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The NASA Glenn Research Center is constructing a 616 element scanning phased array antenna using thin film BaxSr1-xTiO3 based phase shifters. A critical milestone is the production of 616 identical phase shifters at 19 GHz with ≈4 dB insertion loss and at least 337.5° phase shift with 3 percent bandwidth. It is well known that there is a direct relationship between dielectric tuning and loss due to the Kramers-Kronig relationship and that film crystallinity and strain, affected by the substrate template, play an important role. Ba0.50Sr0.50TiO3 films, nominally 400 nm thick, were deposited on 48 0.25 mm thick, 5 cm diameter LaAlO3 wafers. Although previous results suggested that Mn-doped films on MgO were intrinsically superior in terms of phase shift per unit loss, for this application phase shift per unit length was more important. The composition was selected as a compromise between tuning and loss for room temperature operation (e.g. crystallinity progressively degrades for Ba concentrations in excess of 30 percent). As a prelude to fabricating the array, it was necessary to process, screen, and inventory a large number of samples. Variable angle ellipsometry was used to characterize refractive index and film thickness across each wafer. Microstructural properties of the thin films were characterized using high resolution X-ray diffractometry. Finally, prototype phase shifters and resonators were patterned on each wafer and RF probed to measure tuning as a function of dc bias voltage as well as peak (0 field) permittivity and unloaded Q. The relationship among film quality and uniformity and performance is analyzed. This work presents the first statistically relevant study of film quality and microwave performance and represents a milestone towards commercialization of thin ferroelectric films for microwave applications.

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This paper reviewed work to date on multicomponent oxides deposited, utilizing openatmosphere Combustion Chemical Vapor Deposition for electronic applications. Epitaxial barium strontium titanate and strontium titanate thin films were deposited on (100) MgO single crystal substrates. They were patterned to form interdigitated structures for electrically tunable devices, namely, coupled microstripline phase shifters (CMPS). The undoped, as-deposited perovskite dielectrics exhibited a figure of merit of 53°/dB at 20 GHz and 23°C, indicating high degree of tunability and fairly low loss. High-permittivity (ε=263), polycrystalline BST and SrTiO3 were studied for dynamic random access memory, and leakage current density of 10−7 A/cm2 was measured. Intended for non-volatile ferroelectric memory, lead zirconium titanate was deposited onto a seed layer of perovskite structure to prevent the growth of the unwanted pyrochlore phase. To function as buffer layers for superconductor applications, epitaxial CeO2, YSZ, SrTiO3, LaAlO3, Y2O3, and Yb2O3 coatings on single crystal and textured nickel substrate were investigated. Electronic analyses and characterization, using SEM, EDS, XRD, and X-ray pole figures, were presented.