A5029136014- Additive Manufacturing and 3D Printing Technologies
- Near-Field Optical Microscopy
- Force Microscopy Techniques and Applications
- Phase-change materials and chalcogenides
- Integrated Circuits and Semiconductor Failure Analysis
- Powder Metallurgy Techniques and Materials
- Advanced materials and composites
- Manufacturing Process and Optimization
- Acoustic Wave Resonator Technologies
- Cholinesterase and Neurodegenerative Diseases
- Pesticide Exposure and Toxicity
- Machine Learning in Materials Science
- Electronic Packaging and Soldering Technologies
- Microwave and Dielectric Measurement Techniques
- Mechanical and Optical Resonators
- Ultrasonics and Acoustic Wave Propagation
- Combustion and flame dynamics
- Granular flow and fluidized beds
- Metal-Organic Frameworks: Synthesis and Applications
- Cellular and Composite Structures
- Insect and Pesticide Research
- Optical and Acousto-Optic Technologies
- Ferroelectric and Piezoelectric Materials
- Electrical and Thermal Properties of Materials
- Particle Dynamics in Fluid Flows
Stanford University
2015-2022
Sandia National Laboratories California
1982-2015
Delft University of Technology
2013
Walter Reed Army Institute of Research
2005-2008
Georgia Institute of Technology
2006
Mississippi State University
2006
University of Wollongong
2003
Metal-organic frameworks (MOFs) are crystalline nanoporous materials comprised of organic electron donors linked to metal ions by strong coordination bonds. Applications such as gas storage and separations currently receiving considerable attention, but if the unique properties MOFs could be extended electronics, magnetics, photonics, impact on material science would greatly increase. Recently, we obtained "emergent properties," electronic conductivity energy transfer, infiltrating MOF pores...
Many chalcogenide glasses undergo a breakdown in electronic resistance above critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization emerging phase-change memory. Purely well crystal nucleation assisted models have been employed to explain the breakdown. Here, picosecond electric pulses are used excite amorphous Ag$_4$In$_3$Sb$_{67}$Te$_{26}$. Field-dependent reversible changes conductivity and pulse-driven observed. The present results...
A general approach for calculating tip-sample capacitance variation in near-field scanning microwave microscopy is presented. It can be applied to arbitrary tip shapes, thick and thin films, due inhomogeneous perturbation. The computation domain the interaction problem reduced a block perturbation area by applying Green's theorem, thus it save substantial time memory during either electric field or contrast three-dimensional models of microscopy. We show that this method accurately calculate...
In this paper, design, fabrication, assembly and testing of unique high read-range high-efficiency (95%) radio frequency identification (RFID) antenna for the 915 MHZ UHF band are discussed. The exceptional characteristics RFID investigated in terms antenna-IC matching radiation efficiency. MHz passive tag is a 3" times omnidirectional yielded read range 31 feet compared to 4" leading commercial design 26 tested lab. This also possesses higher power (-7dBm 30 dBm) than (-5dBm dBm). proposed...
Abstract: A unit truss finite element analysis method allowing non-linear deformation is employed to analyze a cell comprised of n octet-truss structures for their stiffness and displacement compared relative density under loading. Axial, bending, shearing, torsion effects are included in the each strut structure which then related mesostructure level (unit cell). The versatility additive manufacturing allows fabrication these complex can be used as building blocks macro-scale geometries....
This paper was presented at the Proceedings of The Seventeenth Solid Freeform Fabrication Symposium Austin, TX, August 14-16, 2006.
ABSTRACT Three‐dimensional finite element simulations were performed to study the growth of microstructurally small fatigue cracks in aluminium alloy 7075‐T651. Fatigue crack propagation through five different crystallographic orientations was simulated using crystal plasticity theory, and plasticity‐induced opening stresses calculated. The computed used construct d a /d N ‐Δ K diagrams. generated curves compared well with experimental data from literature. variance observed among results,...
Resistors have several applications in high frequency circuits including uses attenuators, terminations, and power dividers among others. To date, there has been very little attempt to characterize embedded resistor performance on organics above 18 GHz. In this paper, RF measurements of thin film resistors up 40 GHz are presented a liquid crystal polymer (LCP) substrate using commercially available laminated foil form the NiCrAlSi resistors. Measurements demonstrated be accurate 5% their...
Scanning Microwave Impedance Microscopy (MIM) measurement of photoconductivity with 50 nm resolution is demonstrated using a modulated optical source. The use source allows for in single scan without reference region on the sample, as well removing most topographical artifacts and enhancing signal to noise compared unmodulated measurement. A broadband light tunable monochrometer then used measure energy resolved same methodology. Finally, pulsed local photo-carrier lifetimes via MIM, tip.
A quantitative approach is used to determine an effective height of probe beyond which the capacitance contribution not significant in microwave impedance microscopy (MIM). We compare for three different modes measurement, i.e., C(l) (l tip-sample distance), derivative (C'(l)), and second (C″(l)). discuss effects tip geometry sample properties such as relative permittivity on with examples analyze implication spatial resolution MIM. Finally, our results are verified by (MIM) measurement.
We report fast readout of the motion a carbon nanotube mechanical resonator. A close-proximity high electron mobility transistor amplifier is used to increase bandwidth measurement displacements from kHz MHz regime. Using an electrical detection scheme with acting as mixer, we detect amplitude its at room temperature intermediate frequency 6 and timeconstant 780 ns, both up five orders magnitude faster than achieved before. The transient response indicates ring-down time our enhanced...
Surface Acoustic Wave (SAW) resonances were imaged within a closed domain in the ferroelectric LiTaO$_3$ via scanning Microwave Impedance Microscopy (MIM). The MIM probe is used for both SAW generation and measurement, allowing contact-less measurement mesoscopic structure. Measurements taken over range of microwave frequencies are consistent with constant acoustic velocity, demonstrating nature measurement.
The proposed X-ray spatial light modulator (SLM) concept is based on the difference of scattering from amorphous and crystalline regions phase change materials (PCMs) such as Ge 2 Sb Te 5 (GST). In our SLM design, “ on” off” states correspond to a patterned homogeneous state GST thin film, respectively. obtained by exposing film laser pulses. this paper, we present patterning results in films characterized microwave impedance microscopy small-angle at Stanford Synchrotron Radiation Lightsource.
A variety of experimental diagnostic techniques are being developed to investigate the physical and chemical processes that occur in internal combustion engines. These optical diagnostics have been applied critical problems arising development direct-injection stratified-charge, diesel, lean-homogeneous charge The results presented illustrate (1) application laser velocimetry measure fluid flow, (2) spontaneous Raman scattering time- space-resolved temperature species concentration, (3) for...
The measurement of inhomogeneous conductivity in optically crystallized, amorphous Ge2Sb2Te5 (GST) films is demonstrated via scanning microwave impedance microscopy (MIM). Qualitative consistency with expectations spots crystallized by focused coherent light at various intensities, exposure times, and film thicknesses. characterization process imperfections when a mask used to pattern the nanoscale features crystalline GST film. These measurements show ability MIM resolve partial...
these diagnostic techniques.12 In the second part, three different approaches to modeling of turbulent reacting flows are discussed. These include moment, probability density function, and vortex dynamics approaches. Model predictions some portions experimental results described in first part paper discussed, as other chemically documented literature. Most comparisons between measurements have not been previously published.
Financial support for this work is provided by the Office of Naval Research, Contract #N00014-C-00-0378.
Financial support for this work is provided by the Office of Naval Research, Contract #N00014-C-00-0378.
Amorphous chalcogenides undergo a sharp increase in conductivity upon application of strong electric field, called threshold switching. Here, we show evidence for switching driven by picosecond terahertz-frequency field pulses.