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This work presents the low temperature plasma-enhanced atomic layer deposition (PE-ALD) of TiN, a promising plasmonic synthetic metal. The plasmonics community has immediate needs for alternatives to traditional plasmonic materials (e.g. Ag and Au), which lack chemical, thermal, and mechanical stability. Plasmonic alloys and synthetic metals have significantly improved stability, but their growth can require high-temperatures (>400 °C), and it is difficult to control the thickness and directionality of the resulting film, especially on technologically important substrates. Such issues prevent the application of alternative plasmonic materials for both fundamental studies and large-scale industrial applications. Alternatively, PE-ALD allows for conformal deposition on a variety of substrates with consistent material properties. This conformal coating will allow the creation of exotic three-dimensional structures, and low-temperature deposition techniques will provide unrestricted usage across a variety of platforms. The characterization of this new plasmonic material was performed with in-situ spectroscopic ellipsometry as well as Auger electron spectroscopy for analysis of TiN film sensitivity to oxide cross-contamination. Plasmonic TiN films were fabricated, and a chlorine plasma etch was found to pattern two dimensional gratings as a test structure. Optical measurements of 900 nm period gratings showed reasonable agreement with theoretical modeling of the fabricated structures, indicating that ellipsometry models of the TiN were indeed accurate.
We report on our progress towards the integration of nonreciprocal optical elements in, for example, an integrated optical waveguide isolator on conventional semiconductor photonic platforms. Our approach uses an evanescent interaction with a magneto-optic iron garnet upper cladding. Specifically, cerium- and bismuth- substituted yttrium and terbium iron garnets were investigated. Device fabrication incorporates RF sputtering, mask lift-off to form a grating for a quasi-phase-matched interaction and thermal anneal. A non-reciprocal polarisation-mode conversion was observed.
This study experimentally investigates the capabilities of iron-gallium nanowire arrays as artificial cilia transducers. The experiments are conducted with a custom manipulator device incorporated into the stage of a scanning electron microscope (SEM) for observation. Individual nanowires of varying size and composition are mechanically tested statically and dynamically to determine the elastic properties and failure modes. Entire arrays of close packed wires are mounted onto giant magnetoresistive (GMR) sensors to measure the coupled magnetic induction response resulting from bending the array. This data is compared with empirical and simulated results from previous macroscale research.
Packaging is a key issue for the effective working of an iron-gallium (Galfenol) nanowire acoustic sensor for underwater
applications. The nanowire acoustic sensor incorporates cilia-like nanowires made of galfenol, a magnetostrictive
material, which responds by changing magnetic flux flowing through it due to bending stress induced by the incoming
acoustic waves. This stress induced change in the magnetic flux density is detected by a GMR sensor. An effective
package should provide a suitably protective environment to these nanowires, while allowing sound waves to reach the
nanowires with a minimum level of attenuation. A bio-inspired MEMS package has been designed, analogous to a
human-ear cochlea for the nanowire acoustic sensor. In this paper, the process sequence for fabrication of the package is
presented. Unlike other microphones, the nanoacoustic sensor has been enclosed in a cavity to allow free movement of
the nanowires in a fluid medium. The package also ensures resisting ingression of sea water and salt ions to prevent the
corrosion of sensor components. The effect of package material on sensor performance was investigated by conducting
experiments on acoustic impedance and attenuation characteristics, and salt water absorption properties. The package
filled with silicone oil and molded with polydimethylsiloxane (PDMS) is observed to outperform other packages at all
frequencies by minimizing attenuation of the acoustic waves.
The development of packaging for an underwater acoustic sensor is a more complex task than package design for a typical microelectronic device because of the need to simultaneously protect the device from the environment while allowing interaction with it. The goal of this work is to create an underwater acoustic sensor package that will allow sound transmission to the sensor while keeping out moisture and salt ions. A bio-inspired package, based on the hearing mechanisms in fish and other aquatic animals, has been developed for this purpose. The package will ensure reliability in the underwater environment while not interfering with the transmission of sound. The sensor design incorporates magnetostrictive iron-gallium (Galfenol) nanowires. Arrays of cilia-like nanowires mechanically respond to incoming sound waves, thus creating magnetic fields that are sensed by a GMR sensor. The package is designed to contain the nanowires in a fluid medium, leaving them free to move. Materials matching the acoustic impedance of seawater are incorporated to allow sound to penetrate the package. Acoustic properties of various materials were investigated using scanning acoustic microscopy for this application. A fabrication process for the package is presented. The fabrication incorporates a room temperature soldering process that will not harm the sensor during the bonding of package components.
The development of integrated isolators is critical to the functional integration of optics within OEM devices and systems. Bulk isolators have proven to be the most important components in many fiber optic systems due to their ability to protect light sources from back-reflected light. Such reflections are created at each component interface, inhomogeneity, or other perturbation in the path of the light. This paper reviews the operation of and current work in integrated isolators. Several methods for fabricating monolithically integrated magneto-optical isolators are discussed, including the fabrication of garnets, magnets, and cladding/buffer layers. Garnets are traditionally grown by liquid phase epitaxy (LPE) at temperatures and environments that are not friendly to semiconductors or other common substrates. More importantly, LPE requires epitaxial growth, which dictates garnet substrates and therefore hybrid integration techniques. We have used metallorganic chemical vapor deposition (MOCVD), sputtering, and metallorganic chemical liquid deposition (MOCLD) to deposit single-phase yttrium iron garnet (YIG). A variety of substrates were used, including MgO and SiO2 which are promising buffer layer materials. The chemical, structural, and optical properties of the resulting films are discussed. We have also used a variety of sputtering techniques to integrate permanent magnet films with semiconductor processing. These magnets are sufficient for biasing the magneto-optical element. The chemical, structural and magnetic properties of these materials, as well as total integration will be discussed.
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