Low Voltage Nanoelectromechanical Switches Based on Silicon Carbide Nanowires

We report experimental demonstrations of electrostatically actuated, contact-mode nanoelectromechanical switches based on very thin silicon carbide (SiC) nanowires (NWs). These NWs are lithographically patterned from a 50 nm thick SiC layer heteroepitaxially grown on single-crystal silicon (Si). Several generic designs of in-plane electrostatic SiC NW switches have been realized, with NW widths as small as ~20 nm and lateral switching gaps as narrow as ~10 nm. Very low switch-on voltages are obtained, from a few volts down to ~1 V level. Two-terminal, contact-mode “hot” switching with high on/off ratios (>10^2 or 10^3) has been demonstrated repeatedly for many devices. We find enhanced switching performance in bare SiC NWs, with lifetimes exceeding those based on metallized SiC NWs

Monocrystalline silicon carbide nanoelectromechanical systems

SiC is an extremely promising material for nanoelectromechanical systems given its large Young's modulus and robust surface properties. We have patterned nanometer scale electromechanical resonators from single-crystal 3C-SiC layers grown epitaxially upon Si substrates. A surface nanomachining process is described that involves electron beam lithography followed by dry anisotropic and selective electron cyclotron resonance plasma etching steps. Measurements on a representative family of the resulting devices demonstrate that, for a given geometry, nanometer-scale SiC resonators are capable of yielding substantially higher frequencies than GaAs and Si resonators

Experimental Performance of a Micromachined Heat Flux Sensor

Steady-state and frequency response calibration of a microfabricated heat-flux sensor have been completed. This sensor is batch fabricated using standard, micromachining techniques, allowing both miniaturization and the ability to create arrays of sensors and their corresponding interconnects. Both high-frequency and spatial response is desired, so the sensors are both thin and of small cross-sectional area. Thin-film, temperature-sensitive resistors are used as the active gauge elements. Two sensor configurations are investigated: (1) a Wheatstone-bridge using four resistors; and (2) a simple, two-resistor design. In each design, one resistor (or pair) is covered by a thin layer (5000 A) thermal barrier; the other resistor (or pair) is covered by a thick (5 microns) thermal barrier. The active area of a single resistor is 360 microns by 360 microns; the total gauge area is 1.5 mm square. The resistors are made of 2000 A-thick metal; and the entire gauge is fabricated on a 25 microns-thick flexible, polyimide substrate. Heat flux through the surface changes the temperature of the resistors and produces a corresponding change in resistance. Sensors were calibrated using two radiation heat sources: (1) a furnace for steady-state, and (2) a light and chopper for frequency response

Quality factor issues in silicon carbide nanomechanical resonators

Nanomechanical resonators with fundamental mode resonance frequencies in the Very-High Frequency (VHF), Ultra-High Frequency (UHF) range and microwave L-band are fabricated from monocrystalline silicon carbide thin film material, and measured by magnetomotive transduction, combined with a balanced bridge read out circuit. For resonators made from the same film, we measured the frequency (i.e., geometry) dependence of the quality factor. It is found that the quality factor of these resonators decreases when the frequency increases. This indicates the importance of clamping loss in this regime. In addition, from studies of resonators made from different chips with varying surface roughness, we found a strong correlation between surface roughness of the silicon carbide thin film material and the quality factor of the resonators made from it. Understanding the dissipation mechanisms, and thus improving the quality factor of these resonators, is important for implementing applications promised by these devices

Personal Navigation via High-Resolution Gait-Corrected Inertial Measurement Units

In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zerovelocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks

Personal Navigation via High-Resolution Gait-Corrected Inertial Measurement Units

In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zerovelocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks

Personal navigation via high-resolution gait-corrected inertial measurement units

In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zero-velocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks. © 2010 IEEE

Design and fabrication of a micromachined electrostatically suspended gyroscope

The current paper describes the design and fabrication of a micromachined electrostatically suspended gyroscope. Electrostatic levitation is employed to suspend the rotor, eliminating the mechanical bearing and thus friction effects between the rotor and the substrate, hence improving long-term stability. The rate of rotation can be measured by detecting the torque-induced displacement of the spinning rotor using capacitive interface circuits. The device structure and its basic operating principle are described, as well as theoretical background and design considerations. The fabrication process of the gyroscope relies on glass/silicon/glass stack bonding and deep dry etching and is outlined in detail. Initial prototypes realized with this fabrication process are presented and described