We apply a systematic approach to identify a highk/metal gate stack degradation mechanism. Our results demonstrate that the SiO 2 interfacial layer controls the overall degradation and breakdown of the high-k gate stacks stressed in inversion. Defects contributing to the gate stack degradation are associated with the high-k/metal-induced oxygen vacancies in the interfacial layer.

A low profile dual polarized bowtie antenna element is studied for an S-band (3 GHz) wide-scan application in a large-scale (nearly an infinitely large) uniformly excited phased array. The study shows that the array with such elements, when connected, is capable of scanning up to ±75 • at E-plane and ±15 • at H-plane for horizontal and vertical polarizations respectively. The bandwidth of the infinite array with such elements across these scan angles is 10% and 25% for the active reflection coefficient of −10 dB and −5 dB respectively.

A low-profile and wide-scan phased-array antenna of connected cross-bowtie elements is proposed. The design goals and considerations are based on the applications requiring the integration of a large array antenna with composite sandwich structures, such as antennas on aircraft. In a very large array environment (modelled approximately as an infinite array), the main beam of the proposed antenna can be steered up to ±75°at azimuth and ±15°at elevation over bandwidths of 10% and 25% with active reflection coefficients below −10 dB and −5 dB, respectively. A Monte Carlo analysis of critical manufacturing and alignment tolerances shows the desired performance is achieved with the cumulative distribution probability over 80% under the uniformly distributed random combinations of the tolerances. Experimental results of a 7×7 element array prototype agree well with the simulations of this small-scale array case. The experiments show that this small-scale prototype is capable of steering the beam within the range of [−60°, 60°] at azimuth and [−15°, 15°] at elevation with the predicted performance satisfying the targeted application requirements and mechanical constraints. The achieved combination of the wide beam steering performance, relatively low antenna profile, and suitability of its feeding structure for sandwiched electro-mechanical integration makes this design unique with respect to the previously published results.INDEX TERMS Bowtie antenna, composite sandwich structure, connected array, fuselage integration, phased array.

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Edge truncation effects are critical when designing a phased array, as these can lead to the variation of the active antenna impedance and radiation pattern between individual array elements. This paper investigates edge truncation effects in an array of connected Bowtie antenna elements that has been initially designed through an infinite array approach. This design represents a novel implementation of the connected-array concept that offers a wide-scan performance with up to ± 80 • scan range in the E-plane (in the infinite array). The goal of this study is to estimate the minimum size of a realistic finite array of such connected Bowtie antennas.