This thesis reports on the design and fabrication of micro-electro-mechanical (MEM) resonators on silicon that are piezoelectrically-transduced for operation in the very high frequency (VHF) range. These devices have a block-type or beam-type design, and are designed to resonate in their in-plane and out-of-plane bulk extensional modes. Two piezoelectric materials were taken into consideration, zinc-oxide (ZnO) and lead-zirconate-titanate (PZT). The resonators are fabricated on silicon-on-insulator (SOI) wafers and the metal/piezo/metal stack of layers forming the device is built and patterned on the device layer silicon via photolithography techniques, RF sputtering (for the piezo-layer) and electron-beam evaporation (for the metal layers). The designing aspect involved ANSYS simulations of the mode-shapes and estimation of frequencies, and these have correlated well with experimental results. Devices with RF sputtered ZnO were successfully fabricated and tested to give high quality factors at reasonably high frequencies. A gold ground plane was implemented to reduce the feed-through level and increase the signal-to-noise ratio. Extensive characterization of PZT was also done as a replacement for ZnO, as the former material has a much higher piezoelectric coefficient (~20X that of ZnO) and can therefore extend the operation of these MEM resonators into the UHF range. Although the basic design of the device remains the same, incorporation of PZT complicates the process flow considerably with respect to the chemistry now involved with the patterning of different layers. The frequency response for ZnO-based resonators as well as all the characterization data for PZT has been reported.

The aim of this thesis work was to develop magnetoelectric (ME) composites consisting of piezoelectric and magnetostrictive components. The piezoelectric constituent was selected as a PZT ceramic modified by strontium, bismuth and manganese. The magnetostrictive phase was nickel ferrite (NF) ceramic doped by cobalt, copper and manganese. The properties of component phases were optimized in order to enhance the ME effect in the composite. In the first part of the thesis, effects of sintering temperature on the dielectric and piezoelectric properties of PZT and on the electrical and magnetic properties of NF ceramics were investigated in the temperature range covered from 1150 to 1250 &deg / C. The best piezoelectric properties in PZT were attained at 1250 &deg / C. At this sintering temperature, values of piezoelectric strain coefficient, dielectric constant, and electromechanical coupling coefficient were 434 pC/N, 1320 and 0.48, respectively. NF ceramics showed poor densification / 80 %TD was attained at 1250 &deg / C. In order to obtain higher densities in ferrites, Bi2O3 was used as a sintering aid. Addition of Bi2O3 enhanced densification up to 97 %TD, and improved electrical and magnetic properties of ferrites. Highest DC-resistivity of 1.15*10^8 ohm-cm and highest magnetostriction of ~26 ppm were attained in NF ceramics doped with 1 wt% Bi2O3. In the second part of the thesis, ME composites were manufactured either as bulk composites or as laminated composites. The efficiency of different composite types was evaluated in terms of voltage output in response to the applied magnetic field. Higher outputs were observed in laminated composites.

Oxide nanowire arrays are playing an important role in energy sciences nowadays, including energy harvesting, energy storage, and power management. By utilizing a wet chemical growth method, we demonstrated the capabilities of synthesizing density controlled vertical ZnO nanowire arrays on a general substrate, optimizing the aspect ratio of the vertical ZnO nanowire arrays guided by a statistical method, epitaxially growing patterned vertical ZnO nanowire arrays on inorganic substrates, epitaxially growing patterned horizontal ZnO nanowire arrays on non-polar ZnO substrates, and the lift-off of the horizontal ZnO nanowire arrays onto general flexible substrates. In addition, single crystalline PbZrxTi1-xO3 (PZT) nanowire arrays were epitaxially grown on conductive and nonconductive substrates by hydrothermal decomposition. Beyond that, based on the as-synthesized ZnO nanowire arrays, we demonstrated multilayered three dimensionally integrated direct current and alternating current nanogenerators. By integrating a ZnO nanowire based nanogenerator with a ZnO nanowire based nanosensor, we demonstrated solely ZnO nanowire based self-powered nanosystems. Also, utilizing a commercial full-wave bridge rectifier, we rectified the alternating output charges of the nanogenerator based on PZT nanowire arrays, and the rectified charges were stored into capacitors, which were later discharged to light up a laser diode (LD). In addition, blue/near-ultraviolet (UV) light emitting diodes (LED) composed of ordered ZnO nanowire arrays on p-GaN wafers were presented.

Current MEMS development is driven by the need to develop various 'Miniaturized Total Chemical Analysis Systems ([mu]TAS), biological and chemical sensing, drug delivery, molecular separation, microfiltration, amplification, and sequencing systems. In this work, the use of flexural plate wave devices as an actuator has been investigated.This research was done with the aim of developing a platform to build FPW devices for use in System-On-Chip applications. It is well known that acoustic forces generated by a flexural plate wave (FPW) device can cause fluid motion, by the principle of acoustic streaming. Also the proven ability of FPW devices to cause mixing, filtration and to work as a chemical-biological sensor can be used towards building a micromachined [mu]TAS. The effects of the IDT finger width, spacing, aperture, membrane thickness, and driving conditions on the device performance was studied to understand the impact of IDT design on device performance.

In recent years, research on development of chemical, biological and hazardous gas sensors for homeland security have attracted great deal of interest. Actuators possessing high sensitivity, easy fabrication techniques and excellent integration compatibility are in great demand. Towards this need, the development and characterization of improved sol-gel processing for in-house fabrication of highly sensitive and reliable Flexural Plate Wave (FPW) device was pursued This work focuses on an experimental design approach to improve texture and morphology of PZT thin film by systematically controlling the spin, pyrolysis and anneal cycles. The process alterations resulted in an 8-fold increase in the relative intensity of perovskite (111) phase, which consequently yielded a two fold improvement in remnant polarization and coercive field compared to industry recommended processes.

Laser micromachining has become increasing prominent in various industries given its speed, lack of tool wear, and ability to create features on the order of micrometres. Inherent stochastic variations from thermal ablation along with detrimental heat effects, however, limit the feasibility of achieving high precision. The high number of control parameters that make laser micromachining versatile also hinders optimization due to high exploration time. The introduction of high intensity nonlinear ablation leads to more precise cuts but at a much higher, often restrictive, cost. The work here shows that by combining an imaging technique frequently used in ophthalmology called optical coherence tomography (OCT) with a machining platform, in situ observation of ablation can be made. This combination, known as in-line coherent imaging (ICI), allows information to be gathered about the dynamics of the ablation process. Experimental results show that quality cutting of silicon can be achieved with thermal ablation and at a wavelength of 1070 nm. This result is surprising as silicon absorbs this wavelength very weakly at room temperature. It is shown here that a nonlinear thermal dependence in absorption allows a cascaded absorption effect to enable machining. With the aid of ICI, the model shown here is able to accurately predict the thermal ablation rate and help understand the ablation process. The high quality cutting achieved allows for a more cost efficient alternative to current techniques using ultraviolet diode-pumped solid state (UV DPSS) systems. Where thermal effects such as heat-affected zones (HAZ) cannot be overcome, high intensity nonlinear ablation allows the processing of lead zirconate titanate (PZT) for high frequency arrays (used in ultrasound applications) at speeds two orders of magnitude greater than found in the literature, and potential feature sizes (< 100 µm) in polymethyl methacrylate (PMMA) unachievable by thermal ablation. The ablation mechanism here is Coulombic explosion (CE), which is a non-thermal process. Coupled with demonstrated manual and automatic feedback abilities of ICI, the processes shown here may open up new avenues for fabrication. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-05-31 15:02:55.547

Piezoelectric materials have numerous applications like high temperature accelerometers, pressure, flow and NDT transducers, acoustic emission, ultrasonic cleaning, welding, high voltage generators, medical therapy etc. The commonly used piezoelectric material, PZT continues to dominate the commercial market for piezoelectric actuators applications. The primary limitations of PZT are the lower Curie temperature TC <390oC and rapid thermal degradation avobe 200oC. Continuing efforts are focused on the development of piezoelectric materials suitable for high temperature applications >200oC. These materials will be very useful for making sensors for space exploration, oil and geothermal well drilling tools, oil & gas pipeline health monitoring and automotive smart brakes. Recently material based on (1-x)Bi(Me)O3-xPbTiO3 developed with TC~460oC, and d33~500 pC/N compared to TC~390oC and d33~220 pC/N of pure PZT. Enhanced room temperature properties and higher transition temperature makes this material interesting for further investigation as a high temperature piezoelectric material. Reliability of technological piezoelectric devices is a major concern for their applications. Many piezoelectric materials undergo a process of aging, associated with a spontaneous decrease of electromechanical properties. In the current work thermal degradation and aging behavior of high temperature piezoelectric material BSPT was evaluated and compared with the commonly used PZT.

Zugl.: Ilmenau, Techn. Universiẗat, Diss., 2007.

O processo de microfabricação por coextrusão (MFCX) foi estudado a fim de obter compósitos de zirconato titanato de chumbo (PZT), por meio da fabricação de fibras. O princípio desta técnica é a redução dimensional de um pré-formato cilíndrico formado pelos materiais já nas posições e proporções desejadas ao longo da secção transversal em filamentos mais finos, através da passagem por um molde. Tais componentes devem possuir o mesmo comportamento reológico para que possam fluir juntos, fazendo com que o pré-formato sofra apenas uma redução da secção transversal ao passar pela boquilha. Entre tais componentes, o material principal é uma suspensão concentrada de pó de PZT e polietileno de baixa densidade (PEBD). Este fornece a característica termoplástica para a mistura e auxilia na resistência mecânica a verde. Existe ainda, o material provisório, o qual já havia sido estudado e foi trocado de negro de fumo (NF) para celulose microcristalina (MCC), uma vez que com o uso de NF, um resíduo inorgânico foi verificado após a etapa de retirada do ligante o qual poderia influenciar na microestrutura e nas propriedades piezoelétricas do PZT, causando queda na polarização obtida. Para caracterizar a reologia das misturas, foram usados pré-formatos cilíndricos formados por metades de diferentes materiais com secção transversal semicircular, tendo como composição padrão 58 vol. % de PZT + PEBD. Já os materiais provisórios foram estudados nas seguintes composições: 25 vol. % de NF + PEBD, 31 vol. % de MCC + PEBD e 41 vol. % de MCC + ácido esteárico (AE) + PEBD. Os filamentos obtidos após a passagem pelo molde foram caracterizados e posteriormente comparados entre si, a fim de verificar a influência do material fugitivo e dos aditivos na microestrutura. A capacidade do pré-formato de manter o equilíbrio das dimensões e proporções após a coextrusão também foi verificada por meio de análise de imagem. Verificou-se que as misturas de MCC + PEBD e PZT + PEBD não foram capazes de fluir concomitantemente mesmo quando ambas apresentavam a mesma viscosidade. Assim, a reologia foi estudada considerando não apenas a viscosidade, mas também as propriedades de deslizamento na parede do molde para este sistema. Depois de modificações na composição e parâmetros do processo, foi obtida uma equivalência adequada entre os materiais, concluindo que a coextrusão de dois materiais compondo um pré-formato de seção transversal complexa pode ser bem-sucedida quando as mesmas velocidades de deslizamento na parede e as mesmas viscosidades corrigidas puderem ser encontradas para a mesma taxa de cisalhamento. / The process of microfabrication by coextrusion (MFCX) was investigated to obtain composites of lead zirconate titanate (PZT), through the fabrication of PZT fibers. The principle of this technique is the reduction of a preform formed of concentrated suspensions in the positions and proportions desired, into filaments thinner after passing through a die. Such materials must have the same rheological behavior so they can flow together, making the preform to suffer only a reduction in the cross section to pass through the capillary. The main material was a concentrated suspension of PZT powder and low density polyethylene (LDPE), which provides the thermoplastic characteristic for the mixture and improves the mechanical strength at green state. In the other hand, the fugitive material was changed from carbon black (CB) into microcrystalline cellulose (MCC), once with the use of CB, an inorganic residue was found after the step of debinding. Furthermore, the CB impurities could influence the piezoelectric properties of PZT, causing a drop in the polarization measured. The rheological characterization employed preforms with cross section geometry of a half moon, with a standard composition of 58 vol. % PZT. Meanwhile, the fugitive materials were studied using the following compositions: 25 vol. % CB + LDPE, 31 vol. % MCC + LDPE and 41% vol. MCC + stearic acid (ST) + LDPE. The filaments obtained were characterized and then compared to verify the influence of the fugitive material and the additives on the microstructure. The ability of the preform to maintain the balance of the dimensions and proportions after co-extrusion was also verified by image analysis. It was found that mixtures of MCC + LDPE and CB + LDPE were not able to flow simultaneously. Thus, the rheology was studied considering not only the viscosity but also the properties of slip on the wall of the capillary die. After changing the composition and process parameters, a good match between the materials could be obtained, which allowed the coextrusion in the shape of half moon, getting a constant and well defined reduction of the diameter.

Made available in DSpace on 2016-06-02T20:34:07Z (GMT). No. of bitstreams: 1 1946.pdf: 9292037 bytes, checksum: 119351fd8e0cd7b745977db6fd72ec7c (MD5) Previous issue date: 2007-09-27 / Universidade Federal de Sao Carlos / This work presents a systematic study of synthesis and characterization of ferroelectric nanoislands. Generally three methods were had been studied: polymerized complex method (MPC), hydrothermal synthesis and nonaqueous synthesis. In order to optimize the formation of nanoislands we realized studies about influence of some experimental parameters. When we used MPC the concentration of metallic cátions (Pb2+, Zr4+ and Ti4+) in the polymeric resin, influence of the type calcination (using microwave and conventional oven), the citric acid - metallic cátion ratio (AC:Metal) and the resins deposition method were varied. The results showed that using the spin-coating deposition onto Si (100) substrate, the dilution of the polymeric resin proportionate samples with of distinct particle concentrations. Some of these regions with nanoislands. With the increase of ratio AC: Metal we had the formation of continuous films. The samples prepared by immersion method showed that it is possible the formation of nanoislands with uniform size and distribution by MPC. Tests in MgO and STO substrates were also accomplished based on the optimization discussed above. Tests with one layer indicated only the presence of PZT tetragonal phase. Moreover the optimized immersion conditions lead the formation of a continuous film along the MgO substrate. The sample obtained onto STO substrate presented agglomerated regions. Also hydrothermal synthesis was used to produce PZT nanoparticles. However, even with the variation of the synthesis conditions PZT powders were obtained in a micrometric scale. On the other hand, the nonaqueous route produced a low cristallinity PZT precursor, with was crystallized at lower temperatures than those reported in the literature. Besides, BaTiO3 was also studied. In this case the samples were deposited by immersion and spin-coating. The samples obtained by immersion did not present the formation of nanoislands but regions with agglomerated particles. The viscosity and concentration of organic material were investigated accomplished aiming the formation of films with the thinnest thickness possible to the samples obtained by spin-coating. The formation of continuous films was verified and in some of them the formation of pores was observed. The formation of micrometric islands was observed at higher temperatures. / Este trabalho apresenta um estudo sistemático sobre a síntese e caracterização de nanoilhas ferroelétricas. De modo geral três métodos foram estudados: o método de polimerização de complexos (MPC), a síntese hidrotermal e a síntese não aquosa. A fim de otimizar a formação das nanoilhas foi realizado um estudo sobre a influência de alguns parâmetros experimentais. No caso do MPC foram variadas, a concentração de cátions metálicos (Pb2+, Zr4+ e Ti4+) na resina polimérica, influência da calcinação (utilizando-se microondas e forno convencional) e o método de deposição das resinas. Os resultados obtidos mostraram que utilizando-se a deposição por spin-coating em substratos de Si(100), a diluição da resina polimérica proporcionou amostras com regiões de distintas concentrações de partículas. Em determinadas regiões as nanoilhas foram observadas. Com o aumento da relação AC:Metal foram obtidos filmes contínuos. As amostras preparadas por imersão mostraram que é possível a formação de nanoilhas com tamanho e distribuição uniforme utilizando-se o MPC. Foram realizados também testes de deposição por imersão em substratos de MgO e STO, baseando-se na otimização acima discutida. Testes com uma camada de resina apontaram a presença da fase de PZT tetragonal. No entanto as condições utilizadas de imersão levaram a formação de um filme continuo ao longo do substrato de MgO. Já a amostra obtida em substrato de STO apresentou aglomerados. Também utilizou-se a síntese hidrotermal para a produção de nanopartículas de PZT. Entretanto, mesmo com as variações das condições de síntese os pós de PZT foram obtidos em escala micrométrica. Por outro lado com a síntese não aquosa produziu-se um precursor de PZT de baixa cristalinidade e este foi cristalizado a temperaturas menores que aquelas reportadas na literatura. Além disso, um outro material aqui estudado foi o BaTiO3, neste caso foram obtidas amostras depositadas por imersão e por spincoating . As amostras obtidas por imersão não apresentaram a formação de nanoilhas e sim de regiões com partículas aglomeradas. A viscosidade e concentração de material orgânico foram investigadas visando a formação de filmes com as menores espessuras possíveis para as amostras obtidas por spin-coating . Verificou-se a formação de filmes contínuos e em alguns deles observou-se a formação de poros. Os tratamentos térmicos em altas temperaturas possibilitaram a formação de ilhas micrométricas.