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ABSTRACT: We present a mechanical pressing technique for generating ultra-smooth surfaces on thin metal films by flattening the bumps,
asperities, rough grains and spikes of a freshly vacuum deposited metal film. The method was implemented by varying the applied
pressure from 100MPa to 600MPa on an e-beam evaporated silver film of thickness 1000Å deposited on double-polished (100)-oriented
silicon surfaces, resulting in a varying degree of film smoothness. The surface morphology of the thin film was studied using
atomic force microscopy. Notably, at a pressure of ∼600MPa an initial silver surface with 13-nm RMS roughness was plastically
deformed and transformed to an ultra-flat plane with better than 0.1nm RMS. Our demonstration with the e-beam evaporated
silver thin film exhibits the potential for applications in decreasing the scattering-induced losses in optical metamaterials,
plasmonic nanodevices and electrical shorts in molecular-scale electronic devices.
Applied Physics A 04/2012; 87(2):187-192. · 1.63 Impact Factor
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ABSTRACT: A new route to grow an ensemble of indium phosphide single-crystal semiconductor nanowires is described. Unlike conventional
epitaxial growth of single-crystal semiconductor films, the proposed route for growing semiconductor nanowires does not require
a single-crystal semiconductor substrate. In the proposed route, instead of using single-crystal semiconductor substrates
that are characterized by their long-range atomic ordering, a template layer that possesses short-range atomic ordering prepared
on a non-single-crystal substrate is employed. On the template layer, epitaxial information associated with its short-range
atomic ordering is available within an area that is comparable to that of a nanowire root. Thus the template layer locally
provides epitaxial information required for the growth of semiconductor nanowires. In the particular demonstration described
in this paper, hydrogenated silicon was used as a template layer for epitaxial growth of indium phosphide nanowires. The indium
phosphide nanowires grown on the hydrogenerated silicon template layer were found to be single crystal and optically active.
Simple photoconductors and pin-diodes were fabricated and tested with the view towards various optoelectronic device applications
where group III–V compound semiconductors are functionally integrated onto non-single-crystal platforms.
Applied Physics A 04/2012; 95(4):1005-1013. · 1.63 Impact Factor
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ABSTRACT: Development of devices that can be fabricated on amorphous substrates using multiple single-crystal semiconductors with different physical, electrical, and optical characteristics is important for highly efficient portable and flexible electronics, optoelectronics, and energy conversion devices. Reducing the use of single-crystal substrates can contribute to low-cost and environmentally benign devices covering a large area. We demonstrate a technique to harvest and transfer vertically aligned single-crystal semiconductor micro- and nanopillars from a single-crystal substrate to a low-cost carrier substrate while simultaneously preserving the integrity, order, shape, and fidelity of the transferred pillar arrays. The transfer technique facilitates multilayer process integration by exploiting a vertical embossing and lateral fracturing method using a spin-coated polymer layer on a carrier substrate. Electrical contacts are formed using a bilayer of metal and conducting polymer such as gold (Au) and polyaniline (PAni). In this method, the original single-crystal substrate can be repeatedly used for generating more devices and is minimally consumed, whereas in conventional fabrication methods, the substrate is employed solely as a mechanical support. This heterogeneous integration technique potentially offers devices with low physical fill factor contributing to lower leakage current and noise, reduced parasitic capacitance, and enhanced photon-semiconductor interactions, and enables heterogeneous multimaterial integration such as silicon with compound semiconductors for rapidly expanding large-scale applications, including low-cost and flexible electronics, displays, tactile sensors, and energy conversion systems.
IEEE Transactions on Electron Devices 09/2010; · 2.32 Impact Factor
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ABSTRACT: New discoveries in materials on the nanometer- length scale are expected to play an important role in addressing ongoing and future challenges in the field of communication. Devices and systems for ultra-high-speed short- and long-range communication links, portable and power-efficient computing devices, high-density memory and logics, ultra-fast interconnects, and autonomous and robust energy scavenging devices for accessing ambient intelligence and needed information will critically depend on the success of next-generation emerging nanomaterials and devices. This article presents some exciting recent developments in nanomaterials that have the potential to play a critical role in the development and transformation of future intelligent communication networks.
IEEE Communications Magazine 07/2010; · 3.79 Impact Factor
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V.J. Logeeswaran,
A. Sarkar,
M.S. Islam,
N.P. Kobayashi,
J. Straznicky,
Xuema Li,
Wei Wu,
Sagi Mathai,
M.R.T. Tan,
Shih-Yuan Wang,
R.S. Williams
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ABSTRACT: We demonstrate a high-speed polarization-insensitive photoconductor based on intersecting InP nanowires synthesized between
a pair of hydrogenated silicon electrodes deposited on amorphous SiO2 surfaces prepared on silicon substrates. A 14-ps full width at half maximum de-embedded impulse response is measured, which
is the fastest reported response for a photodetector fabricated using nanowires. The high-speed electrical signal measurements
from the photoconductor are performed by an integrated coplanar waveguide transmission line. The demonstrated ability to grow
intersecting InP nanowires on hydrogenated microcrystalline Si surfaces will facilitate the construction of ultra-fast photodetectors
on a wide range of substrates.
Applied Physics A 03/2008; 91(1):1-5. · 1.63 Impact Factor
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ABSTRACT: We describe the fabrication and characterization of photoconductors in which an ensemble of indium phosphide nanoneedles was utilized. DC electrical transport properties of the fabricated photoconductors were characterized under illumination with monochromatic light at 633 nm. This is the first demonstration of III-V compound semiconductor nanometerscale structures monolithically integrated on non-single crystalline silicon-based materials as an optoelectronic device that can be fabricated by a simple and flexible process not limited by single crystal substrates.
Nanotechnology, 2007. IEEE-NANO 2007. 7th IEEE Conference on; 09/2007
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ABSTRACT: We introduce a modulation mechanism for negative index materials (NIM) in the GHz frequency range by means of photoconductive
coupling. This leads the way to a monolithically integrated modulable NIM achieved by conventional microfabrication techniques.
The photosensitive material is deposited in the gap of the split ring resonator (SRR) structure and the response in terms
of S-parameters is simulated using a high frequency structure simulator (HFSSTM) program. Only a single SRR particle is simulated to demonstrate total suppression of resonance amplitude and without any
loss of generality the concept is applicable to a NIM comprising of both negative permeability and negative permittivity.
This simple modulation of refractive indices can lead to novel optical device developments with the potential to dramatically
improve the performance of existing phased array antennas, optical beam-forming networks, antenna remoting and transportation
of RF power through fiber.
Applied Physics A 04/2007; 87(2):209-216. · 1.63 Impact Factor
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ABSTRACT: For the study of miniature ion propulsion engine and electric wind devices, we have developed an electrohydrodynamically (EHD) driven microfabricated actuator. It consumes a maximum power of 100 mW and has a maximum resultant driving force of 0.45 μN in the first observed driving mode. The actuator consists of a mass/spring configuration fabricated with dual ion drives for propulsion. DC partial electrical discharge produces and accelerates the ions. Electric wind is generated by the momentum transfer from the ions to the air. Momentum is also transferred by virtue of the formation of intermittent space charge near the ionization zone. A selection between single and dual ion drives allows observation of various oscillation modes beginning at 896 Hz. The maximum out-of-plane oscillation amplitude measured was approximately 2 μm.
Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005
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ABSTRACT: This paper reports on the significant discrepancy between the analytical and experimental resonant frequencies of folded beam micro resonators. Experimental results for the resonant frequency showed a consistent 20% discrepancy over theoretical and finite element results. Possible causes of the discrepancy from tapered cross section of the flexure beams, dimensional variations and electrostatic spring effects are discussed and shown to contribute to the significant difference between analytical and experimental values. IntelliCAD(TM) electrostatic simulation was done to isolate the electrostatic spring effect and compared with the experimental observations. The compliance due to AC voltage has also been observed in DRIE resonators.
International Conference on Modeling and Simulation of Microsystems, Technical Proceedings; 01/2000
