273 research outputs found
Measuring Charge Transport in an Amorphous Semiconductor Using Charge Sensing
We measure charge transport in hydrogenated amorphous silicon (a-Si:H) using
a nanometer scale silicon MOSFET as a charge sensor. This charge detection
technique makes possible the measurement of extremely large resistances. At
high temperatures, where the a-Si:H resistance is not too large, the charge
detection measurement agrees with a direct measurement of current. The device
geometry allows us to probe both the field effect and dispersive transport in
the a-Si:H using charge sensing and to extract the density of states near the
Fermi energy.Comment: 4 pages, 4 figure
Measurement of the Casimir force between dissimilar metals
The first precise measurement of the Casimir force between dissimilar metals
is reported. The attractive force, between a Cu layer evaporated on a
microelectromechanical torsional oscillator, and an Au layer deposited on an
AlO sphere, was measured dynamically with a noise level of 6
fN/. Measurements were performed for separations in the 0.2-2
m range. The results agree to better than 1% in the 0.2-0.5 m range
with a theoretical model that takes into account the finite conductivity and
roughness of the two metals. The observed discrepancies, which are much larger
than the experimental precision, can be attributed to a lack of a complete
characterization of the optical properties of the specific samples used in the
experiment.Comment: 6 pages, 4 figure
Diagnostics: Indicators and Transparency in the Anti-Corruption Industry
Discussion of transparency and indexes of corruption and their effect on the growing anti-corruption movement. Trust in numbers may lead to opacity rather than transparenc
Fabrication and characterisation of nanocrystalline graphite MEMS resonators using a geometric design to control buckling
The simulation, fabrication and characterisation of nanographite MEMS resonators is reported in this paper. The deposition of nanographite is achieved using plasma-enhanced chemical vapour deposition directly onto numerous substrates such as commercial silicon wafers. As a result, many of the reliability issues of devices based on transferred graphene are avoided. The fabrication of the resonators is presented along with a simple undercutting method to overcome buckling, by changing the effective stress of the structure from 436 MPa compressive, to 13 MPa tensile. The characterisation of the resonators using electrostatic actuation and laser Doppler vibrometry is reported, demonstrating resonator frequencies from 5–640 kHz and quality factor above 1819 in vacuum obtained
Modeling Single Electron Transfer in Si:P Double Quantum Dots
Solid-state systems such as P donors in Si have considerable potential for
realization of scalable quantum computation. Recent experimental work in this
area has focused on implanted Si:P double quantum dots (DQDs) that represent a
preliminary step towards the realization of single donor charge-based qubits.
This paper focuses on the techniques involved in analyzing the charge transfer
within such DQD devices and understanding the impact of fabrication parameters
on this process. We show that misalignment between the buried dots and surface
gates affects the charge transfer behavior and identify some of the challenges
posed by reducing the size of the metallic dot to the few donor regime.Comment: 11 pages, 7 figures, submitted to Nanotechnolog
Scalable design of an IMS cross-flow micro-generator/ion detector
Ion-mobility spectrometry (IMS) is an analytical technique used to separate
and identify ionized gas molecules based on their mobility in a carrier buffer
gas. Such methods come in a large variety of versions that currently allow ion
identification at and above the millimeter scale. Here, we present a design for
a cross-flow-IMS method able to generate and detect ions at the sub-millimeter
scale. We propose a novel ion focusing strategy and tested it in a prototype
device using Nitrogen as a sample gas, and also with simulations using four
different sample gases. By introducing an original lobular ion generation
localized to a few ten of microns and substantially simplifying the design, our
device is able to keep constant laminar flow conditions for high flow rates. In
this way, it avoids the turbulences in the gas flow, which would occur in other
ion-focusing cross-flow methods limiting their performance at the
sub-millimeter scale. Scalability of the proposed design can contribute to
improve resolving power and resolution of currently available cross-flow
methods.Comment: 14 pages, 10 figures, revised regular paper, minor correction
Selective, pulsed CVD of platinum on microfilament gas sensors
A post-processing, selective micro-chemical vapor deposition (``micro-CVD``) technology for the deposition of catalytic films on surface-micromachined, nitride-passivated polysilicon filaments has been investigated. Atmospheric pressure deposition of Pt on microfilaments was accomplished by thermal decomposition of Pt acetylacetonate; deposition occurs selectively only on those filaments which are electrically heated. Catalyst morphology, characterized by SEM, can be controlled by altering deposition time, filament temperature, and through the use of pulsed heating of the filament during deposition. Morphology plays an important role in determining the sensitivity of these devices when used as combustible gas sensors
Energy-efficient full-range oscillation analysis of parallel-plate electrostatically actuated MEMS resonators
This is the peer reviewed version of the following article: “Fargas Marques, A., Costa Castelló, R. (2017) Energy-efficient full-range oscillation analysis of parallel-plate electrostatically actuated MEMS resonators, 1-13.” which has been published in final form at [doi: 10.1007/s11071-017-3633-8]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."Electrostatic parallel-plate actuators are a common way of actuating microelectromechanical systems, both statically and dynamically. Nevertheless, actuation voltages and oscillations are limited by the nonlinearity of the actuator that leads to the pull-in phenomena. This work presents a new approach to obtain the electrostatic parallel-plate actuation voltage, which allows to freely select the desired frequency and amplitude of oscillation. Harmonic Balance analysis is used to determine the needed actuation voltage and to choose the most energy-efficient actuation frequency. Moreover, a new two-sided actuation approach is presented that allows to actuate the device in all the stable range using the Harmonic Balance Voltage.Peer ReviewedPostprint (author's final draft
Computational Prototyping Tools and Techniques
Contains reports on five research projects.Industry Consortium (Mobil, Statoil, DNV Software, Shell, OTRC, Petrobras, NorskHydro, Exxon, Chevron, SAGA, NSWC)U.S. Navy - Office of Naval ResearchAnalog DevicesDefense Advanced Research Projects Agency Contract J-FBI-95-215Cadence Design SystemsHarris SemiconductorMAFET ConsortiumMotorola SemiconductorDefense Advanced Research Projects AgencyMultiuniversity Research InitiativeSemiconductor Research CorporationIBM Corporatio
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