6 research outputs found
Microfabricated Ice-Detection Sensor
Knowledge of ice conditions on important aircraft lift and control surfaces is critical for safe operation. These conditions can be determined with conventional ice-detection sensors, but these sensors are often expensive, require elaborate installation procedures, and interrupt the airflow. A micromachined, silicon-based, flush-mounted sensor which generates no internal heat has been designed, batch fabricated, packaged, and tested. The sensor is capable of distinguishing between an ice-covered and a clean surface. It employs a bulk micromachined wafer with a 7 micrometer-thick, boron-doped, silicon diaphragm which serves as one plate of a parallel-plate capacitor. This is bonded to a second silicon wafer which contains the fixed electrodes, one to drive the diaphragm by application of a voltage, the other to measure the deflection by a change in capacitance. The diaphragm sizes ranged from 1x1 mm to 3x3 mm, and the gap between parallel-plate capacitors is 2 micrometers. A 200 V d.c. was applied to the driving electrode which caused the capacitance to increase approximately 0.6pf, from a nominal capacitance of 0.6pf, when the surface was ice free. After the sensor was cooled below the freezing point of water, the same voltage range was applied to the drive electrode. The capacitance increased by the same amount. Then a drop of water was placed over the diaphragm and allowed to freeze. This created an approximately 2mm-thick ice layer. The applied 200V d.c. produced no change in capacitance, confirming that the diaphragm was locked to the ice layer. Since the sensor uses capacitive actuation, it uses very little power and is an ideal candidate for inclusion in a wireless sensing system
Review of Graphene Technology and Its Applications for Electronic Devices
Graphene has amazing abilities due to its unique band structure characteristics defining its enhanced electrical capabilities for a material with the highest characteristic mobility known to exist at room temperature. The high mobility of graphene occurs due to electron delocalization and weak electronâphonon interaction, making graphene an ideal material for electrical applications requiring high mobility and fast response times. In this review, we cover grapheneâs integration into infrared (IR) devices, electro-optic (EO) devices, and field effect transistors (FETs) for radio frequency (RF) applications. The benefits of utilizing graphene for each case are discussed, along with examples showing the current state-of-the-art solutions for these applications
Rapid Identification of Stacking Orientation in Isotopically Labeled Chemical-Vapor Grown Bilayer Graphene by Raman Spectroscopy
The growth of large-area bilayer
graphene has been of technological
importance for graphene electronics. The successful application of
graphene bilayers critically relies on the precise control of the
stacking orientation, which determines both electronic and vibrational
properties of the bilayer system. Toward this goal, an effective characterization
method is critically needed to allow researchers to easily distinguish
the bilayer stacking orientation (i.e., AB stacked or turbostratic).
In this work, we developed such a method to provide facile identification
of the stacking orientation by isotope labeling. Raman spectroscopy
of these isotopically labeled bilayer samples shows a clear signature
associated with AB stacking between layers, enabling rapid differentiation
between turbostratic and AB-stacked bilayer regions. Using this method,
we were able to characterize the stacking orientation in bilayer graphene
grown through Low Pressure Chemical Vapor Deposition (LPCVD) with
enclosed Cu foils, achieving almost 70% AB-stacked bilayer graphene.
Furthermore, by combining surface sensitive fluorination with such
hybrid <sup>12</sup>C/<sup>13</sup>C bilayer samples, we are able
to identify that the second layer grows underneath the first-grown
layer, which is similar to a recently reported observation