M.R. Madani

Characterization of silicon oxide films grown at room temperature by point-to-plane corona discharge

Oxide films grown on silicon in dry oxygen ambient at room temperature by negative point-to-plane corona discharge are investigated. A significant oxidation rate is observed at room temperature using this technique. Electrical properties of these room termperature grown oxides are examined. The capacitance-voltage measurements on the MOS structures fabricated from these oxides indicate a negative flat-band voltage of −1.5 V. Interface state density distribution in the range of 1010−1013 cm−2(eV)−1 is observed with a value of 2×1010 cm−2(eV)−1 at 0.17 eV above the valence band edge. Electrical conduction through the oxide is greater for negative values of applied gate bias voltages and the magnitude of conduction through the oxide decreases with decreasing current density during the corona discharge. Oxides grown at room temperature by this technique may find selective application in low temperature device processing.

Current density distribution measurement of negative point-to-plane corona discharge

The current density distribution on the plate electrode of a point-to-plane corona discharge is measured with a computer-controlled measuring system. The measurements are taken by rotating the plate which consist of built-in arrays of orthogonal probes. The current-density distribution can be measured for different separation distances between the point electrode and the plane electrode while the applied high voltage can be varied from the voltage required for the onset of corona discharge to 30 kV. The current-density distribution of a single needle is symmetric around its center point within the accuracy of the measurement system. However, the current-density distribution is radially nonuniform. The computer-controlled measuring system is capable of measuring the current distribution of single point and multipoint electrodes.

A Reliable and Cost-Effective Sand Monitoring System on the Field Programmable Gate Array (FPGA)

Sand monitoring gives the benefits of avoiding equipment erosion and production failure in the oil industry. This paper presents the design and implementation of a reliable and cost-effective sand monitoring system for measuring sand production in gas and oil flows in real time. The designed monitoring system involves two acoustic emission (AE) sensors and one Doppler sensor for gauging the sand impaction and the velocity of sand particles in a nonintrusive manner, respectively. It is implemented on a field programmable gate array (FPGA) as a prototype for real-time data acquisition and processing, and evaluated using a testbed pump skid available in our laboratory. Relying on a low-cost FPGA board to integrate all acquisition and processing functionality, our monitoring system can measure the sand production amount on-the-fly reliably with high accuracy, according to our experimental evaluation. It is likely to achieve better accuracy than one without the Doppler sensor. The proposed monitoring system is affordable for wide deployment, given its high accuracy, good resilience to surrounding noise, and low cost (when compared with commercially available systems whose price tags can be some tenfold higher).

Electrical properties of the oxide grown on Si at room temperature using point to plane corona discharge

The electrical properties of SiO/sub 2/ grown at 25 degrees C in dry oxygen ambient with a point-to-plane corona discharge are examined. A flat-band voltage of about -2.5 V is obtained from the C-V characteristic curves of the oxides grown with an average corona discharge current density of -30 mu A/cm/sup 2/. The flat-band voltage shift is related to the corona discharge current density. The oxides grown by this method with this relatively high current density values are found to have instability due to both ion motion and charge injection in the oxide. The charge transport through this oxide at high positive gate voltage values shows behavior similar to the Frenkel-Pool mechanism.<<ETX>>

Microhotplates for low power, and ultra dense gaseous sensor arrays using recessed silica aerogel for heat insulation

In the operation of air pitted gaseous sensor the microhotplate (μHP) consumes almost all the power used by the sensor. The required area to micromachine the air pit for the μHP of a single sensor is several times more than the actual area required by the sensor itself. The feasibility of implementing low power and ultra dense gaseous sensor array is investigated by developing a new μHP structure using recessed silica aerogel. In comparison with the conventional μHP structure, the recessed aerogel not only has decreased the utilized area of the chip almost ten folds (181 × 181 μm2 vs. 573 × 573 μm2) to maintain a temperature of 360 °C but also has decreased the power consumed by each μHP more than two folds (1 mW vs. 2:1 mW). As the number of sensors increases in a sensor array, the saved area of the chip increases quadratic by using the new structure. Moreover, the power consumed by the new designed structure reduces drastically.

Interface properties of the oxide grown on Si at low temperatures using point to plane corona discharge

The interface trap density of oxide film grown on silicon at low temperatures using point to plane corona discharge is studied. For oxide grown with this method with a 1-cm electrode distance, an interface density on the order of 10/sup 13/ to 10/sup 14/ eV/sup -1/ cm/sup -2/ is obtained from the high-frequency current-voltage curves. This is higher than the interface trap density of the oxide grown by the conventional high-temperature oxidation method. The interface trap density can be lowered by changing such processing parameters as the distance between the electrodes and the corona discharge current density.<<ETX>>

Design and COMSOL simulation of koch snowflake dipole fractal antennas

This paper highlights the design and simulation of Koch snowflake half-wave dipole antennas for RFID (radio frequency identification) use. The fractal antennas are designed to be compact as well as multi-band use at UHF (ultra high frequency) and microwave frequencies. The first three iterations of the Koch snowflake were designed and simulated through COMSOL. Each antenna was designed for the UHF band and an analysis of the second band is given in the paper. Each antenna was simulated as a copper wires with varying, decreasing widths and 1 mm thickness. The reduction of the physical length and the multi-band capabilities of the fractal antennas are presented. The antennas physical length decreases while the height increases after every iteration and has a return loss of at least 10 dB. Every antenna will be more compact by using less physical length than its previous iteration. Also, in order to model an antenna that has resonance at 860–960 MHz and 2.4–2.48 GHz, common RFID ranges, the inclusion of a substrate with the fractal antennas are presented in this paper.

COMSOL simulations of DCSRR with band-pass and band-stop characteristics

In this paper, a demonstration of a standard pair of complementary split ring resonators (CSRR) can be enhanced by the addition of another pair of rings. These additional pairs allow for greater enhancement of the standard CSRRs ability to mitigate unwanted frequencies, and enhance desired frequencies. Various ring orientations and geometries are crafted and simulated in COMSOL. At 2.4 GHz, the band-pass CSRR achieved a return loss of 44.015 dB while the band-stop achieved a S21 measurement of −56.8 dB. In addition, the band-pass CSRR shows the attenuation of frequencies that surround the 2.4 GHz frequency. The presented results show possible enhancement or blocking of frequencies used for S-band RFID applications.

MOX gas sensors using multilayer aerogel

In this work for the first time we have demonstrated the feasibility of multilayer silica aerogel interleaved with thin layers of SiO2, to replace the micromachined air pit used in fabrication of metal oxide (MOX) gas sensors. Microhotplate is the most important structure of MOX gas sensors since it provides the desired uniform temperatures ranging from 200 oC to 500 oC for the sensing material. Based on our previous work, in order to achieve this operating temperature we must have a thick layer of 5 to 20 μm aerogel. However, in the literature we cannot find reports that indicate multilayer spin-coated aerogel is possible. In our laboratory we have successfully spin coated two layers of aerogel with high porosity of 85% and low refractive index of 1.05. We have investigated the formation of thicker multilayer aerogel by having sputtered SiO2 as interlayer. The heat insulation capability of multilayer is reported in both steady state and transient mode.

Application of Nicollian-Reisman model to negative point-to-plane corona oxidation of silicon

The Nicollian-Reisman oxidation model based on viscous flow principles is used to curve fit data obtained for the corona discharge oxidation of silicon. The application of this model to corona discharge oxidation of silicon in dry oxygen ambient indicates that the silicon oxidation process at a given temperature is more reaction-rate-controlled in corona discharge than the conventional thermal oxidation of silicon. The enhancement in the rate of oxidation with corona discharge is attributed in part to an increase in surface relaxation during oxidation.<<ETX>>