Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13843号 / 工博第2947号 / 新制||工||1435(附属図書館) / 26059 / UT51-2008-C759 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 金谷 利治, 教授 吉﨑 武尚, 教授 渡辺 宏 / 学位規則第4条第1項該当

ZnO is an n-type semiconducting material with high optical transparency in the visible range (400 - 750 nm) of the electromagnetic spectrum. When doped with group 13 or 14 metal oxides, ZnO exhibits almost metallic electrical conductivity. ZnO thin films have been recognised as promising alternative material for the currently widely-used but expensive indium oxide in the form of indium tin oxide (ITO), in terms of their low cost and the high abundance of zinc. At the moment, even the best solution-processed ZnO films still can not compete for ITO replacement especially in solar energy utilization and OLED lighting applications, and the performance of ZnO films needs to be further improved. The objective of this work was to enhance the electrical and optical properties of spray pyrolysed ZnO thin films by simultaneous cation and anion doping. This was achieved by growing several series of undoped, single-doped, and co-doped ZnO thin films over a wide range of conditions, in order to understand the growth behaviour of undoped and doped ZnO, and to establish the optimum growth procedure. Spray pyrolysis process has advantages over vacuum-based techniques in terms of its low-cost, high deposition rate, simple procedure and can be applied for the production of large area thin films. Various techniques were employed to characterize the properties of the prepared thin films, and thus determine the optimum growth conditions (i.e. X-ray difiraction (XRD), Xray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-Vis-NIR spectroscopy and Hall effect measurement). The growth of doped ZnO on glass substrates using Si and F as dopants, yielded highly conducting and transparent thin films. The co-doped thin films exhibited distinct widening of band gap upon increasing deposition temperature and doping concentration as a result of increasing electron concentration up to 4.8 x 10²⁰ cm^-3 upon doping with Si and F at the same time. The resistivity of the films deposited from Zn(acac)₂ · xH₂O solutions and at the optimum temperature of 450 °C, was found to decrease from 4.6 x 10^-2 Ωcm for the best undoped ZnO film to 3.7 x 10^-3 Ωcm, upon doping with 3% Si. The films co-doped with Si and F in the ratios of [Si] / [Zn]= 3 - 4 mol% and [F] / [Zn]=30 - 40 mol% were the most conducting (p ∼ 2.0 x 10^-3 Ωcm). The associated optical transmittance of co-doped ZnO was above 85% in the whole visible range. Results compare favourably with In-doped ZnO deposited under similar conditions. Si+F co-doped ZnO films offer a suitable replacement for ITO in many applications such as LCD and touch screen displays.

In this tribological study, a temperature dependent inquiry of the changes in chemistry and crystal structure of two selected double metal oxides is undertaken. It is known that chameleon coatings of Mo2N/Ag/MoS2 produce a friction coefficient of 0.1 from wear testing at 600 °C for 300,000 cycles. The low friction is attributed to the formation of silver molybdates layers, a lubricious double-metal oxide, in the coating. Double-metal oxides consisting of a group 6 transitional metal and silver (silver molybdate (Ag2Mo2O7) and silver tungstate (Ag2WO4)) were used for this investigation. Thin films and powders were investigated using high temperature x-ray diffraction, high-temperature Raman spectroscopy and differential scanning calorimetry in tandem with sliding tests from 25 to 600 °C. Our results were compared to external ab-initio molecular dynamic simulations performed elsewhere to qualify experimental results. The layered atomic structure of silver molybdate facilitates sliding, resulting in a low coefficient of friction (<0.2) from 300-500 °C. Unlike Ag2Mo2O7, however, Ag2WO4 does not possess a layered atomic structure and produced coefficients of friction (>0.4) in all temperature ranges between room temperature and 500 °C. Applying the knowledge gained from prior studies of the intrinsic properties of double metal oxides of group 6, chameleon coatings consisting of group 5 transitional metal nitrides (vanadium nitride, niobium nitride, and tantalum nitride) with silver inclusions were created using unbalanced magnetron sputtering to investigate their potential application as adaptive, friction reducing coatings. The coatings were tribotested against a Si3N4 counterface in the 22 to 1000 °C temperature range. In-situ Raman Spectroscopy measurements were taken during heating and wear testing at 700 °C to identify the evolution of phases in the coatings' surfaces and in the wear track. The chemical and structural properties of the coatings were also characterized before and after wear testing using x-ray diffraction. At higher temperatures, oxygen, silver and the transition metals react on the surface to form potentially lubricious double oxide phases (silver vanadate, silver niobate and silver tantalate). All coatings performed similarly up to 750 °C. The VN/Ag coating, however, had a lower coefficient of friction at 750 °C comparatively to TaN/Ag and NbN/Ag, likely due to its reported lower melting temperature (450 °C) and its layered crystal structure.

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-09-11Bitstream added on 2014-06-13T20:06:34Z : No. of bitstreams: 1 alencar_mas_dr_araiq.pdf: 4202119 bytes, checksum: 35fa6bb33ce6843d922c597e61ac48c8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os vidros calcogenetos a base de telúrio vem despertando grande interesse acadêmico e tecnológico devido às suas versáteis propriedades ópticas, elétricas e físico-químicas, permitindo a sua aplicação em várias áreas da fotônica. Este trabalho descreve o estudo cinético de cristalização e dos fenômenos fotoinduzidos no sistema vítreo Ga-Ge-Te. Duas composições, Ga20Ge10Te70 (GGT7) e Ga10Ge10Te80 (GGT10), tiveram sua cinética de cristalização estudadas, nos vidros com tamanho de partículas de 53<x>45 μm e em monolito, analisando-se a fração cristalizada. Foi possível calcular a energia de ativação pelos métodos de Kissinger, Ozawa, e Augis e Benett e o expoente de Avrami, que fornece informações dos processos de nucleação e crescimento de cristais para ambas as composições. Os dados obtidos mostram que estas composições apresentaram altos valores de energia de ativação, característica interessante em aplicações onde a estabilidade da fase amorfa seja requerida. Na segunda parte do trabalho foram produzidos filmes finos por “Electron Beam Physical Vapor Deposition” utilizando as composições vítreas GGT7 e GGT10. Os efeitos fotoinduzidos foram avaliados nos filmes, onde as amostras foram irradiadas no comprimento de onda de 488 nm usando um laser contínuo (CW) de argônio, variando-se a potência de irradiação e o tempo de exposição. Nesse caso, foram observados a fotocristalização, onde a presença da fase de Te hexagonal foi observada por espalhamento Raman e Difração de Raios X. Esses efeitos mostraram-se reversíveis com o tratamento térmico das amostras em temperaturas próximas de sua temperatura de transição vítrea (Tg) / Chalcogenide glasses base of tellurium is attracting great academic and technological interest due to their versatile optical properties, electrical and physical and chemical properties, allowing use in several areas of photonics. This thesis presents the study of crystallization kinetics and photoinduced phenomena in glass system Ge-Te-Ga. The compositions Ga20Ge10Te70 (GGT7) and Ga10Ge10Te80 (GGT10) were carried out study the crystallization induced by thermal treatments performed on glasses with particle size of 53 < x > 45 μm and a piece are analyzing the fraction crystallized. This analysis relies on the crystallization peaks, obtained with the Differential Scanning Calorimetry (DSC) technique. The curves of the crystallized fraction and decreased crystallization time with increasing heating rate. The calculation of the crystallized fraction was realized, first, by considering the 0peaks of crystallization. The activation energy from Kissinger, Ozawa, and Mahadevan Augis and Benett method was obtained and Avrami exponent, which provides information on the processes of nucleation and crystal growth for both compositions. The data showed high values of activation energy, interesting feature in applications where stability of the amorphous phase is required. In the second part of the work were produced thin films by Electron Beam Physical Vapor Deposition, using the vitreous compositions GGT7 and GGT10. The effects were evaluated in the photoinduced films, where the samples were irradiated by wavelength of 488 nm using a continuous Argon laser (CW), varying the power of irradiation and exposure time. The photocrystallization were observed, where the presence of hexagonal Te phase were observed by Raman scattering and X-ray diffraction These effects were shown to be reversible by thermal treatment of the samples at temperatures close to their glass transition temperature (Tg)

This work presents photophysical and nonlinear optical properties of a novel Cd 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (CdOtBPPc) and compared with those of Pb 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (PbOtBPPc). For both the CdOtBPPc and PbOtBPPc, third order imaginary susceptibility and second order hyperpolarizability values were found to be within the limit set for good optical limiters. The Pcs were embedded in poly (methyl methacrylate) (PMMA) and poly(bisphenol A carbonate) (PBC) as thin films. The optical limiting values of the Pcs once embedded in film were found to be greatly improved and the limiting intensity of each film was well below the maximum threshold. Both PbOtBPPc and CdOtBPPc showed better optical limiting when embedded in PBC compared to PMMA. CdOtBPPc shows better nonlinear optical behaviour than PbOtBPPc in solution and as thin films, even though the former is aggregated in solution. Novel phosphorus triazatetrabenzcorroles (TBC) tetrasubstituted at the α- and β- and octa substituted at the β- positions of the peripheral fused benzene rings with t-butylphenoxy substituents were prepared and characterized. The effects of the substituents and the missing aza-nitrogen on the electronic structures and optical spectroscopy are investigated with TD-DFT calculations and MCD spectroscopy. The optical limiting properties were investigated to examine whether the lower symmetry that results from the direct pyrrole-pyrrole bond and hence the permanent dipole moment that is introduced result in higher safety thresholds, relative to the values that have been reported for phthalocyanines. The suitability of the compounds for singlet oxygen applications has also been examined. Novel phosphorus phthalocyanines, analogous to the triazatetrabenzcorroles were also investigated. Due to their high photodegradation quantum yield however, only the fluorescence quantum yields and lifetimes were able to be determined.

Neutron reflectivity offers the opportunity for non-destructive characterisation of buried polymer interfaces. Specular neutron reflectivity is commonly used to characterise the structure of conjugated polymer interfaces found in organic electronic devices. However, detecting specularly reflected neutrons only allows the measurement of the root-mean-square (RMS) roughness of the interface averaged over a macroscopic lateral distance. There are two contributions to the RMS roughness of a polymer/polymer interface; i) the so-called 'intrinsic interfacial width' due to mixing of the polymers at a molecular level and ii) lateral roughness due to deviations of the interface position from the plane of the substrate. In this work a numerical model is developed to analyse experimental off specular reflectivity. The model is based on the distorted wave Born approximation (DWBA). Specular and off specular neutron reflectivity data is collected from a model conjugated polymer/amorphous polymer interface (poly(9,9-dioctylfluorene) (F8) on deuterated PMMA) and a conjugated poly- mer/fullerene interface (poly(3-hexylthiophene) (P3HT) polymer on [6,6]-phenyl C61-butyric acid methylester (PCBM)). This allows probing of the structure in the plane of the interfaces to distinguish the intrinsic interfacial width from the lateral roughness. The structure of the F8/dPMMA interface is studied by systematically varying the film thickness, which strongly impacts on the amplitude of the lateral interface roughness, and allows more complete analysis of the relative contributions of intrinsic mixing and lateral roughness. For comparison off specular measurements on amorphous/amorphous polymer (PMMA/polystyrene) interfaces are performed, which have been studied previously using specular neutron reflectivity and self consistent held theory. Fitting specular reflectivity using standard techniques and off specular reflectivity data using the model developed allow intrinsic and lateral roughness contributions for the F8/dPMMA system to be separated by direct measurement. The P3HT/PCBM interface exhibits no lateral roughness as the materials are found to be miscible.

No description available.

In recent years, portable devices and larger display are the trend of market, so transparent conducting oxides (TCO) draw a considerable interest due to their unique characteristics and essential role in the technology of flat panel display. Indium tin oxide (ITO) is one of the most widely used TCO in the application of display technology. In this work, properties of ITO thin film as a function of dopant ratio and density of sputtering targets had been done. It is found that the mechanism of oxygen vaccines is more dominated in electrical conduction than dopant concentration. Meanwhile, the conductivity of ITO thin film depends on the sputtering condition than the target itself. Annealing process is one of the ways to enhance the optical properties of ITO thin film. This process can change the crystal structure of film from amorphous to crystalline but limited by the presence of the oxygen. Apart from the transitional single layer of ITO thin film, a modified structure had been done by inserting a thin layer of metal (Al/Ag) into ITO which provides a highway for carrier transparent. A modified structure with Ag is successfully demonstrated and well agrees with the theory. OLED application was also done by using sandwich structure. The key of sandwich structure is the metal layer, non-reactive and highly conducting material should be selected. Upper and bottom TCO layers are purpose-built for application without affect the properties of structure. This structure also shows more robust on the flexible substrate than single layer ITO.

Thesis (MTech (Science))--Peninsula Technikon, Cape Town, 1998 / The chemical system, Si < >1 Pd 1Cr, was investigated to study the formation of CrSil on polycrystalline PdlSi, formed on Si<IOO> and epitaxial PdlSi formed on Si<lll>. To ascertain the reaction mechanism during the formation, tantalum was used as an inert marker, since it does not participate in the reaction and is readily measured by Rutherford Backscattering Spectrometry (RBS). This investigation was performed in two parts. In the first part, the tantalum was inserted in the PdlSi layer to determine which species; palladium or silicon diffuses during CrSil formation. In the second part, the marker was inserted in the CrSiI layer to determine whether chromium or silicon moves. In addition, the effect of marker thickness on the growth of CrSiI was investigated. The samples were prepared by electron gun evaporation in vacuum, the elements being deposited on the particular silicon substrates. This was followed by the thermal treatment of the samples at temperatures of 400,425,450,475,500 and 550°C. Normal and dynamic Rutherford backscattering spectrometry was used to characterize the thin film structures. If the marker, when inserted in the PdISi layer, should move towards the PdISi I CrSil interface then, the formation of CrSil would be due to the dissociation of Pd2Si. In this case PdlSi dissociates into Pd and Si and the Si diffuses to the interface of CrSi2 and Cr to form CrSil, whereas the Pd diffuses to the Si < > I Pd2Si interface to regrow PdISi. However, if the marker position remains constant with respect to the Pd2Si layer it can be concluded that the formation of CrSiI is due to the movement of Si from the substrate to the interface of CrSi2 and Cr to form CrSiI. If the marker when inserted in the CrSi2 should move towards the sample surface then the chromium diffuses to the interface ofCrSi1 and PdlSi to react with the silicon, forming CrSi2 .

Charge transport in semiconductor channels of organic field-effect transistors (FETs) depends largely on the molecular ordering of organic semiconductor molecules. This is particularly demanding for polymer-based FETs, where channel semiconductors are non-molecular in nature, and generally form semiconductor films of low crystallinity. As a result, great theoretical and practical interests have been directed towards facile solution processes that can transform a low molecular weight (MW) and low mobility conjugated polymer into a high crystalline order and high-mobility semiconductor. This research focuses on developing effective strategies for achieving high mobility as well as other desirable FET properties through properly controlling the morphology and molecular ordering of conjugated polymer channel layers. The relationships between morphologic/microstructural properties of the polymer semiconductor films and charge transport characteristics in the films are systematically investigated and elucidated. The purpose of this work is to achieve high performance solution-processed polymer FETs with high mobility, excellent ambient stability, and performance uniformity that display practical significance for application in next-generation electronics. In the first part of this thesis, functionalization of the gate dielectric surface by grafting highly ordered and dense coverage of hybrid silane self-assembled monolayers (SAMs) is discussed. A two-step solution-processed method using a combination of trichlorooctadecylsilane (OTS-18) and trichlorooctylsilane (OTS-8) has been developed to create high-performance hybrid dual-silane SAM on the surface of silicon dioxide (SiO2), thus enabling the achievement of both high field-effect mobility and current on/off ratio, together with other desirable FET properties. The hybrid SAM approach is also adopted for attaining high performing polymer FETs using a different SAM agent combination of phenyltrichlorosilane (PTS) and OTS-18. With the progress in functionalizing the surface of gate dielectric insulator by two-step grafting SAMs, the advancement in enhancing the crystalline structural order of the polymer channel layer is highlighted. This was realized by the incorporation of polar insulator of polyacrylonitrile (PAN) into the polymer semiconductor solution at appropriate loadings, enabling the formation of excellent semiconductor films with high crystalline order. PAN serves as an efficient mediating medium for the crystallization of polymer semiconductor, leading to the creation of large crystalline domains within the PAN matrix. A 1̃0-nm thick semiconductor layer with richer semiconductor crystalline domains is constructed near the vicinity of the gate dielectric surface, facilitating efficient charge conduction in the channel semiconductor. Enhancements in field-effect mobility by as much as about one order in magnitude and current on/off ratio of two to three orders in magnitude have been realized in polymer FETs. PAN incorporation also dramatically enhances the stability and processability of semiconductor solutions, enabling rapid fabrication of channel semiconductors in polymer FETs via common graphic art printing techniques such as inkjet printing for practical adoption. Another unique facile solution process which transforms a lower-MW and low-mobility conjugated polymer, e.g., diketopyrrolopyrrole-dithienylthieno[3,2-b] thiophene (DPP-DTT), into a high crystalline order and high-mobility nanowire network for high performance polymer FETs has been also developed in this work. This approach involves solution fabrication of a channel semiconductor film using a lower MW DPP-DTT/polystyrene blend system. With the help of cooperative shifting motions of polystyrene chain segments, an interpenetrating nanowire semiconductor network is readily self-assembled and crystallized out in the polystyrene matrix, and thereby providing significantly enhanced mobility (over 8 cm2 V-1 s-1) and current on/off ratio (107). Finally, the concept of generating polymer nanowire network in the effective photoactive channel is extended for the development of highly sensitive near-infrared (NIR) organic phototransistors (OPTs). The NIR-OPTs based on DPP-DTT nanowire network exhibit high responsivity of 2̃46 A W-1 under an NIR illumination source with the wavelength of 850 nm at a low intensity of ̃0.1 mW cm-2. This value is over one order in magnitude higher than that of the structurally identical planar DPP-DTT thin film based OPTs. The high performance of the nanowire network-based phototransistors is attributed to the excellent hole transport ability, reduced density of the structural defects in the polymer nanowire network, and improved contact at the channel layer/electrode interfaces. The high sensitivity and low cost solution-fabrication process render this OPT technology appealing and practically viable for application in large area NIR sensors.