A fringing field capacitive sensor is described for measuring the moisture content (MC) and temperature of agricultural commodities. Sensor performance was characterized by mounting the device on handheld probes and in acrylic canisters to determine the dielectric constant and MC of wheat and corn. The handheld probes demonstrated a promising capability to measure the MC of grain in hoppers, truck beds, and cargo holds. It is proposed that the sensors be supported on cables in grain silos and storage bins to acquire in situ data for grain storage management and control of aeration systems. The sensor is watertight and constructed with corrosion resistant materials which allow MC measurements to be made of industrial materials, chemicals, and fuels.

The Growth of ultrathin oxides in N2O ambient has been a subject of extensive research for submicron CMOS technology. Oxides grown in N2O tend to have a higher charge-to-breakdown, less charge trapping under constant current stress, and less interface state generation under current stress and radiation than conventional oxides grown in oxygen [1,2]. In addition the penetration of boron through N2O oxides is significantly less than through conventional thermal oxides [3]. The improved characteristics of N2O are due to an interfacial pileup of nitrogen atoms [1-3]. Thus the growth of thermal oxides in N2O provides a method for obtaining many of the more favorable aspects of reoxidized-nitrided silicon dioxides, with a much simpler process.

Recent work in electron cyclotron resonance chemical vapor deposition (ECR-CVD) SiC coating technology has demonstrated the potential for fabricating high-quality SiC membranes for x-ray lithography masks. Stoichiometric SiC coatings were deposited on 100-mm-diam silicon wafers at a susceptor temperature of 930 °C in a single-wafer ECR-CVD system at deposition rates of 200 Å/min with better than ±5% thickness uniformity and ±1% wafer-to-wafer reproducibility. The coatings were deposited under tensile stress, with a wafer-to-wafer stress repeatability of ±15%. The coatings were extremely smooth, and x-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that they were amorphous with scattered submicron crystalline inclusions. One- and 2-μm-thick membranes were made in 30 and 50 mm diameters at yields of 80%. A peak transmittance of 65% was measured at 633 nm for 1-μm-thick SiC membranes. The bi-axial elastic modulus, E/(1−ν), of the SiC membranes was (4–6)×1012 dyn/cm2, about three times greater than that of (100) Si membranes. Hydrogen was undetectable in the form of either CH or SiH bonds to within the experimental detection limit of <10 ppm. Out-of-plane distortion could not be detected after an absorbed dose of 9.6 or 29 MJ/cm3 during exposure at the Center for X-ray Lithography beamline at the University of Wisconsin’s Aladdin synchrotron. The membrane transmittance decreased by about 1% after the 29 MJ/cm3 dose. Plans for future work include modifications to the ECR-CVD equipment to increase substrate temperature uniformity, temperature limit, and deposition rate, and to reduce defect density.

The design, performance, and potential applications are described for capacitive transducers with curved electrodes. A curved electrode governs the deflection of a compliant electrode under applied stress. A dielectric film on one electrode provides a variable region of fixed electrode spacing. The sensitivity and linear dynamic range of the transducers are higher and wider than devices with parallel electrodes. An electrical advantage is obtained from the permittivity of the dielectric film and a mechanical advantage from its thinness. Transducers have been constructed with silicon diaphragms that bend and polymer membranes that stretch in response to uniform pressure. The silicon sensors measured dynamic pressure changes over a linear range of 125 dB. An 885% change in capacitance was obtained for a sensor with a thin silicon diaphragm. Sensors with polycarbonate membranes demonstrated the ability of a low-cost transducer to measure pressure, fluid flow, displacement, and tilt. An active capacitive bridge circuit was developed to linearly measure capacitance changes up to 1000% and to control electrostatic actuators by force-balanced feedback. Methods and materials to construct microscale transducers are discussed along with the performance limitations of electrostatic actuation.Index Terms-Capacitive transducer, curved electrode, electret transducer, electrostatic actuator, force-balanced feedback, nullbalanced bridge (NBB), ultrasound transducer.