Shear-mode thin film bulk acoustic resonator (TFBAR) devices with c-axis tilted AlN films are fabricated for the application of liquid sensors. To fabricate shear-mode TFBAR devices, the off-axis RF magnetron sputtering method for the growth of piezoelectric AlN thin films is adopted and influences of the relative distance and the sputtering parameters are investigated. The shrar-mode phenomenon of a TFBAR results from the tilted crystalline orientation of AlN thin films. In this thesis, the AlN thin films are deposited with tilting angles of 15¢X and 23¢X, set by controlling the deposition parameters. The properties of the AlN thin films are investigated by X-ray diffraction and scanning electron microscopy. The frequency response is measured using an HP8720 network analyzer and a CASCADE probe station. The frequency response of the TFBAR device with 23¢X tilted AlN thin film is measured to reveal its ability to provide shear-mode resonance. The resonance frequencies of the longitudinal and shear modes are 2.07 GHz and 1.17 GHz, respectively. To investigate the sensing characteristics of TFBAR, two basic experiments of mass and liquid loading are carried out. The sensitivities of the longitudinal and shear modes to mass loading are calculated to be 2295 Hz cm2/ng and 1363 Hz cm2/ng with the mechanical quality factors of 588 and 337, respectively. However, the mechanical quality factors of the longitudinal mode of TFBAR without and with a liquid loading decreased from 588 to 0, whereas those remain almost the same for the shear mode under liquid loading. The sensitivities of the longitudinal and shear modes are calculated to be 0 and 17.88 Hz cm2/£gg for liquid loading.

A novel liquid sensor is designed and fabricated by using thin film bulk acoustic resonator (TFBAR) devices with c-axis 23¢X-tilted ZnO films. To fabricate TFBAR devices, the off-axis RF magnetron sputtering method for the growth of piezoelectric ZnO thin films is adopted. The influences of the relative distance and sputtering parameters are investigated. In this report, the piezoelectric ZnO thin films with tilting angle of 23¢X are set by controlling the deposition parameters. The properties of the c-axis 23¢X-tilted ZnO thin films are investigated by X-ray diffraction and scanning electron microscopy. The frequency response is measured using an HP8720 network analyzer with a CASCADE probe station. The TFBAR devices with 23¢X-tilted ZnO thin films display shear and longitudinal resonant modes at 752.75 MHz and 1.70 GHz, respectively. The mechanical quality factors (QL for longitude mode and QS for shear mode) are thus the important parameters of dual-mode TFBAR devices used in liquid environments. QL decreased from 545 to 0 upon in liquid loading, whereas QS remained almost unchanged at 296 in all environments. Moreover, the sensitivity of the shear mode to liquid loading is calculated to be 13 Hz cm2/£gg.

Ti thin films were deposited by a radio frequency ion-beam sputtering system. Deposition resulted from sputtering a Ti target (99.995%) with an Ar ion beam. Epitaxial TiO thin films with different orientations, which came from oxidizing Ti thin films, were prepared on single-crystal NaCl substrate. The formation of epitaxial TiO2 thin films (anatase or rutile phase) by oxidation of epitaxial TiO thin films was investigated. The composition, microstructure, and orientation relationships between interfaces were analyzed by TEM and Fourier transformation in the present report. Epitaxial TiO thin films with different orientations were prepared on single-crystal NaCl substrate in the present study. The formation of epitaxial TiO2 thin films (anatase or rutile) by oxidation of epitaxial TiO thin films, which were first grown on different NaCl surfaces, was investigated. The composition, microstructure, and orientation relationships between interfaces were analyzed by TEM and Fourier transformation in this report. The TiO to anatase phase transformation has been studied by transmission electron microscopy in this Article. It is shown that prior formation of TiO from Ti film can induce the formation of anatase by thermal oxidation in air, otherwise only rutile is formed. Ti film deposited on the NaCl (001) surface is induced to form epitaxial TiO film by thermal oxidation in air. Further thermal oxidation in air partially transformed TiO into anatase (A) with a parallel orientation relationship of {200}A // {200}TiO. Detailed analysis of the lattice fringes image of the specimen reveals the presence of very high density of misfit dislocations. The TiO to anatase transformation is reversible as further annealing in a vacuum can turn the anatase back into TiO and eliminates the misfit dislocations. The transformation is analyzed in terms of the crystal structure, orientation relationship, and the dislocation distribution, which show that the TiO to anatase transformation is due to the close similarity between their structures. (Chapter 1) The anatase TiO2 (001) surface was shown to have superior photoreactivity. Epitaxial anatase (001) films used to be grown on single-crystal SrTiO3 and LaAlO3 substrates. It is shown in this report that these films can be grown also on the NaCl substrate, which is much cheaper and easily prepared. Epitaxial TiO (001) films were first grown on the NaCl (001) substrate. By testing the TiO-to-anatase transformation over temperature and time ranges, an epitaxial anatase (001) film was prepared by simple thermal oxidation in air. The formation of a single-variant anatase (001) film instead of a multiple-variant film is discussed in this report. (Chapter 2) An epitaxial rutile (100) thin film has been grown on NaCl substrate instead of other more expensive substrates. An epitaxial TiO (111) thin film with minor Ti phase was first deposited on the NaCl (111) surface by thermal evaporation. It was then transformed into the epitaxial rutile (100) thin film by subsequent thermal oxidation in air. TEM was used to analyze the phases and the orientation relationship. Our previous result showed that an epitaxial anatase (001) film was formed on the NaCl (001) surface in a similar process. The substrate-dependent formation of different TiO2 phase is also discussed in terms of the mismatch of the interfaces. (Chapter 3)

Conductive thin films of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) were created via layer-by-layer assembly. The PEDOT-PSS was used in an aqueous solution as an anionic polyelectrolyte, with both linear and branched polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH) in the positive aqueous solution. The electrical conductivity was varied by altering pH, concentration, polyelectrolyte, and doping the PEDOT with dimethylsulfoxide (DMSO). The most conductive 12BL samples were doped with 1wt% DMSO and have a sheet resistance of approximately 8kΩ/□. Despite exhibiting good initial conductivity, these PEDOT based thin films degrade under ultraviolet (UV) exposure. UV absorbing nanoparticles were added into the cationic solution in an effort to reduce UV sensitivity. The final bilayers of the films contained either colloidal titanium dioxide (TiO2) or carbon black (CB) and the films were exposed to a 365nm UV-light with an intensity of 2.16mW/cm2 for 9 days. The UV light at this intensity correlates to approximately four years of sunlight. The initial sheet resistances for all samples were similar, but the UV-degradation was reduced by a factor of 5 by utilizing TiO2 and CB in the final bilayers. In addition to being the most conductive after UV exposure, the TiO2 containing film was also 27% more optically transparent than the pure PEDOT films. These additional UV-absorbing nanoparticles extend the operational life of the PEDOT films and, in the case of TiO2, do so without any reduced transparency.

Since the early 1960s, Abrikosov-Gorkov theory has been used to describe superconductors with paramagnetic impurities. Interestingly, the density of states resulting from the theoretical framework has to date only been known approximately, as a numeric solution of a complex polynomial. An analytical solution to the theory was discovered and applied to extract the spin polarization from the tunneling conductance of superconducting aluminium with 3-dimensional (3-D) amorphous (a-) gadoliniumxsilicon1-x (GdxSi1-x) as a counter electrode (Al/Al2O3/a-GdxSi1-x planar tunnel junction measured at T = 25 mK and H less than or equal to 3.0 T) in the quantum critical regime (QCR). The analytical solution is valid in the whole regime of Abrikosov-Gorkov theory independent of the presence of an energy gap. Applying the spin polarized Abrikosov-Gorkov theory to describe aluminium gives a larger spin polarization in GdxSi1-x than the spin polarized Bardeen-Cooper-Schrieffer (BCS) theory. The purpose of this study is to extract polarization at various applied magnetic fields, but no specific relationship between the two could be determined. Results obtained shows a transition from a superconductor with a gap to a gapless superconductor in varying external magnetic fields was observed. To improve understanding of GdxSi1-x near the metal-insulator transition (MIT) and compare it with prior work, the initial experimental attempts to investigate the transport property of GdxSi1-x near the MIT in the 2-dimensional limit are presented. A low temperature ultra high vacuum quench condensation system was used to make thin films of GdxSi1-x and in-situ measurements were performed. The transport properties for different values of x and thicknesses were measured for T = 4.2 K to ~10 K. In addition to other possible causes, the uncertainty in the electron impact emission spectroscopy (EIES) appeared to be a major reason behind the observed error in x when gadolinium and silicon are co-evaporated. The problems faced during the co-evaporation are also discussed.

A superconducting microwave cavity has been designed to test advanced materials for use in the accelerating structures contained within linear colliders. The electromagnetic design of this cavity produces surface magnetic fields on the sample wafer exceeding the critical limit of Niobium. The ability of this cavity to push up to 4 times the critical field provides, for the first time, a short sample method to reproducibly test these thin films to their ultimate limit. In order for this Wafer Test cavity to function appropriately, the large sapphire at the heart of the cavity must have specific inherent qualities. A second cavity was constructed to test these parameters: dielectric constant, loss tangent, and heat capacity. Several tests were performed and consistent values were obtained. The consequences of these measurements were then applied to the Wafer Cavity, and its performance was evaluated for different power inputs. The Q_0 of the cavity could be as low as 10^7 because of the sapphire heating, therefore removing the ability to measure nano-resistances. However, with additional measurements in a less complex environment, such as the Wafer Test Cavity, the Q_0 could be higher than 10^9.

The thermal conductivity of PMMA films with thicknesses from 5 to 50 nanometers and layered over a treated silicon substrate is explored numerically by the application of the reverse non-equilibrium molecular dynamics (NEMD) technique and the development of a coarse-grained model for PMMA, which allows for the simulation time of hundreds of nanoseconds required for the study of large polymer systems. The results showed a constant average thermal conductivity of 0.135 W/m_K for films thickness ranging from 15 to 50 nm, while films under 15 nm in thickness showed a reduction of 30% in their conductivity. It was also observed that polymer samples with a degree of polymerization equal to 25% of the entanglement length had 50% less thermal conductivity than films made of longer chains. The temperature profiles through the films thickness were as predicted by the Fourier equation of heat transfer. The relative agreement between the thermal conductivity from experiments (0.212 W/m_K for bulk PMMA) and the results from this investigation shows that with the proper interpretation of results, the coarse-grained NEMD is a useful technique to study transport coefficients in systems at larger nano scales.

Ni-Mn-Ga is a ferromagnetic shape memory alloy that can be used for future sensors and actuators. It has been shown that magnetic field can induce phase transformation and consequently large strain in stoichiometric Ni2MnGa. Since then considerable progress has been made in understanding the underlying science of shape memory and ferromagnetic shape memory in bulk materials. Ni-Mn-Ga thin films, however is a relatively under explored area. Ferromagnetic shape memory alloy thin films are conceived as the future MEMS sensor and actuator materials. With a 9.5 percent strain rate reported from magnetic reorientation, Ni-Mn-Ga thin films hold great promise as actuator materials. Thin films come with a number of advantages and challenges as compared to their bulk counterparts. While properties like mechanical strength, uniformity are much better in thin film form, high stress and constraint from the substrate pose a significant challenge for reorientation and shape memory behavior. In either case, it is very important to understand their behavior and examine their properties. This thesis is an effort to contribute to the literature of Ni-Mn-Ga thin films as ferromagnetic shape memory alloys. The focus of this project is to develop a recipe for fabricating NiMnGa thin films with desired composition and microstructure and hence unique properties for future MEMS actuator materials and characterize their properties to aid better understanding of their behavior. In this project NiMnGa thin films have been fabricated using magnetron sputtering on a variety of substrates. Magnetron sputtering technique allows us to tailor the composition of films which is crucial for controlling the phase transformation properties of NiMnGa films. The composition is tailored by varying several deposition parameters. Microstructure of the films has been investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Mechanical properties of as-deposited films have been probed using nano-indentation technique. The chemistry of sputtered films is determined quantitatively by wavelength dispersive X-ray spectroscopy (WDS). Phase transformation is studied by using a combination of differential scanning calorimetry (DSC), in-situ heating in TEM and in-situ XRD instruments. Magnetic properties of films are examined using superconducting quantum interface device (SQUID).

The article reports the lattice pattern self-assemble formation of polystyrene thin films. According to a simple observing device which using dark-field microscope, we collect a series of dynamitic image that air bubbles form a two-dimensionally or three-dimensionally ordered array in polymer film with Marangoni convection effect. In order to explain the array formation, we also provide two new models to discuss the phenomenon about 2D & 3D structure in this paper.

Aluminum nitride (AlN) thin films were deposited on SiO2/Si substrates using the reactive RF magnetron sputtering in this thesis. By means of the analysis of XRD, SEM, TEM and AFM, the optimal deposition conditions of highly C-axis oriented AlN films were obtained with RF power of 190W, sputtering pressure of 3mTorr, nitrogen concentration (N2/N2+Ar) of 30%, and substrate temperature of 400¢J. The characteristics of films annealed at temperature range from 600¢J to 1150¢J with N2 flow for 2 hours has been studied. Experimental results reveal that the films retain the high quality up to 800¢J. But when the temperature above 1000¢J, AlN films will be oxided to AlO:N. In addition, the interdigital transducers (IDTs) were fabricated on the films annealed at 800¢J for 2 hours to study the characteristics of SAW devices. The results show that the central frequency, insertion loss and phase velocity of SAW were 182.25 MHz, -12.95 dB and 5824 m/sec, respectively. At the same time, we try to match the impedence of devices and improve the frequency response by using a simulation program. After the impedence was matched, the insertion are not strongly improved but the frequency response and closed-in sidelobe rejection exhibit better. The effects of temperature on the SAW devices show that the central frequency almost does not shift when the temperature increases. But the insertion loss slightly increases with the temperature increased, the variation is about -0.02 dB/¢J.