Capacitance probe

Abstract: There is a continued need for better methods to perform accurate, real-time, nearly continuous soil water measurements at specific depth intervals, with minimal soil disturbance, and covering field-scale areas. The objectives of this research were to assess the characteristics of a newly developed multisensor capacitance probe and to calibrate the sensors against a Mattapex silt loam (fine-silty, mixed, mesic Aquic Hapludult) soil. The soil was uniformly packed in small increments, with the aid of a large hydraulic press, in a wooden box (35.5 by 35.5 cm, 40.5 cm deep). Probe installation in the boxed soil mimicked that required for correct field installation. A highly significant (r2 = 0.992 for n = 15, and RMSE = 0.009 cm 3 cm -3 water), nonlinear (θ r = 0.490 SF 2.1674 ) relationship was found between the soil volumetric water content (0 v , cm 3 cm -3 ) and the scaled frequency |SF = (F a - F s )(F a -F w ) -1 ]. The SF represents the ratio of individual sensor's frequency (inside PVC pipe) response in soil (F,) compared with sensor responses in air (F,) and in nonsaline water (F w ) at room temperature ( 22°C). Axial and radial sensitivity studies showed that these capacitance sensors give integrated readings over a primary depth interval of 10 cm and a radial capacitance fringe within 10 cm of the wall of the access pipe. Temperature effects of air and water were measured, and the calculated effects on assessment of θ ν were less than the RMSE for a temperature range of 10 to 30°C. Our calibration studies indicate that these multisensor capacitance probes can be used to accurately measure volumetric soil water contents in a soil water monitoring system.

Abstract: Method and structures are provided for conformal capacitor dielectrics over textured silicon electrodes for integrated memory cells. Capacitor structures and first electrodes or plates are formed above or within semiconductor substrates. The first electrodes include hemispherical grain (HSG) silicon for increasing the capacitor plate surface area. The HSG topography is then exposed to alternating chemistries to form monolayers of a desired dielectric material. Exemplary process flows include alternately pulsed metal organic and oxygen source gases injected into a constant carrier flow. Self-terminated metal layers are thus reacted with oxygen. Near perfect step coverage allows minimal thickness for a capacitor dielectric, given leakage concerns for particular materials, thereby maximizing the capacitance for the memory cell and increasing cell reliability for a given memory cell design. Alternately pulsed chemistries are also provided for depositing top electrode materials with continuous coverage of capacitor dielectric, realizing the full capacitance benefits of the underlying textured morphology.

Abstract: As an emerging technology in the area of energy storage, the double-layer capacitor is a promising device for certain niche applications. The double-layer capacitor is a low voltage device exhibiting an extremely high capacitance value in comparison with other capacitor technologies of a similar physical size. Capacitors with values in excess of 1500 F are now available. In slow discharge applications on the order of a few seconds, the classical equivalent circuit for a double-layer capacitor, composed of a capacitance (C), an equivalent parallel resistance (EPR), and an equivalent series resistance (ESR), can adequately describe capacitor performance. The focus of this work is the determination of these parameters for four different capacitors from discharge data using standard laboratory equipment such as an oscilloscope. Capacitance values are calculated using a change in stored energy approach which allows determination of an initial capacitance, a discharge capacitance, and variations in capacitance with voltage. The sensitivity of ESR and capacitance to charge rate and initial charge voltage is also reported.

Abstract: Variations in topography and material properties of the surface layer of a body are observed in microscopic imaging using a scanning capacitance probe. The acronym SCaM identifying the process and apparatus is derived from the phrase scanning capacitance microscope. The material properties observable by SCaM are the surface-electric property representative of the complex dielectric constant of the surface material and the surface-mechanical property representative of the elastic constant of the surface material.