We are exploring nanoelectronic engineering areas based on low dimensional materials, including carbon nanotubes and graphene. Our primary research focus is investigating carbon nanotube and graphene architectures for field emission applications, energy harvesting and sensing. In a second effort, we are developing a high-throughput desktop nanolithography process. Lastly, we are studying nanomechanical actuators and associated nanoscale measurement techniques for re-configurable arrayed nanostructures with applications in antennas, remote detectors, and biomedical nanorobots. The devices we fabricate, assemble, manipulate, and characterize potentially have a wide range of applications including those that emerge as sensors, detectors, system-on-a-chip, system-in-a-package, programmable logic controls, energy storage systems, and all-electronic systems.

At the Space Vehicles Directorate of the Air Force Research Laboratory, we are investigating detector concepts of use in Space Situational Awareness scenarios. For such applications, the object of interest is usually far away and often very dim. Our challenge becomes trying to identify such dim/distant space objects. To that end, we are investigating two optical signal amplification schemes and a wavelength-tunable detector scheme. One of the amplification schemes involves quantum interference in quantum dots in photonic crystal cavities, and one of the schemes involves near-field enhancements due to plasmonic interactions on patterned metal surfaces. The tunable detector scheme involves burying semiconductor quantum dots in one quantum well of a double-quantum-well structure, and then biasing the structure laterally.

Nanocrystalline ZnO films prepared by Pulsed Laser Deposition were used to fabricate the first thin film transistors that operate at microwave frequencies. Unlike more conventional amorphous Si and organic thin film transistors, which are only suitable for low speed applications, ZnO-based thin film transistors exhibit figure-of-merit device numbers that are comparable to single crystal transistors. These include on/off ratio of 10¹², current density of >400mA/mm and field effect mobility of 110 cm²/V.s. Parameters, including film growth temperature, gate insulators, and device layout designs were examined in detail to maximize performance. We have achieved current gain cut-off frequency, f_T, and power gain cut-off frequency, f_max, values of 2.9GHz and 10GHz, respectively with 1.2μm gate length devices demonstrating that ZnO-based TFTs are suitable for microwave applications.

Long photocarrier lifetime is a key issue for improving of room-temperature infrared photodetectors. Detectors based on nanostructures with quantum dot clusters have the strong potential to overcome the limitations in quantum well detectors due to various possibilities for engineering of specific kinetic and transport properties. Here we review photocarrier kinetics in traditional QDIPs and present results of our investigations related to the QD structures with vertically correlated dot clusters (VCDC). Modern technologies allow for fabrication of various VCDC with controllable parameters, such as the cluster size, a distance between clusters, dot occupation etc. Modeling of photocarrier kinetics in VCDC structures shows that the photocarrier capture time exponentially increases with increasing of the number of dots in a cluster. It also exponentially increases as the occupation of a dot increases. At the same time, the capture processes are weakly sensitive to geometrical parameters, such as the cluster size and the distance between clusters. Compared with ordinary quantum-dot structures, where the photoelectron lifetime at room temperatures is of the order of 1-10 ps, the VCDC structures allow for increasing the lifetime up to three orders of magnitude. We also study the nonlinear effects of the electric field and optimize operating regimes of photodetectors. Complex investigations of these structures pave the way for optimal design of the room-temperature QDIPs.

We report a voltage-tunable multispectral quantum dot infrared photodetector with integrated carbon-nanotube based flexible electronics. Such integrated photodetection and flexible electronics would not only enhance the detectors functionalities, but also reduce the time delay by performing image processing locally, making it promising for adaptive multi-spectral photodetection and sensing.

The past decade has seen a dramatic development in the infrared imaging systems. New material systems, novel fabrication schemes and creative read out circuit and system designs have all driven the third generation systems towards large format focal plane arrays with multicolor capability and high operating temperature. This paper explores the possibility of development of next generation infrared imagers. Could it be a bio-inspired infrared retina similar to the human eye? The conjecture is that the next generation systems will have two distinctive features that is present in the eye. They are (a) the ability to sense multimodal information including spectral, polarization, dynamic range, phase and (b) the intelligence to only send only small pieces of information to the central processing unit.

We have developed a number of amphiphilic polymers, comprised of a cluster of cholic acids (4 to 10) linked by a series of lysines and attached to one end of a linear polyethylene glycol chain (PEG, 2000-5000 Dalton). Under aqueous condition, such telodendrimers can self-assemble together with hydrophobic payloads to form highly stable micelles (15-150 nm diameter, size tunable). We used near infrared fluorescence (NIRF) optical imaging technique to study the in vivo passive accumulation of our nanocarriers (via EPR effect) in different types and stages of tumors. The results demonstrated that the micelle could preferentially accumulate in many types of tumor xenografts or synografts implanted in mice. Nanoparticle uptake in solid tumors was found to be much higher than that of lymphoma, which could be attributed to the relatively low microvascular density in the latter. We have also demonstrated that micelles smaller than 64 nm preferentially targeted xenografts with high efficiency and with low liver and lung uptake, whereas those micelles at 154 nm targeted the tumor poorly but with very high liver and lung uptake. Telodendrimers decorated with oligolysine or oligoaspartic acid resulted in high uptake of the nanoparticles into the liver. When decorated with cancer targeting ligands identified from the one-bead-one-compound (OBOC) combinatorial library methods, the drug-loaded nanoparticles were rapidly taken up by the target cultured tumor cells causing cell death. In vivo near infra-red optical imaging studies with hydrophobic fluorescent dye demonstrated that xenograft uptake of the micelles was greatly enhanced by the cancer targeting peptide.

The new "EXX" phenomena in macroscopic, microscopic and nanoscopic metal-semiconductor hybrid structures is described. Here E = extraordinary and XX = magnetoresistance (EMR), piezoconductance (EPC), optoconductance (EOC), and electroconductance (EEC). This new class of phenomena is based on the control and dominance of the geometric contributions, e.g. sample shape, lead placement, the presence of inhomogenieties, etc., to the transport properties of a physical system in contrast to traditional transport phenomena which are dominated by the intrinsic properties, e.g. mobility, carrier density, band structure, etc. The underlying phyiscs of EXX phenomena is elucidated with particular emphasis on the use of analytic and finite element analysis methods to quantitatively account for the observed EXX signal enhancement. The potential application of EXX phenomena to the study of the biologically relevant properties of cells such as surface charge density will be described.

There are critical implementation challenges to consider for new digital microfluidic technologies. In dynamic applications, properties of both the system and the microdroplet are changing in time due to the adsorption of microdroplet species at the solid-liquid and liquid-vapor interfaces. In this paper, these digital microfluidic dynamic challenges are overcome through the introduction of real-time sensing submodules. Dynamic sampling has been added to the actuation mechanisms of the digital microfluidic system, and it is shown that the complete fluid system can be characterized simultaneously by measurements of the microfluidic system capacitance and the microdroplet contact angle.

Stand-off detection of hazardous materials ensures that the responder is located at a safe distance from the suspected source. Remote detection and identification of hazardous materials can be accomplished using a highly sensitive and portable device, at significant distances downwind from the source or the threat. Optical sensing methods, in particular infrared absorption spectroscopy combined with quantum cascade lasers (QCLs), are highly suited for the detection of chemical substances since they enable rapid detection and are amenable for autonomous operation in a compact and rugged package. This talk will discuss the sensor systems developed at Pacific Northwest National Laboratory and will discuss the progress to reduce the size and power while maintaining sensitivity to enable stand-off detection of multiple chemicals.

Avoiding or minimizing potential damage from improvised explosive devices (IEDs) such as suicide, roadside, or vehicle bombs requires that the explosive device be detected and neutralized outside its effective blast radius. Only a few seconds may be available to both identify the device as hazardous and implement a response. As discussed in a study by the National Research Council, current technology is still far from capable of meeting these objectives. Conventional nitrocarbon explosive chemicals have very low vapor pressures, and any vapors are easily dispersed in air. Many pointdetection approaches rely on collecting trace solid residues from dust particles or surfaces. Practical approaches for standoff detection are yet to be developed. For the past 5 years, SRI International has been working toward development of a novel scheme for standoff detection of explosive chemicals that uses infrared (IR) laser evaporation of surfacebound explosive followed by ultraviolet (UV) laser photofragmentation of the explosive chemical vapor, and then UV laser-induced fluorescence (LIF) of nitric oxide. This method offers the potential of long standoff range (up to 100 m or more), high sensitivity (vaporized solid), simplicity (no spectrometer or library of reference spectra), and selectivity (only nitrocompounds).

Fielded surface detection systems rely on contact with either the liquid contamination itself or the associated chemical vapor above the contaminated surface and do not provide a standoff or remote detection capability. Conversely, standoff chemical vapor sensing techniques have not shown efficacy in detecting those contaminants as liquids or solids on surfaces. There are a number of optical or spectroscopic techniques that could be applied to this problem of standoff chemical detection on surfaces. The three techniques that have received the most interest and development are laser induced breakdown spectroscopy (LIBS), fluorescence, and Raman spectroscopy. Details will be presented on the development of these techniques and their applicability to detecting CBRNE contamination on surfaces.

With quality factors (Q) often-exceeding 10,000, vibrating micromechanical resonators have emerged as leading candidates for on-chip versions of high-Q resonators used in wireless communications systems. However, as in the case for transistors, extending the frequency of MEMS resonators generally entails scaling of resonator dimensions. Unfortunately, smaller size often coincides with lower-power handling capability and increased motional impedance. In this paper we introduce novel transduction techniques which can improve the motional impedance of MEMS resonators by 1000× over traditional 'air-gap' transduced resonators, present latest results on narrow-bandwidth parametric filters for frequency-agile radio receivers, and discuss performance scaling of NEMS resonators to X-band frequencies.

Miniaturization of mass-based resonant sensors is a promising strategy for chemical detection due to the increased sensitivity afforded by decreased length scales. However, while the increased surface area-to-volume ratios of microand nano-scale devices provide sensitivity benefits, smaller scales pose additional challenges in fabrication. We introduce the use of porous silicon resonators to provide increased sensitivity in resonant vapor sensors with minimal fabrication challenge. Standard top-down processes were used to fabricate micrometer-scale resonators with nanometerscale pores. The increased surface area of the porous resonating structures improved their detection sensitivity, and the porous nature of the resonator itself eliminated the need to apply porous coatings separate from the resonator. At present, porous silicon resonators show up to 100% sensitivity enhancement to isopropyl alcohol (vapor) over non-porous silicon resonators. Ongoing work involves investigating the limits of porosity and therefore sensitivity, the tradeoff between porosity and mechanical robustness, and the physics of resonant porous materials.

Graphene represents an important new material with potential Department of Defense sensor applications. At the Naval Research Laboratory we have developed three techniques to produce large-area graphene films. We have used this material to construct chemical and radio-frequency electromagnetic sensors. Here we report the initial results of this effort.

RF system front ends need to be mounted on a circuit board and interconnected to other devices such as antennas and surrounding circuitry functions. Providing suitable RF performing interconnects between or within devices on multi-layer construction has been done typically with doped semiconductors, copper, and occasionally other conductors. This paper discusses the use of organic printed circuit board MEMS switches and varactors, and the use of multi-wall carbon nanotubes as transmission lines and antennas. Carbon nanotube active transistors use single wall carbon nanotubes (SWCNT) with efforts to improve percentages of semiconducting structures. Interconnects are needed not only to connect CNT devices to each other, but to larger structures in order to be able to use subsystems that integrate CNT devices, large scale multifunction ICs, and RF devices used in RF front ends, including antennas. This paper addresses the use of organic substrates as the media for integration of MEMS, interconnects to devices on the substrate, and planar antennas. These methods will be required until complete assembly of all devices and interconnects can be done with processes at the nano-scale level, which is assumed to still need efficient radiative antenna structures at a larger scale for commonly used consumer wireless products.

We provide an overview of our work where carbon-based nanostructures have been applied to twodimensional (2D) planar and three-dimensional (3D) vertically-oriented nano-electro-mechanical (NEM) switches. In the first configuration, laterally oriented single-walled nanotubes (SWNTs) synthesized using thermal chemical vapor deposition (CVD) were implemented for forming bridge-type 2D NEMS switches, where switching voltages were on the order of a few volts. In the second configuration, vertically oriented carbon nanofibers (CNFs) synthesized using plasma-enhanced (PE) CVD have been explored for their potential application in 3D NEMS. We have performed nanomechanical measurements on such vertically oriented tubes using nanoindentation to determine the mechanical properties of the CNFs. Electrostatic switching was demonstrated in the CNFs synthesized on refractory metallic nitride substrates, where a nanoprobe was used as the actuating electrode inside a scanning-electron-microscope. The switching voltages were determined to be in the tens of volts range and van der Waals interactions at these length scales appeared significant, suggesting such structures are promising for nonvolatile memory applications. A finite element model was also developed to determine a theoretical pull-in voltage which was compared to experimental results.

Enzymes are commonly used as the active element in chemical sensors because of their analyte specificity, sensitivity, and the speed with which they catalyze reactions. Their precision and reliability has them at the core of many FDAapproved medical diagnostic tests. Unfortunately, nature has evolved most enzymes to operate under a fairly narrow range of storage and operating conditions (i.e. pH, ionic strength, temperature, organic content, etc). The deployment of enzyme-based sensors in poorly controlled environments with fluctuating conditions can therefore be difficult. ICx Technologies has sought to minimize the impact of environmental parameters on enzyme catalysis through enzyme polymerization. Rather than being simply immobilized onto an existing substrate, enzymes are used as co-monomers with other conventional monomers in polymerization reactions. Enzymes are incorporated within the polymer through multiple covalent attachments. By essentially anchoring the enzyme's tertiary structure, the polymerization process reduces enzyme sensitivity to many environmental factors. ICx has built a number of chemical sensors using enzyme polymers, some of which continuously monitor air or water in real time. The developed sensors have proven to operate well in many different environments.

A promising sensing technology utilizing AlGaN/GaN high electron mobility transistors (HEMTs) has been developed to analyze a wide variety of environmental and biological gases and liquids. The conducting 2DEG channel of GaN/AlGaN HEMTs is very close to the surface and extremely sensitive to adsorption of analytes. Examples of detecting mercury ions, perkinsus, lactic acid, carbon dioxide, and vitellogenin are discussed in this paper.

This paper presents a robust sensor to detect low concentration (<1 ppm) of CO gas. The sensor is based on AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Transistor (MOS-HEMT) with a non-conventional gate structure. The performance of the device has been simulated based on the charge control physics of AlGaN/GaN heterostructure transistor. Large sensitivities and widely linear characteristics are obtained for the AlGaN/GaN device based sensor assuming ideal gas-surface kinetics which can be approximated by the proposed gate structure. The sensor generates 0.8 μA of current for 0.5 ppm concentration of CO. The sensor shows linear characteristics for concentration of 1000 ppm CO. The effects of varying aspect ratio on total changes in current, sensitivity and linearity of the device have been simulated.

Aerospace applications require a range of chemical sensing technologies to monitor conditions related to both space exploration and aeronautic aircraft operations. These applications include leak detection, engine emissions monitoring, fire detection, human health monitoring, and environmental monitoring. This paper discusses efforts to produce microsensor platforms and Smart Sensor Systems that can be tailored to measure a range of chemical species. This technology development ranges from development of base sensor platforms to the evaluation of more mature systems in relevant environments. Although microsensor systems can have a significant impact on aerospace applications, extensive application testing is necessary for their long-term implementation. The introduction of nanomaterials into microsensor platforms has the potential to significantly enable improved sensor performance, but control of those nanostructures is necessary in order to achieve maximum benefits. Examples will be given of microsensor platform technology, Smart Sensor Systems, application testing, and efforts to integrate and control nanostructures into sensor structures.

Silicon Carbide (SiC) is a wide bandgap semiconductor with outstanding physical properties for manufacturing detectors of ionizing radiation (alpha, electrons, protons, X and gamma rays). The wide band gap (up to 3.2 eV), high saturation velocities of the charge carriers (2x10⁷ cm/s), high breakdown field (2 MV/cm), high thermal conductivity (4.9 W/cm²) and its radiation hardness, allow low-noise and reliable operation in environments which are critical or forbidden to other semiconductor detectors. In the last ten years, considerable R&D efforts have been devoted worldwide to growth and process technologies which have made available high purity epitaxial 2'' and 3'' SiC wafers. The state of the art of SiC micro-detector manufacturing technology will be presented together with prototype detectors with high resolution spectroscopic capabilities and outstanding low noise performance at room and high temperatures. The experimental characterization of different detector types (pad, pixel and microstrip) is shown and the radiation hardness of SiC detectors is discussed. X-ray spectroscopy with SiC will be presented: intrinsic line widths of 232 eV FWHM at +29°C and 336 eV FWHM at +100°C have been obtained using a SiC microstrip detector with 32 strips, 2 mm long and 25 μm, the recorded performance being fully limited by the noise of the front-end electronics. The necessity and the limits of ultimate low-noise front-end for reading out the Fano-limited SiC detectors are discussed.

We develop novel GaN-based high temperature and radiation-hard electronics to realize data acquisition electronics and transmitters suitable for operations in harsh planetary environments. In this paper, we discuss our research on AlGaN/GaN metal-oxide-semiconductor (MOS) transistors that are targeted for 500 °C operation and >2 Mrad radiation hardness. For the target device performance, we develop Schottky-free AlGaN/GaN MOS transistors, where a gate electrode is processed in a MOS layout using an Al₂O₃ gate dielectric layer. The AlGaN/GaN MOS transistors fabricated with the wide-bandgap gate oxide layer enable Schottky-free gate electrodes, resulting in a much reduced gate leakage current and an improved sub-threshold current than the current AlGaN/GaN field effect transistors. In this study, characterization of our AlGaN/GaN MOS transistors is carried out over the temperature range of 25°C to 500°C. The I_ds- V_gs and I_ds-V_ds curves measured as a function of temperature show an excellent pinch-off behavior up to 450°C. Off-state degradation is not observed up to 400 °C, but it becomes measurable at 450 °C. The off-state current is increased at 500 °C due to the gate leakage current, and the AlGaN/GaN MOS HEMT does not get pinched-off completely. Radiation hardness testing of the AlGaN/GaN MOS transistors is performed using a 50 MeV ⁶⁰Co gamma source to explore effects of TID (total ion dose). Excellent I_ds-V_gs and I_ds-V_ds characteristics are measured even after exposures to a TID of 2Mrad. A slight decrease of saturation current (ΔI_dss~3 mA/mm) is observed due to the 2Mrad irradiation.

Scaling down autonomous robotic systems introduces numerous challenges in mechanical design, electrical/sensor subsystems, and autonomous control. One particularly daunting task is the design of the power system, since this will ultimately limit all microrobot or micro-UAV's operations. Power sources like lithium polymer batteries possess sufficient power density for basic mobility (walking, fixed wing flight, flapping/hovering), but improved power sources are needed that offer increased energy density in order to extend mission lifetimes - preferably pushing from minutes to multiple hours or days. Additionally, the source power must be efficiently converted and distributed to the various microrobot subsystems. Each system may require a different voltage, current, and duty cycle. This paper will review some of the power-specific challenges related to developing small, mobile autonomous systems.

This paper explores the recent advances in circuit structures and design methodologies that have enabled ultra-low power sensing platforms and opened up a host of new applications. Central to this theme is the development of Near Threshold Computing (NTC) as a viable design space for low power sensing platforms. In this paradigm, the system's supply voltage is approximately equal to the threshold voltage of its transistors. Operating in this "near-threshold" region provides much of the energy savings previously demonstrated for subthreshold operation while offering more favorable performance and variability characteristics. This makes NTC applicable to a broad range of power-constrained computing segments including energy constrained sensing platforms. This paper explores the barriers to the adoption of NTC and describes current work aimed at overcoming these obstacles in the circuit design space.

This paper presents a discussion on sizing, weight and power of micro autonomous air and ground vehicles. While the air vehicles include both rotor and flapper based design, here the focus is on rotor based designs. The paper presents modeling methodologies for initial sizing of these vehicles and a survey of small COTS batteries. Some results from initial iterations on sizing vehicles and payloads are also presented. For air-vehicles, several factors have been identified in the sizing process, which can be adjusted in the search for a feasible design. These factors include the rotor figure of merit, the motor efficiency, and the battery specific energy. For ground vehicles, due to limited experimental data, three different ways for preliminary estimation of power requirements as a function of vehicle mass have been explored here. The sizing methodologies marry theoretical foundations with empirical observations and estimations.

Insensitivity to edge recombination is observed in GaAs-based InAs/InGaAs quantum dots-in-a-well (DWELL) solar cells by comparing their current-voltage (IV) plot to GaAs control samples. The edge recombination current component is extracted by analyzing devices of different areas and then compared to DWELL cells of comparable dimensions. The results demonstrate that GaAs-based solar cells incorporating a DWELL design are relatively insensitive to edge recombination by suppressing lateral diffusion of carriers in the intrinsic layer, and thus promising for applications that require small area devices such as concentration or flexible surfaces. Preliminary studies on the integration of these cells onto flexible surfaces such as Kapton and nanopaper are discussed including weight considerations for all the integrated materials.

The design of robots able to locomote effectively over a diversity of terrain requires detailed ground interaction models; unfortunately such models are lacking due to the complicated response of real world substrates which can yield and flow in response to loading. To advance our understanding of the relevant modeling and design issues, we conduct a comparative study of the performance of DASH and RoACH, two small, biologically inspired, six legged, lightweight (~10 cm, ~20 g) robots fabricated using the smart composite microstructure (SCM) process. We systematically examine performance of both robots on rigid and flowing substrates. Varying both ground properties and limb stride frequency, we investigate average speed, mean mechanical power and cost of transport, and stability. We find that robot performance and stability is sensitive to the physics of ground interaction: on hard ground kinetic energy must be managed to prevent yaw, pitch, and roll instability to maintain high performance, while on sand the fluidizing interaction leads to increased cost of transport and lower running speeds. We also observe that the characteristic limb morphology and kinematics of each robot result in distinct differences in their abilities to traverse different terrains. Our systematic studies are the first step toward developing models of interaction of limbs with complex terrain as well as developing improved limb morphologies and control strategies.

Micro Air Vehicles (MAVs) operate with many inter-related constraints, including size, weight, power, processing, and communications bandwidth. Basic equations can be used to provide initial estimates of subsystem parameters that are consistent with the targeted size and related parameters. For most current MAVs, the power source of choice is batteries, and the choice of battery type and size will determine the maximum duration of a flight. In this study, first order models for both rotary wing MAVs and crawling ground platforms are used to determine the optimum battery size for maximum endurance, given typical parameter values for a 15-cm scale robotic platform. Results indicate that most micro robotic platforms use battery sizes significantly different than optimum.

As part of our research for the ARL MAST CTA (Collaborative Technology Alliance) [1], we present an integrated architecture that facilitates the design of microautonomous robot platforms and missions, starting from initial design conception to actual deployment. The framework consists of four major components: design tools, mission-specification system (MissionLab), case-based reasoning system (CBR Expert), and a simulation environment (USARSim). The designer begins by using design tools to generate a space of missions, taking broad mission-specific objectives into account. For example, in a multi-robot reconnaissance task, the parameters varied include the number of robots used, mobility capabilities (e.g. maximum speeds), and sensor capabilities. The design tools are used to intelligently carve out the space of all possible parameter combinations to produce a smaller set of mission configurations. Quantitative assessment of this design space is then performed in simulation to determine which particular configuration would yield an effective team before actual deployment. MissionLab, a mission-specification platform, is used to incorporate the input parameters, generate the underlying robot missions, and control the robots in simulation. It also provides logging mechanisms to measure a range of quantitative performance metrics, such as mission completion rates, resource utilization, and time to completion, which are then used to determine the best configuration for a particular mission. These metrics can also provide guidance for the refinement of the entire design process. Finally, a case-based reasoning system allows users to maximize successful deployment of the robots by retrieving proven configurations and determine the robot capabilities necessary for success in a particular mission.

In today's world, consumer driven technology wants more portable electronic gadgets to be developed, and the next big thing in line is self-powered handheld devices. Therefore to reduce the power consumption as well as to supply sufficient power to run those devices, several critical technical challenges need to be overcome: a. Nanofabrication of macro/micro systems which incorporates the direct benefit of light weight (thus portability), low power consumption, faster response, higher sensitivity and batch production (low cost). b. Integration of advanced nano-materials to meet the performance/cost benefit trend. Nano-materials may offer new functionalities that were previously underutilized in the macro/micro dimension. c. Energy efficiency to reduce power consumption and to supply enough power to meet that low power demand. We present a pragmatic perspective on a self-powered integrated System on Chip (SoC). We envision the integrated device will have two objectives: low power consumption/dissipation and on-chip power generation for implementation into handheld or remote technologies for defense, space, harsh environments and medical applications. This paper provides insight on materials choices, intelligent circuit design, and CMOS compatible integration.

We use fiber-paper-supported carbon nanofoams as the basis for "multifunctional electrode nanoarchitectures" in which the nanofoams serve as conductive, ultraporous scaffoldings for subsequent incorporation of electroactive functionalities such as metal oxides, metal nanoparticles, and ultrathin polymers. The resulting functionalized carbon nanofoam papers are designed to serve as "plug-and-play" electrode structures in electrochemical devices ranging from high-rate Li-ion batteries and electrochemical capacitors to metal-air batteries and fuel cells. Electroless deposition is an attractive approach to functionalize structurally complex substrates, such as carbon nanofoams, and we have recently demonstrated that conformal nanoscopic coatings of manganese oxide (MnOx) can be generated on the exterior and interior surfaces of pre-formed carbon nanofoam papers via redox reaction with aqueous permanganate (MnO₄^-). The resulting nanoscale MnOx coatings provide not only faradaic charge-storage functionality to the nanofoam structure, but also enhanced electrocatalytic activity for molecular oxygen reduction. The electrocatalytic functionality of MnOx can now be combined with the desirable structural characteristics of carbon nanofoams (through-connected and size-tunable pore structures, high specific surface areas, and good electrical conductivity) to produce high-performance air-breathing cathodes for metal-air batteries. Herein, we report preliminary results for a particular series of native and MnOx-functionalized carbon nanofoams as examined for their O₂-reduction activity in a three-electrode testing configuration.

Pathways to scaling up the power and voltage output of on-chip micro-solid oxide fuel cells (μSOFC) have been investigated. μSOFC arrays consisting of one thousand three hundred and thirty-two (1332) membranes have been lithographically fabricated on 4" wafers. The membranes, with widths of ~150 μm, are comprised of 15-nm-thick La_0.6Sr_0.4Co_0.8F_0.2O₃ (LSCF) or 100-nm-thick porous Pt cathodes, 75-nm-thick Y_0.15Z_0.85O_1.93 (YSZ) electrolytes, and 100-nm-thick porous Pt anodes. Yield of fabrication is greater than 99% and only a few membranes failed after annealing at 500 °C. However, to reduce resistive loss, a current collector or a much thicker LSCF needs to be implemented if using LSCF as the cathode material on 4" wafers. Prototype components of μSOFC stacks for scaling up output voltage are also presented. The stacks require only two components - namely, a μSOFC plate and a bipolar separator - to form a repeating unit for the stacks. Flow channels and through silicon vias are integrated in the components. Challenges in fabrication and direction for further improvement for these approaches are discussed. The preliminary results suggest potential for further exploration into wafer-scale processing of fuel cell device structures for portable energy.

One-dimensional nanostructures have attracted considerable interest as potential building blocks and functional components in next generation nanoscale sensing, nanoelectromechanical systems (NEMS), circuits, and interconnect applications. The integration and assembly of one-dimensional nanostructures into such device architectures remains a significant challenge. Techniques for site-specific synthesis and self-assembly of one-dimensional nanostructures have proved suitable for a range of integrated nanostructure based-sensing applications yielding robust sensing capabilities realized with a streamlined fabrication process. Specifically, localized heating has emerged as a viable technique for the site specific synthesis of one-dimensional nanostructures. By localizing the heat source, the extent of chemical vapor deposition synthesis reactions can be confined to well-defined, microscale regions. Using the localized synthesis and self-assembly approach, proof-of-concept gas and pressure sensing applications have been demonstrated. The integration and self-assembly approach and sensing applications are described.

Electron tunneling between nanospaced electrodes provides a mechanism for directly transducing the presence of molecular analytes into electrical signals. Crossbar junctions with vertical separations on the order of a few nanometers were fabricated using a combination of electron-beam lithography and selective chemical etching. The current-voltage properties of the nanojunctions are highly sensitive to the chemical environment. The tunneling currents increase over one order of magnitude in response to water and organic vapors diluted with a background of pure nitrogen. The resistance of the junctions is also dependent on the concentration of the analyte. These results demonstrate that tunneling can be used to detect changes in the chemical environment.

We demonstrate anomalous gaseous field ionization and field desorption on branching intrinsic silicon nanowires grown by a two-step VLS technique. Field ionization and desorption I-V curves of argon, nitrogen, helium, and ammonia, were recorded individually within a wide pressure range (10^-7 to 10 Torr). Field ionization initiated at sub volt was followed by field desorption at about 7 - 38 V (applied field of ~ 7×10² to 3.8×10³ V/cm). Such voltages are three orders of magnitude smaller than the applied voltages required to generate field ionization on sharp metallic tips having the same tip curvature. The measured I-V curves were pressure dependent. Low voltage filed ionization and desorption phenomena were attributed to the combination effects of geometrical field enhancement on the apex of nanoscale silicon branches, field penetration, increased tunneling critical distance, band gap widening due to quantum confinement, and the surface states formed by the catalyst. The results presented herein suggest that gold terminated branching silicon nanowires could be strong candidates in building low power gas ionization sensors useful in highly selective detection of gases with low adsorption energies.

Thermoelectrics have been investigated for their cooling and energy harvesting uses over the last six decades. Those devices can be bought from a number of commercial suppliers. Thermotunneling (TT) devices, on the other hand, have been known only for the last two decades, and nobody has been able to practically manufacture or demonstrate the performance of those devices. In this study, we will discuss the high thermodynamic efficiency of these systems and design bottlenecks to reach the high efficiencies such as thermal back path and electrical losses. Concepts for possible device designs will be discussed in detail. Efficiency of those devices will be compared with the conventional power generation as well as solid-state power generation systems. Thermodynamic limits of TT systems will be compared, and first order economic analysis will be performed.

With the miniaturization of portable electronic devices, there is a demand for micro-power source which can be integrated on the semiconductor chips. Various micro-batteries have been developed in recent years to generate or store the energy that is needed by microsystems. Micro-supercapacitors are also developed recently to couple with microbatteries and energy harvesting microsystems and provide the peak power. Increasing the capacity per footprint area of micro-batteries and micro-supercapacitors is a great challenge. One promising route is the manufacturing of three dimensional (3D) structures for these micro-devices. In this paper, the recent advances in fabrication of 3D structure for micro-batteries and micro-supercapacitors are briefly reviewed.

The development of next-generation energy resources that are reliable and economically/environmentally acceptable is a key to harnessing and providing the resources essential for the life of mankind. Our research focuses on the development of novel semiconductor platforms that would significantly benefit energy harvesting, in particular, from light and heat. In these critical applications, traditional semiconductor solid-state devices, such as photovoltaic (PV) and thermoelectric (TE) devices based on a stack of single-crystal semiconductor thin films or single-crystal bulk semiconductor have several drawbacks, for instance; scalability-limits arise when ultra-large-scale implementation is envisioned for PV devices and performance-limits arise for TE devices in which the interplay of both electronic and phonon systems is important. In our research, various types of nanometer-scale semiconductor structures (e.g., nanowires and nanoparticles) coupled to or embedded within a micrometer-scale semiconductor structure (i.e., semiconductor nanomicrometer hybrid platforms) are explored to build a variety of non-conventional PV and TE devices. Two core projects are to develop semiconductor nano-micrometer hybrid platforms based on (1) an ensemble of single-crystal semiconductor nanowires connected to non-single-crystal semiconductor surfaces and (2) semimetallic nanoparticles embedded within a single-crystal semiconductor. The semiconductor nano-micrometer hybrid platforms are studied within the context of their basic electronic, optical, and thermal properties, which will be further assessed and validated by comparison with theoretical approaches to draw comprehensive pictures of physicochemical properties of these semiconductor platforms.

Energy is the ultimate currency that drives the world economy. Without energy, the global economy would cease to function normally. Most of the world's energy comes from the burning of fossil fuels such as coal and oil. Unfortunately, these fossil fuels are limited and pollute the atmosphere. The rising costs and demand of energy products and the alarming rate of global warming have focused research efforts into alternative forms of renewable energy. Thermoelectrics are one class of renewable energy producing devices. Thermoelectrics operate by converting temperature differences into electrical power and vice versa. They find limited use due to their low efficiencies and high cost. This article will review the operation of thermoelectrics and their current state-of-the-art. It will also explore future promising research endeavors that aim to increase their efficiency.

This paper reports cantilever-type nano-electro-mechanical systems (NEMS) silicon carbide (SiC) switches capable of operation from 25°C to 600°C, with threshold voltages ≤5 V. The fabricated SiC switches are actuated electrostatically, wherein the suspended cantilever electrode is pulled down to contact the bottom stationary electrode. The switches, fabricated using surface micromachining, have electrode separation gaps determined by the ~75 nm-thick sacrificial SiO₂. Two-terminal switches have been cycled more than 40 billion times at room temperature until failure and more than 2 million times at 600°C when the package wire bonds fail. The room temperature failure mechanisms of these switches are mechanical fracture and stiction. Stiction of the switch electrodes is strongly correlated to the roughness of their contacting surfaces. Measurements indicate that 60% of switches with 8 nm electrode surface roughness could be operated over billions cycles before fracture. In contrast, 85% of the switches with 1 nm roughness were stuck after fabrication release.

Most current capacitive RF-MEMS switch technology is based on conventional dielectric materials such as SiO₂ and Si₃N₄. However, they suffer not only from charging problems but also stiction problems leading to premature failure of an RF-MEMS switch. Ultrananocrystalline diamond (UNCD^(R) (2-5 nm grains) and nanocrystalline diamond (NCD) (10- 100 nm grains) films exhibit one of the highest Young's modulus (~ 980-1100 GPa) and demonstrated MEMS resonators with the highest quality factor (Q ≥10,000 in air for NCD) today, they also exhibit the lowest force of adhesion among MEMS/NEMS materials (~10 mJ/m²-close to van der Waals' attractive force for UNCD) demonstrated today. Finally, UNCD exhibits dielectric properties (fast discharge) superior to those of Si and SiO₂, as shown in this paper. Thus, UNCD and NCD films provide promising platform materials beyond Si for a new generation of important classes of high-performance MEMS/NEMS devices.

A major challenge associated with the demonstration of high frequency and fast NanoElectroMechanical Systems (NEMS) components is the ability to efficiently transduce the nanomechanical device. This work presents noteworthy opportunities associated with the scaling of piezoelectric aluminum nitride (AlN) films from the micro to the nano realm and their application to the making of efficient NEMS resonators and switches that can be directly interfaced with conventional electronics. Experimental data showing NEMS AlN resonators (250 nm thick with lateral features as small as 300 nm) vibrating at record-high frequencies approaching 10 GHz with Qs close to 500 are presented. These NEMS resonators could be employed as sensors to tag analyte concentrations that reach the part per trillion levels or for frequency synthesis and filtering in ultra-compact microwave transceivers. 100 nm thick AlN films have been used to fabricate NEMS actuators for mechanical computing applications. Experimental data confirming that bimorph nanopiezo- actuators have the same piezoelectric properties of microscale counterparts and can be adopted for the implementation of mechanical logic elements are presented.

Carbon materials, including carbon nanotubes and nanostructured diamond, have been investigated for over a decade for application to electron field emission devices. In particular, they have been investigated because of their low power consumption, potential for miniaturization, and robustness as field emission materials, all properties that make nanocarbon materials strong candidates for applications as long life electron sources for mass spectrometers for space exploration, where electron sources are exposed to harsh environments, .A miniaturized mass spectrometer under development for in situ chemical analysis on the moon and other planetary environments requires a robust, long-lived electron source, to generate ions from gaseous sample using electron impact ionization. To this end, we have explored the field emission properties and lifetime of nitrogen-incorporated ultrananocrystalline diamond films. We will present recent results revealing that UNCD films with nitrogen incorporation during growth (N-UNCD) yield stable/high fieldinduced electron emission in high vacuum for up to 1000 hours.

Having recently been demonstrated at frequencies over 1GHz with measured Q's>10,000^1-6, MEMS/NEMS resonators in silicon, SiC and CVD diamond structural materials have great potential for enabling resonant mass sensing down to zeptogram resolution as well as on-chip high-Q passives needed in wireless communication systems for frequency generation, translation and filtering. However, the acceptance of such devices for RF applications in present-day transceivers has been hindered so far by several remaining issues, including: (1) a frequency range lower than 5 GHz, (2) higher motional impedances than normally exhibited by macroscopic high-Q resonators, (3) limited linearity and power handling ability, and (4) insufficient frequency repeatability and stability. This paper reviews several material-centric strategies for alleviating the aforementioned issues. Given that resonance frequency is generally proportional to the acoustic velocity while energy dissipation and Q is also a strong function of the material properties, several deviceoriented and system-level performance-enhancing technologies will be discussed. Both capacitively-transduced and piezoelectrically-transduced resonators will be discussed with a particular emphasis on the employment of transducers with improved electromechanical coupling coefficient as the device-level method for lowering the motional impedance.

We present the design, fabrication, and characterization of a pixelated, hyperspectral arrayed component for Focal Plane Array (FPA) integration in the Long-Wave IR. This device contains tens of pixels within a single super-pixel which is tiled across the extent of the FPA. Each spectral pixel maps to a single FPA pixel with a spectral FWHM of 200nm. With this arrayed approach, remote sensing data may be accumulated with a non-scanning, "snapshot" imaging system. This technology is flexible with respect to individual pixel center wavelength and to pixel position within the array. Moreover, the entire pixel area has a single wavelength response, not the integrated linear response of a graded cavity thickness design. These requirements bar tilted, linear array technologies where the cavity length monotonically increases across the device.

EO/IR Sensors and imagers using nanostructure based materials are being developed for a variety of Defense Applications. In this paper, we will discuss recent modeling effort and the experimental work under way for development of next generation carbon nanostructure based infrared detectors and arrays. We will discuss detector concepts that will provide next generation high performance, high frame rate, and uncooled nano-bolometer for MWIR and LWIR bands. The critical technologies being developed include carbon nanostructure growth, characterization, optical and electronic properties that show the feasibility for IR detection. Experimental results on CNT nanostructures will be presented. We will discuss the path forward to demonstrate enhanced IR sensitivity and larger arrays.

Optical transport in planar waveguide structures is of great importance for spectroscopic chemical and biological sensing applications. We have fabricated a TiO₂-polymer planar waveguide with an embedded grating coupler. The grating coupler consists of a low index layer of SiO₂ on a Si(100) substrate. The SiO₂ layer has a grating pattern reactive ion etched into the surface. On top of this surface is a high index TiO₂ waveguide. The TiO₂ film is generated from a spincoated polymer solution, OptiNDEX^TM EXP04054 from Brewer Science. The TiO₂ film has low optical absorption, a high refractive index, and good thermal and UV stability. It is possible to make up to a 420nm film in a single coating operation. To form the TiO₂ film the polymer solution is spin-coated onto a wafer and the wafer is baked at 300 °C for 10 minutes. Scanning electron microscopy and focused ion beam cross-sections verified that the TiO₂ conformally fills the groves of the grating. We made electrodynamic calculations based on the indices of the materials for our waveguiding structure and the wavelength of the incident light for single-mode wave guiding. These calculations gave a projected TiO₂ thickness for our waveguides. Experimental results show that the waveguide structures that we fabricated were in close agreement with these predictions.

We present a system for secure identification applications that is based upon biometric-like MEMS chips. The MEMS chips have unique frequency signatures resulting from fabrication process variations. The MEMS chips possess something analogous to a "voiceprint". The chips are vacuum encapsulated, rugged, and suitable for low-cost, highvolume mass production. Furthermore, the fabrication process is fully integrated with standard CMOS fabrication methods. One is able to operate the MEMS-based identification system similarly to a conventional RFID system: the reader (essentially a custom network analyzer) detects the power reflected across a frequency spectrum from a MEMS chip in its vicinity. We demonstrate prototype "tags" - MEMS chips placed on a credit card-like substrate - to show how the system could be used in standard identification or authentication applications. We have integrated power scavenging to provide DC bias for the MEMS chips through the use of a 915 MHz source in the reader and a RF-DC conversion circuit on the tag. The system enables a high level of protection against typical RFID hacking attacks. There is no need for signal encryption, so back-end infrastructure is minimal. We believe this system would make a viable low-cost, high-security system for a variety of identification and authentication applications.

Quantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a strong characteristic spectral emission. This emission is tunable to a desired energy by selecting variable particle size, size distribution and composition of the nanocrystals. QDs have recently attracted enormous interest due to their unique photophysical properties and range of potential applications in photonics and biochemistry. The main aim of our work is develop new chiral quantum dots (QDs) and establish fundamental principles influencing their structure, properties and biosensing behaviour. Here we present the synthesis and characterisation of chiral CdSe semiconductor nanoparticles and their utilisation as new chiral biosensors. Penicillamine stabilised CdSe nanoparticles have shown both very strong and very broad luminescence spectra. Circular dichroism (CD) spectroscopy studies have revealed that the D- and Lpenicillamine stabilised CdSe QDs demonstrate circular dichroism and possess almost identical mirror images of CD signals. Studies of photoluminescence and CD spectra have shown that there is a clear relationship between defect emission and CD activity. We have also demonstrated that these new QDs can serve as fluorescent nanosensors for various chiral biomolecules including nucleic acids. These novel nanosensors can be potentially utilized for detection of various chiral biological and chemical species with the broad range of potential applications.

Nano and micro-structure electrode gaps were fabricated by an electroforming method. Thin film materials were fabricated on an insulator substrate and the microelectrodes with desired shapes were fabricated. Then the electroformation was carried out to produce the gap structure. Controllability of the size of these gaps was investigated by modeling and experimental method. It was found that the nanostructure of wide range of metal, metal oxides and compound semiconductors can be fabricated by this method. In this study, we have attempted formation of Al and Au. Simulation study was carried out based on finite element analysis (FEA) technique. The simulation results were verified with the experimental data.

Nanowire ensembles on non-single crystalline substrates are quickly becoming a popular active material moving towards commercial device production. In this study, ensembles of InP nanowires were grown by metal-organic chemical vapor deposition on non-single crystalline substrates. The samples are complicated by the presence of differing lattice types, geometries, crystal orientations and physical interaction that occurs in samples with high areal densities. The optical properties of the nanowires were studied by photoluminescence and Raman spectroscopy at various temperatures. The spectra are interpreted with particular emphasis on the above-mentioned complications.

The stability of silver nanoparticles on indium tin oxide coated glass substrates under atmospheric condition was investigated. These nanoparticles were fabricated using electron beam lithography. Energy dispersive spectroscopy analysis revealed a high concentration of sulfur in the silver nanoparticles exposed to laboratory air for 12 weeks at room temperature. Morphological changes in the silver nanoparticles were also observed for nanoparticles stored under the same conditions. In contrast, silver nanoparticles kept in vacuum did not show chemical or morphological changes after 12 weeks. The present work clearly shows the need to consider ambient exposure when using Ag nanoparticles for sensors.

Cantilever based sensors are promising miniaturized sensing tools for bio-chemical applications [1]. These micromechanical sensors can be employed to sense very small amounts of dangerous substances like explosive molecules, biological threats and hazardous compounds, both in air or liquid environment. In our project we focus on the development of a new readout system for employing of this sensing technique for detection of explosives like TNT, RDX and PETN, under the framework of the Xsense project. At present available optical equipments for cantilever sensing are typically big and bulky, making the in situ employment of this technology still very hard. Here we present a novel approach to measure the absorption of masses on the cantilever surfaces by using a light, compact, portable and high throughput optical device. Our setup is able to measure real time both the deflection of the beams and their vibrational frequencies, employing the same laser source and the same photodetector. The optical readout of cantilever-based sensors was re-designed and developed combining the technology of commercial DVD-ROM readers [2] with polymer based holding substrates structured with UV-lithography or imprint technology. Cantilever chips are clamped on a predefined holding substrate structured in SU-8 or in Cyclic Olefin Copolymer (COC), while the DVD-ROM reader is placed 1 mm below the substrate. The laser beam is collimated and focused on cantilevers with a 0.75 μm spot diameter and the reflected light is then recorded using an astigmatism-based 4-quadrant photodetector. The integration of the DVD-ROM reader with the on-substrate holding approach leads to a high throughput flexible platform with easy auto-alignment and replacement of the cantilevers chips. With this new on-substrate approach tens of chips can be placed on the Polymer holder and be read sequentially in a very light and compact device.

In this paper we demonstrate the potential for novel nanoporous framework materials (NFM) such as metal-organic frameworks (MOFs) to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable synthetic flexibility resulting from the presence of both organic and inorganic components within their structure. Detection of chemical weapons of mass destruction (CWMD), explosives, toxic industrial chemicals (TICs), and volatile organic compounds (VOCs) using micro-electro-mechanical-systems (MEMS) devices, such as microcantilevers and surface acoustic wave sensors, requires the use of recognition layers to impart selectivity. Traditional organic polymers are dense, impeding analyte uptake and slowing sensor response. The nanoporosity and ultrahigh surface areas of NFM enhance transport into and out of the NFM layer, improving response times, and their ordered structure enables structural tuning to impart selectivity. Here we describe experiments and modeling aimed at creating NFM layers tailored to the detection of water vapor, explosives, CWMD, and VOCs, and their integration with the surfaces of MEMS devices. Force field models show that a high degree of chemical selectivity is feasible. For example, using a suite of MOFs it should be possible to select for explosives vs. CWMD, VM vs. GA (nerve agents), and anthracene vs. naphthalene (VOCs). We will also demonstrate the integration of various NFM with the surfaces of MEMS devices and describe new synthetic methods developed to improve the quality of VFM coatings. Finally, MOF-coated MEMS devices show how temperature changes can be tuned to improve response times, selectivity, and sensitivity.

The research presented in this abstract pertains to nanowire-structured magnetic sensors fabricated by pulsed, template electrodeposition relying on giant magnetoresistance (GMR). System fabrication involves electrodepositing metals with a DC-biased square wave from a solution of iron-manganese solution into the porous aluminum oxide surface of an aluminum sheet. The chemical make-up of the resulting 20nm diameter, 500nm length nanowires was 6 at% manganese and 45 at% iron, which is desirable because the ferromagnetic layers (Fe) should be large in comparison with the nonmagnetic layers (Mn). The resulting nanowires exhibited a 73% drop in resistance when exposed to an external magnetic field.

A micro differential thermal analysis (DTA) system is used for detection of trace explosive particles. The DTA system consists of two silicon micro chips with integrated heaters and temperature sensors. One chip is used for reference and one for the measurement sample. The sensor is constructed as a small silicon nitride bridge incorporating heater elements and a temperature measurement resistor. In this manuscript the DTA system is described and tested by measuring calorimetric response of DNT (2,4-Dinitrotoluene). The design of the senor is described and the temperature uniformity investigated using finite element modelings and Raman temperature measurements. The functionality is tested using two different kinds of explosive deposition techniques and calorimetric responses are obtained. Under the framework of the Xsense project at the Technical University of Denmark (DTU) which combines four independent sensing techniques, these micro DNT sensors will be included in handheld explosives detectors with applications in homeland security and landmine clearance.

The simultaneous decrease in electronic device form factors yet increase in functionality has motivated a shift in energy storage design and manufacture to accommodate novel and unconventional materials, new device geometries, and nontraditional fabrication methods. We are developing a simple, low-cost, solution-based method for integrating custom energy storage components directly onto a device. A direct write dispenser printing system is used to pattern solutionsbased materials into multilayer devices. Along with this fabrication method, we discuss the materials design and device characterization of two printed energy storage devices: a carbon electrochemical microcapacitor and a zinc-metal oxide microbattery. The two components will be used as a hybrid energy storage system, capable of providing an energy dense storage buffer while also being able to address high power pulse loads, all within a limited footprint area.

Synthesis of carbon nanostructures at low temperature range of 600°C by a filament assisted chemical vapor deposition method was investigated. This system could be used to synthesis carbon nano-tubes, nano-fibers, and nano-helixes by changing the catalyst materials. The results indicated that the synthesis of these carbon structures with diameter from 20- 500 nm range is possible with the current method. It has been reported that random deposition of carbon helix structured in CVD of carbon nanotubes. This paper presents details of these experimental procedures.

Recently evolved THz technology opens up more possibilities for identification and characterization of different semiconductor crystal-based compounds. Since the THz waveform is essentially a direct manifestation of the crystal domain structure, the multicycle THz generation methods allow measuring of geometrical parameters of semiconductor internal structures as well as of dislocations and other structural defects. The above is useful for both characterization and identification of semiconductor materials. Further, methods of THz characterization of II-VI, III-V as well as tinary compounds are discussed. Computational techniques are suggested allowing the noise level reduction for the measurements.

Methanol is a hydrogen carrier for fuel cells and its chemical transformations are of great current interest. Methanol oxidation by vanadium oxides is well studied, hence, serves as a good measure for catalytic activity. Arrays of VO₂ nanowires grown on r-cut sapphire prove to be unique for the in situ catalytic activity tests. Here, we present size and morphology dependent activity of Platinum coated single crystalline VO₂ nanowires in methanol oxidation reactions using Grazing Incidence Small Angle X-ray Scattering (GISAXS). Our findings show an unexpected sintering behavior of Pt at temperatures as low as 200 °C.

High Q resonators are a critical component of stable, low-noise communication systems, radar, and precise timing applications such as atomic clocks. In electronic resonators based on Si integrated circuits, resistive losses increase as a result of the continued reduction in device dimensions, which decreases their Q values. On the other hand, due to the mechanical construct of bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators, such loss mechanisms are absent, enabling higher Q-values for both BAW and SAW resonators compared to their electronic counterparts.¹ The other advantages of mechanical resonators are their inherently higher radiation tolerance, a factor which makes them attractive for NASA's extreme environment planetary missions, for example to the Jovian environments where the radiation doses are at hostile levels.² Despite these advantages, both BAW and SAW resonators suffer from low resonant frequencies and they are also physically large which precludes their integration into miniaturized electronic systems.

In this article, an explicit formula is derived for determining appropriate number of simulation runs to estimate the parametric yield or violation probability of VLSI circuits. The formula involves no approximation and thus offers a rigorous control of the statistical error of estimation. Moreover, the formula is substantially less conservative than existing methods and hence can be used to avoid unnecessary computation. The application of the formula is illustrated by the timing analysis of an n-input NAND gate with a capacitive load.

EO/IR Nanosensors are being developed for a variety of Defense and Commercial Systems Applications. These include UV, Visible, NIR, MWIR and LWIR Nanotechnology based Sensors. The conventional SWIR Sensors use InGaAs based IR Focal Plane Array (FPA) that operate in 1.0-1.8 micron region. Similarly, MWIR Sensors use InSb or HgCdTe based FPA that is sensitive in 3-5 micron region. More recently, there is effort underway to evaluate low cost SiGe visible and near infrared band that covers from 0.4 to 1.6 micron. One of the critical technologies that will enhance the EO/IR sensor performance is the development of high quality nanostructure based antireflection coating. Prof. Fred Schubert and his group have used the TiO₂ and SiO₂ graded-index nanowires / nanorods deposited by oblique-angle deposition, and, for the first time, demonstrated their potential for antireflection coatings by virtually eliminating Fresnel reflection from an AlN-air interface over the UV band. This was achieved by controlling the refractive index of the TiO₂ and SiO₂ nanorod layers, down to a minimum value of n = 1.05, the lowest value so far reported. In this paper, we will discuss our modeling approach and experimental results for using oblique angle nanowires growth technique for extending the application for UV, Visible and NIR sensors and their utility for longer wavelength application.

The purpose of this work is to show that it is possible to excite selectively different resonant modes of a MEMS resonator, by simply changing some parameters in the feedback filter of Pulsed Digital Oscillators (PDOs). Extensive simulation and experimental results are presented showing the goodness of the proposed approach. An iterative map, contemplating more than one resonance, is also obtained from the equation governing the motion of a cantilever.

Metallic Sn-C composites were prepared by using electrospinning and electrostatic spray deposition (ESD). Morphology of the material prepared by these methods can be controlled by changing the experimental conditions such as the flow rate, voltage, composition of precursor solutions. Influence of the morphology on the electrochemical performance for the same composite was studied. Composite fibers prepared by electrospinning and porous films by ESD were characterized using X ray Diffraction, Transmission Electron Microscopy and Electrochemical characterization. Both the fibers and the porous composite films showed good performance compared to the tin nanopowder based anodes. Capacities of 760mAh/g and 686 mAh/g were obtained for Sn@C-hollow carbon nanofibers and Sn-C porous films, respectively.

This work introduces a new control method to dynamically mitigate the effects of the parasitic charge injected in dielectric layers of electrostatic MEMS switches. This method can be used to increase lifetime and reliability of electrostatically actuated MEMS devices. The method is based on the opposite behaviors exhibited by the dielectric charging phenomena when voltage stresses of different polarity are applied to a given device. To this effect, a sigmadelta sensing and actuation scheme has been implemented: device capacitance is periodically sampled and, according to the value obtained, positive or negative actuation voltages are applied. Preliminary experimental results with two different MEMS devices that demonstrate the feasibility of this method are introduced and discussed.

A metal-insulator-metal (MIM) tunneling diode having response time less than a picosecond (10^-12 second) is extremely important for mixers and detectors operating at terahertz and infrared frequencies. One of the key objectives of this work is to develop fabrication processes which are well-suited for mass production of nanogap MIM tunneling diodes with junction area in the range of 10^-2 μm² thus enabling the coveted terahertz frequencies due to the greatly reduced junction capacitance. A contemporary electron beam stepper of such resolution costs tens of millions and is not viable for mass production. This work employs standard photolithography and atomic layer deposition (ALD) methods, which allow formation of a micrometer-wide finger in the second metal layer that is separated from the first layer metal electrode by an ALD-deposited sidewall dielectric spacer, thus forming a nm-thick vertical tunneling junction. The junction area is defined by the width of the finger and the thickness of the electrode, while the junction thickness is controlled by the ALD deposited insulating layer. So far, by using a newly developed process, MIM tunneling diode with micron-scale self-aligned cross-fingers have been successfully demonstrated. Some preliminary DC characterizations have been carried out, and device characteristics such as responsivity, I-V, and C-V curves are documented. Ongoing research for modeling of MIM tunneling diode based on measured data and further reduction of the device junction area enabled by the new process will lead to MIM diode that could detect the infrared and terahertz spectra with greatly enhanced responsivity.

New energy harvesting technologies have drawn interest in recent years for both military and commercial applications. We present complete analysis of a novel device technology based on nanowire antennas and very high speed rectifiers (collectively called nanorectenna) to convert infrared and THz electromagnetic radiation into DC power. A nanowire antenna can receive electromagnetic waves and an integrated rectifier can convert them into electrical energy. The induced voltage and current distributions of nanowire antennas for different geometric parameters at various frequencies are investigated and analyzed. Also, nanowire antenna arrays with different geometries and distributions are examined. Moreover, novel nanoantennas are proposed for broadband operation and power conversion. All numerical computations are conducted using Ansoft HFSS. An incident plane wave was used to excite each device and simulations were carried out for frequencies between 0 and 200 THz. A voltage is induced in each device and it is measured in the thin oxide layer. Finally, optimum geometries of nanowires are proposed in order to maximize the amount of infrared power that is harvested.

Detection and quantification of very small amounts of biological species become necessary to allow an early detection of biothreats. Currently, fluorescence detection and colorimetry are the most frequently used techniques. Although very sensitive, the necessary labelling step of the biotargets can alter their recognition properties and these methods have a low potential for integration. This explains the constant effort of research on label-free detection methods. Onedimensional nanostructures, such as silicon nanowires, have emerged as good candidates for ultra-sensitive electrical detection of biological species. A silicon nanowire can operate as the channel of a field-effect transistor whose conductance is modulated by the change of charge of its surface due to the binding of biological species. A top-down fabrication process of silicon nanowire field effect transistors was developed on SOI and the influence of several physico-chemical parameters such as environmental electrostatic charges, light, buffer salinity and flow rate was evaluated. A change of the conductance of the Si nanowire according to the pH of the solution was demonstrated. Si nanowires were also tested as biosensors and allowed us to a better understanding of the involved phenomena. Complementary measurements are currently under progress.

We have investigated the feasibility of significantly improving the performance of currently favored uncooled infrared (IR) detectors based on Si or VO_x microbolometers with a new design employing freestanding suspended network of single-walled carbon nanotubes (SWCNTs). Such networks have high absorption coefficient, high temperature coefficient of the resistance (TCR) and extremely low thermal mass. This combination of parameters translates into an uncooled IR detector with high sensitivity and a very fast temporal response. We show estimates of key parameters for such a device, demonstrate a method to prepare it using suspended SWCNT networks achieved by selective removal of a sacrificial oxide layer, thereby forming a cavity under the SWCNT network. We also present TCR and photothermal bolometric response data of this conceptual structure.

Non-coding DNA comprises the majority of an organism's DNA and has the potential to store massive amounts of information. We hypothesize that information can be stored into non-coding DNA using a noisy mechanism comprised of thermally sensitive liposomes as sensors and measuring transport state variable information through DNA release and binding in response to stimuli. To test our hypothesis, we performed experiments that demonstrated the in situ, de novo synthesis of information-encoding DNA using natural biomaterials. Our results were compared to a lumped-parameter model designed to simulate the experiments. We found promising correlation between the DNA sequences generated by the simulations and those generated experimentally, suggesting that the in situ, de novo synthesized DNA does store recoverable information by the mechanism proposed.

Two non-rotating pumping components, a jet ejector and injector, were designed and tested. Two jet ejectors were designed and tested to induce a suction draft using a supersonic micronozzle. Three-dimensional axisymmetric nozzles were microfabricated to produce throat diameters of 187 μm and 733 μm with design expansion ratios near 2.5:1. The motive nozzles achieved design mass flow efficiencies above 95% compared to isentropic calculations. Ethanol vapor was used to motivate and entrain ambient air. Experimental data indicate that the ejector can produce a sufficient suction draft to satisfy both microengine mass flow and power off-take requirements to enable its substitution for high speed microscale pumping turbomachinery. An ethanol vapor driven injector component was designed and tested to pressurize feed liquid ethanol. The injector was supplied with 2.70 atmosphere ethanol vapor and pumped liquid ethanol up to a total pressure of 3.02 atmospheres. Dynamic pressure at the exit of the injector was computed by measuring the displacement of a cantilevered beam placed over the outlet stream. The injector employed a three-dimensional axisymmetric nozzle with a throat diameter of 733 μm and a three-dimensional converging axisymmetric nozzle. The experimental data indicate that the injector can pump feed liquid into a pressurized boiler, enabling small scale liquid pumping without any moving parts. Microscale injectors could enable microscale engines and rockets to satisfy pumping and feedheating requirements without high speed microscale turbomachinery.