstructure evolution along with phase transformation have been emphasized in this work.
Tin oxide films are deposited on stainless steel substrate by sputtering and spray. A cell consists of a pure lithium foil as anode and tin oxide film as cathode along with 1M LiClO4 in DMC/EC mixture as electrolyte is fabricated and employed in the charge-discharge test and Cyclic Voltammetry. In the charge-discharge test, we use a constant current of 0.09mA to charge or discharge to the voltage that we need. In the Cyclic Voltammetry test, we change the scanning rate and scanning range. Microstructures developed and phase transformation in different stages of the charge-discharge or CV test process are examined by XRD, SEM and TEM.
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The Properties of Tantalate Modified Lithium Niobate Pyroelectric Thin Film Detectors Prepared by the Sol-Gel ProcessesWu, Jui-Chuan 03 July 2003 (has links)
The Ta-modified niobate lithium [LiNb1-xTaxO3, abbreviated to LNT] thin films were deposited on Pt/Ti/SiO2/Si substrates by spin coating with sol-gel technology and rapid thermal processing in this thesis. 1,3 propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of thin film. By changing the Ta content (x=0~1), the effects of various processing parameters on the thin films growth are studied. The effects of various Ta content on the response of pyroelectric IR detector devices are studied also.
Experimental results reveal that the Ta content will influence strongly on grain size, dielectricity, ferroelectricity and pyroelectricity of LNT thin films. With the increase of Ta content, the grain size of LNT thin film decreases slightly, and highly c-axis orientated LNT films have been obtained for x=0.2. With the increase of Ta content, The relative dielectric constant of LNT thin film increases from 33 up to 62. The dielectric loss (tand) increases from 0.00374 to 0.00686,Coercive Field (Ec) decreases from 81.09KV/cm to 32.07KV/cm, and Remanent polarization (Pr) decreases from 8.48 mC/cm2 to 2.2 mC/cm2, pyroelctric coefficient (g) increases from 2.76´10-8 C/cm2K up to 4.51´10-8 C/cm2K with an increase of Ta content. In addition, the results also show that the LNT thin film possesses the largest figures of merit Fv (2.66¡Ñ10-10 Ccm/J) and Fm (2.57¡Ñ10-8 Ccm/J) at the heating temperature of 700¢J and Ta content of 20mol%. The voltage responsivities (Rv) measured at 70 Hz has a largest value of 7020 V/W with the Ta content of 20mol%. The specific detectivity (D*) measured at 200 Hz has the maximum value of 7.76¡Ñ107 cmHz1/2/W with the Ta content of 20mol%. The results show that LNT(20) pyroelectric thin film detector exists both the maximums of voltage responsivity and specific detecivity. Therefore, optimizing the conditions of this study, LNT(20) thin film will be the most suitable for IR detector application.
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Evolution Study from Sol to SnO2 films Using Inorganic PrecursorsChen, Sing-Chung 31 July 2003 (has links)
Abstract
Aqueous solution containing tin chloride as precusor was traditionally added with NH3(aq) to promote hydrolysis and hence condensation. This results in a particulate sol which possesses little viscosity and the aggregation of precusor particles makes the subsequcently spin-coated thin film very rough in the surface and poorly-adhered with the substrate. One objective of this work is to improve the film quality by refluxing the sol to reduce precursor aggregation, enhance hydrolysis and promote HCl(g) evaporation.
Experimtntal results show that, after refluxing the sol with DI-water or methanol as solvent, one obtains better films when basic sol (NH3(aq) added) and SnCl2 precursor is used instead of acidic sol (HCl(aq)added) and SnCl4 precursor.
Moreover, to further reduce the effect of Cl¡Ð ion in aggregation and increase viscosity, ethylene glycol was used as solvent and two-stage heating-stirring of the sol in 80 oC and 130 oC ~150 oC was carried out to promote generation of H2O(g) and HCl(g). The evaporation of H2O(g) and HCl(g) enhances the polymerization of precursor and increase the viscosity of the sol. The aggregation caused by Cl¡Ð ions is thus reduced due to the steric effect present in the polymerical sol. XRD, SEM, FT-IR
, TGA and DSC were used to examine the evolution from sol to films. FT-IR results show that absorbtion peaks of the xerogel appear at 636 cm-1(O-Sn-O) and 500 cm-1 (Sn-O). XRD results of the calcined (4 hr) powders show that rutile (SnO2) crystallization starts at 200 oC for that derived from the SnCl2-containing sol while powder derived from the SnCl4-containing sol starts crystallization at 250 oC. However, grain growth is faster in powder derived from SnCl4-containing sol as their XRD peaks become sharper than that corresponding to SnCl2 precursor as calcination temperature is raised.
Based on the examination of the evolution process, it is concluded that SnCl2 polymerizes in ethylene glycol as a one dimensional chain while SnCl4 forming a 3-D network after polymerizing in ethylene glycol.
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A thin film transistor driven microchannel deviceLee, Hyun Ho 17 February 2005 (has links)
Novel electrophoresis devices for protein and DNA separation and identification
have been presented and studied. The new device utilizes a contact resistance change
detection method to identify protein and DNA in situ. The devices were prepared with a
microelectronic micromechanical system (MEMS) fabrication method. Three model
proteins and six DNA fragments were separated by polyacrylamide gel microchannel
electrophoresis and surface electrophoresis. The detection of the proteins or DNA
fragments was accomplished using the contact resistance increase of the detection
electrode due to adsorption of the separated biomolecules. Key factors for the success of
these devices were the optimization of fabrication process and the enhancement of
detection efficiency of the devices. Parameters, such as microchannel configuration, size
of electrode, and affinity of protein or polyacrylamide gel to the microchannel sidewall
and bottom surface were explored in detail. For DNA analysis, the affinity to the bottom
surface of the channel was critical. The surface modification method was used to
enhance the efficiency of the microchannel surface electrophoresis device. The
adsorption of channel separated protein and DNA on the detection electrode was
confirmed with the electron spectroscopy for chemical analysis (ESCA) method. The
electrical current (I) from the protein microchannel electrophoresis was usually noisy
and fluctuated at the early stage of the electrophoresis process. In order to remove the
current perturbation, an amorphous silicon (a-Si:H) thin film transistor (TFT) was
connected to the microchannel device. The self-aligned a-Si:H TFT was fabricated with
a two-photomask process. The result shows that the attachment of the TFT successfully
suppressed the current fluctuation of the microchannel electrophoresis process. In
summary, protein and DNA samples were effectively separated and detected with the
novel TFT-driven or surface microchannel electrophoresis device.
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Heat transfer enhancement in single-phase forced convection with blockages and in two-phase pool boiling with nano-structured surfacesAhn, Hee Seok 17 September 2007 (has links)
The first study researched turbulent forced convective heat (mass) transfer down-
stream of blockages with round and elongated holes in a rectangular channel. The
blockages and the channel had the same cross section, and a distance equal to twice
the channel height separated consecutive blockages. Naphthalene sublimation experiments were conducted with four hole aspect ratios (hole-width-to-height ratios) and
two hole-to-blockage area ratios (ratios of total hole cross-sectional area to blockage
area). The effects of the hole aspect ratio, for each hole-to-blockage area ratio, on the
local heat (mass) transfer distribution on the exposed primary channel wall between
consecutive blockages were examined. Results showed that the blockages with holes
enhanced the average heat (mass) transfer by up to 8.5 and 7.0 times that for fully
developed turbulent flow through a smooth channel at the same mass flow rate, respectively, in the smaller and larger hole-to-blockage area ratio (or smaller and larger
hole diameter) cases. The elongated holes caused a higher average heat (mass) transfer and a larger spanwise variation of the local heat (mass) transfer on the channel
wall than did the round holes.
The second study explored the heat transfer enhancement for pool boiling on
nano-structured surfaces. Experiments were conducted with three horizontal silicon surfaces, two of which were coated with vertically aligned multi-walled carbon nanotubes (MWCNT) with heights of 9 and 25 ùm, respectively, and diameters between
8 and 15 nm. The MWCNT arrays were synthesized on the two silicon wafers using
chemical vapor deposition. Experimental results were obtained over the nucleate boiling and film boiling regimes under saturated and sub-cooled (5ñC and 10ñC) boiling
conditions. PF-5060 was the test fluid. Results showed that the MWCNT array with
a height of 25 ùm enhanced the nucleate and film boiling heat fluxes on the silicon
surface by up to 380% and 60%, respectively, under saturated boiling conditions, and
by up to 300% and 80%, respectively, under 10ñC sub-cooled boiling conditions, over
corresponding heat fluxes on a smooth silicon surface. The MWCNT array with a
height of 9 ùm enhanced the nucleate boiling heat flux as much as the taller array,
but did not significantly enhance the wall heat flux in the film boiling regime.
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The Effect of Heat Treatments on the Opto-Electric Characteristic of Polymer Thin Film and its Application of PLEDYen, Hsu-Bin 17 July 2008 (has links)
The purpose of this research is to study the effect of the thermal treatment on the devices. We dissolved polymer light emitting materials in different solvents to discuss the influence on polymer thin film and device efficiency at different thermal conditions. We confirmed that the best thermal condition was changed as that of solvent changes.
In this study, we dissolved polymer blue light material¡ÐBP105 in Toluene and o-xylene. The glass transition temperature (Tg) of BP105 is 120.7¢J, and the boiling point of Toluene and o-xylene were 110 and 145¢J. That is namely the boiling point of Toluene and o-xylene are lower and higher, respectively, than the Tg of BP105. This makes us to compares the thermal treatment conditions on different influence from different boiling point of solvents. The interrelations between the thermal treatment temperature, the boiling point of solvents and the glass transition temperature of polymer is an interesting topic to study, because it does affect the surface morphology of polymer thin films and the characteristic of devices. The device structure is as follows: ITO/ PEDOT:PSS/ BP105/ LiF/ Ca/ Al.
Known from the experimental results that the spectra and the morphologies of polymer thin films will change in the different thermal treatment condition, and the choice of different solvent will also affect the best thermal treatment condition for device processing. We observed the surface roughness of polymer thin film is one of the important factors to affect the device efficiency in this study. We found that if the boiling point of used solvent was higher than the thermal treatment temperature, which was higher than the Tg of polymer, the surface roughness of polymer thin film is more smooth resulting in higher current injecting and higher stability of the device.
The best thermal treatment temperature is 130¢J by using o-xylene as solvent. The surface roughness of polymer thin film is 0.393 nm, and the maximum brightness of the device is 8593 cd/m2 at 12.5 V as a configuration of ITO(1500Å)/PEDOT:PSS(800Å)/BP105(650Å)/LiF(10Å)/ Ca(100Å)/ Al(2000Å). The luminous and the power efficiencies are 3.98 cd/A, and 1.43 lm/W, respectively, at the current density 100 mA/cm2.
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The Competitive Analysis on Taiwan Thin Film Solar Cell IndustryLIN, MENG-HUI 29 June 2009 (has links)
The energy crisis and environmental consciousness arising in recent years induce the rapid development of renewable energy technology, especially in solar energy field. Under the policy support of Germany and Japan, the solar energy market expands to the world speedily. Moreover, due to the high values of environmental protection topics in United Nations and European Union and Kyoto Protocol establishment, the renewable energy industry is imperative to prevail among the world. As a result of the industrial rapid growth, companies adopt all kinds of tactics to develop capability in order to occupy the renewable energy market.
Thanks to the remarkable achievement in LCD-TFT and semiconductor industries, Taiwan manufacturers applied the past experiences to invest in the solar cell industry, especially in thin film solar cell product. During 2005 to 2007, many companies found one after another.
This research mainly probes into the trend of Taiwan thin film solar cell industry. First, understand the competitors and global market conditions, then penetrate the industrial structure with Porter¡¦s five forces model, discuss the competitive advantage of Taiwan with Porter¡¦s diamond model, and look for the competitive ability of Taiwan thin film solar cell industry by SWOT analysis. Finally, the research proposes some developing suggestions for Taiwan thin film solar cell industry.
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The study of surface optical anisotropy of polyimide liquid crystal alignment layers by means of reflection anisotropy spectroscopyChen, Chao-yi 21 July 2009 (has links)
Reflection anisotropy spectroscopy (RAS) is a non-destructive optical technique which can be used to measure the surface properties of sample. We use the technique to detect the optical anisotropy of rubbed polyimide thin film.
Atomic force microscopy study of rubbed polyimide showed that rubbing produced microgrooves on the surface of the polyimide thin films, and the surface roughness of the polymer thin films increased slightly with the rubbing strength. Reflection anisotropy signals have been found to be generated on the surface of polyimide thin film on completion of mechanical rubbing, and will increase with an increase in the rubbing strength. We also tried to find out the correlation between RA strength of the polyimide alignment layer and pretilt angle of liquid crystal at the rubbed polyimide films.
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The Study and Fabrication of Optical Thin Film on Cr4+:YAG Double-clad Crystal Fiber Based DevicesLin, Si-rong 21 July 2009 (has links)
Recently, with the escalating demands for optical communications, the need for bandwidth in optical communication network has increased. The technology breakthrough in dry fiber fabrication opens the possibility for fiber bandwidth from 1.3 to 1.6 £gm. Cr4+:YAG double-clad crystal fiber (DCF) grown by the co-drawing laser-heated pedestal growth method has a strong spontaneous emission spectrum from 1.3 to 1.6 £gm. Such fiber is, therefore, eminently suitable for broadband optical amplifier, amplifier spontaneous emission (ASE) light source, tunable solid-state laser, and optical coherence tomography (OCT) applications.
In this thesis, multilayer dielectric thin films were directly deposited by E-gun coating onto the end faces of the heterostructure Cr4+:YAG DCF. In this way we have successfully improved the extracted ASE power by the high reflection (HR) coatings. The backward ASE in the fiber reflected and propagates with gain through the fiber in the forward direction. In dual-pump scheme, as much as 1.7 mW power (DCF length is 9.5 cm) of collimated output ASE was achieved. The dual-pump scheme and HR thin films provided 1.6 time improvements of the ASE output power. For broadband optical amplifier in dual-pump and double-pass scheme, a 3.7-dB gross gain and a 0.7-dB net loss (DCF length is 8.7 cm) at 1.4-£gm signal wavelength have been successfully developed with HR coatings onto one of the Cr4+:YAG DCF end faces. In addition, we have successfully developed the Cr4+:YAG DCF fiber laser by direct HR coatings onto fiber end faces. A record-low threshold of 96 mW (DCF length is 1.6 cm) with a slope efficiency of 6.9% was achieved at room temperature. It is more than four times lower than any previously reported Cr4+:YAG lasers.
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Development of FPW-based Mass Sensing Device with Reflection Grating Electrode DesignLai, Yu-zheng 31 August 2009 (has links)
The conventional medical immunoassays (ELISA/CLIA/FPIA) are not only costly (>10,000 USD), large in size (>10,000 cm3), but also require a vast number of sampling (25 £gL/well ¡Ñ 12 well) and long detection time (1~2.5 hr). To develop a biomedical microsensor for the application of portable detecting microsystem, this thesis proposes a flexural plate wave (FPW) microsensor with a novel reflection grating electrode (RGE) microstructure. Comparing to the conventional acoustic microsensors, the FPW based device has higher mass sensitivity, lower operation frequency but higher noise level. To overcome this disadvantages, this study added the RGE microstructure into the design of FPW sensor and investigated its influences on the reduction of insertion loss and noise level.
By using the surface and bulk micromachining technologies, this thesis designed and fabricated FPW-based mass-sensing device with a small volume of 0.189 cm3 and a novel RGE microstructure. The main processing steps adopted in this research include six photolithoghaphies and nine thin-film depositions. In this work, a high figure-of-merit C-axial orientation ZnO piezoelectric thin-film was deposited by a commercial magnetic radio-frequency (RF) sputter system. On the other hand, the gold/chrome interdigital transducer (IDT) and RGE aluminum electrode were deposited utilizing a commercial E-beam evaporator system. For the optimization of design specifications of the FPW devices, the space of input and output IDTs, pair number of IDT, length of delay line gap and with/without RGE design were varied and investigated.
Under the optimized IDT specification, the FPW microstructure presents lower central frequency (2¡ã4 MHz), insertion loss (-11 dB) and noise level (<-30 dB) than that of the FPW based microsensor without RGE microstructure. In addition, as the sampling volume of the testing DI water is equal to 1 £gL, a high mass sensitivity (-48.3 cm2/g) and short responding time (5 min) of the FPW microsensor with RGE design can be achieved in this work. The excellent characteristics mentioned above demonstrated the implemented FPW microsensor is very suitable for the applications of portable biomedical detecting microsystems.
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