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Fluidized-bed chamber in which particles in bed are capacitively heated produces high yields of polycrystalline silicon for semiconductor devices. Deposition of unrecoverable silicon on chamber wall is reduced, and amount of recoverable silicon depositing on seed particles in bed is increased. Particles also have a size and density suitable for direct handling without consolidation, unlike silicon dust produced in heated-wall chambers.
It is shown that pulsed electric fields can be produced over extended volumes by taking advantage of the internal capacitances in a stacked array of electrodes. The design, construction, and performance of practical arrays are discussed. The prototype arrays involved fields of 100-1000 V/cm extending over several centimeters. Scaling to larger physical dimensions is straightforward.
The derivation of a simple expression for the capacitance C(V) associated with the transition region of a p-n junction under a forward bias is derived by phenomenological reasoning. The treatment of C(V) is based on the conventional Shockley equations, and simpler expressions for C(V) result that are in general accord with the previous analytical and numerical results. C(V) consists of two components resulting from changes in majority carrier concentration and from free hole and electron accumulation in the space-charge region. The space-charge region is conceived as the intrinsic region of an n-i-p structure for a space-charge region markedly wider than the extrinsic Debye lengths at its edges. This region is excited in the sense that the forward bias creates hole and electron densities orders of magnitude larger than those in equilibrium. The recent Shirts-Gordon (1979) modeling of the space-charge region using a dielectric response function is contrasted with the more conventional Schottky-Shockley modeling.
Rugged capacitive transducer measures thickness of film of liquid flowing over wind-tunnel model or other object. Transducer mounted flush with surface of model to preserve model outline, thus minimally disturbing wind-tunnel and film flows. Additional uses include thickness control of paint or nonmetallic solid films.
The frequency-modulated (FM) oscillator described is part of a blade tip clearance measurement system that meets the needs of a wide class of fans, compressors, and turbines. As a result of advancements in the technology of ultra-high-frequency operational amplifiers, the FM oscillator requires only a single low-cost integrated circuit. Its carrier frequency is 42.8 MHz when it is used with an integrated probe and connecting cable assembly consisting of a 0.81 cm diameter engine-mounted capacitance probe and a 61 cm long hermetically sealed coaxial cable. A complete circuit analysis is given, including amplifier negative resistance characteristics. An error analysis of environmentally induced effects is also derived, and an error-correcting technique is proposed. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a rotor blade thickness of 1.2 mm. High-temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum permissible seal temperature. The major source of error is the residual FM oscillator noise, which produces a clearance error of + or - 10 microns at a clearance of 0.5 mm. The oscillator electronics accommodates the high rotor speeds associated with small engines, the signals from which may have frequency components as high as 1 MHz.
A measurement technique has been developed which allows noncontact capacitance-voltage measurements to be made using a gate electrode located remote from the semiconductor surface under study. With gate electrodes about 0.5 mm in diameter and gate to semiconductor separations of about 1500 A, it was possible to generate data entirely comparable to that obtained with integrated MIS structures but with the advantage that there was access directly to the free-semiconductor surface. This technique was applied to bulk single-crystal Si and InP samples.
Simple displacement-measuring circuit senses capacitance between two parallel conducting plates and produces output signal, with frequency proportional to distance between plates. Principle of circuit provides advantages over other methods because of frequency-encoded output and high linearity. Used to measure displacements.
Silicon dioxide films grown under dry and wet oxidation environment on beta-SiC films have been studied. The beta-SiC films had been heteroepitaxially grown on both on-axis and 2-deg off-axis (001) Si substrates. Capacitance-voltage and conductance-voltage characteristics of metal-oxide-semiconductor structures were measured in a frequency range of 10 kHz to 1 MHz. From these measurements, the interface trap density and the effective fixed oxide charge density were observed to be generally lower for off-axis samples.
Improved capacitive sensor used to detect presence and/or measure thickness of layer of liquid. Electrical impedance or admittance of sensor measured at prescribed frequency, and thickness of liquid inferred from predetermined theoretical or experimental relationship between impedance and thickness. Sensor is basically a three-terminal device. Features interdigitated driving and sensing electrodes and peripheral coplanar ground electrode that reduces parasitic effects. Patent-pending because first to utilize ground plane as "shunting" electrode. System less expensive than infrared, microwave, or refractive-index systems. Sensor successfully evaluated in commercial production plants to characterize emulsions, slurries, and solutions.
The S-parameters of several different quantum well double barrier diodes have been measured. A technique has been developed for measuring whisker contacted diodes with an HP 8510B automatic network analyzer. Special coaxial mounts using K-connectors were designed to enable measurements up to 20 GHz. The voltage-dependent conductance and capacitance were derived from the measured reflection coefficient of each device. The C/V characteristics were observed to exhibit an anomalous increase at voltages corresponding to the negative differential resistance region (NDR). These are the first reported S-parameter measurements in the negative differential resistance region of quantum well double barrier diodes. A theory is presented that explains, in part, the observed results.
Crosstalk eliminated by maintaining voltages on all electrodes at same amplitude, phase, and frequency. Each output feedback-derived control voltage, change of which indicates proximity-induced change in capacitance of associated sensing electrode. Sensors placed close together, enabling imaging of sort. Images and/or output voltages used to guide robots in proximity to various objects.
Improved capacitive proximity sensors constructed by incorporating one or more additional driven shield(s). Sensitivity and range of sensor altered by adjusting driving signal(s) applied to shield(s). Includes sensing electrode and driven isolating shield that correspond to sensing electrode and driven shield.
A phase discriminating capacitive sensor array system which provides multiple sensor elements which are maintained at a phase and amplitude based on a frequency reference provided by a single frequency stabilized oscillator. Sensor signals provided by the multiple sensor elements are controlled by multiple phase control units, which correspond to the multiple sensor elements, to adjust the sensor signals from the multiple sensor elements based on the frequency reference. The adjustment made to the sensor signals is indicated by output signals which indicate the proximity of the object. The output signals may also indicate the closing speed of the object based on the rate of change of the adjustment made, and the edges of the object based on a sudden decrease in the adjustment made.
Like other capaciflectors described in prior articles in NASA Tech Briefs, this one includes sensing electrode driven by alternating voltage, giving rise to electric field in vicinity of electrode; object entering electric field detected by its effect on capacitance between sensing electrode and electrical ground. Also includes shielding electrode (in this case, driven shield 1), excited via voltage follower at same voltage as that applied to sensing electrode to concentrate more of electric field outward from sensing electrode, increasing sensitivity and range of sensor. Because shielding electrode driven via voltage follower, it does not present significant electrical load to source of alternating voltage.
Improved class of compact, high-resolution capacitive displacement sensors operates at excitation frequency of 915 MHz and measures about 7.5 by 4 by 2 centimeters. Contains commercially available 915-MHz oscillator and transmission-line resonator. Resonator contains stripline inductor in addition to variable capacitor. Ultrahigh excitation frequency offers advantages of resolution and frequency response. Not deleteriously affected by mechanical overdriving, or contact between electrodes.
Multiple capacitive sensors and active targets used to measure distance between, and relative orientation of, two objects. Sensed target signals processed and used by control systems to align objects to be joined. Shapes, sizes, and layouts of sensors and targets optimized for specific application. Particular layout of targets and sensors enables determination of relative position and orientation of two objects in all six degrees of freedom.
Steerable capacitive proximity sensor of "capaciflector" type based partly on sensing units described in GSC-13377 and GSC-13475. Position of maximum sensitivity adjusted without moving sensor. Voltage of each driven shield adjusted separately to concentrate sensing electric field more toward one side or other.
A capacitor having two substantially parallel conductive faces is acoustically coupled to a conductive sample end such that the sample face is one end of the capacitor. A non-contacting dielectric may serve as a spacer between the two conductive plates. The formed capacitor is connected to an LC oscillator circuit such as a Hartley oscillator circuit producing an output frequency which is a function of the capacitor spacing. This capacitance oscillates as the sample end coating is oscillated by an acoustic wave generated in the sample by a transmitting transducer. The electrical output can serve as an absolute indicator of acoustic wave displacement.