1,174 research outputs found

    FINITE ELEMENT AND IMAGING APPROACHES TO ANALYZE MULTISCALE ELECTROTHERMAL PHENOMENA

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    Electrothermal effects are crucial in the design and optimization of electronic devices. Thermoreflectance (TR) imaging enables transient thermal characterization at submicron to centimeter scales. Typically, finite element methods (FEM) are used to calculate the temperature profile in devices and ICs with complex geometry. By comparing theory and experiment, important material parameters and device characteristics are extracted. In this work we combine TR and FEM with image blurring/reconstruction techniques to improve electrothermal characterization of micron and nanoscale devices

    Biologically-Inspired Low-Light Vision Systems for Micro-Air Vehicle Applications

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    Various insect species such as the Megalopta genalis are able to visually stabilize and navigate at light levels in which individual photo-receptors may receive fewer than ten photons per second. They do so in cluttered forest environments with astonishing success while relying heavily on optic flow estimation. Such capabilities are nowhere near being met with current technology, in large part due to limitations of low-light vision systems. This dissertation presents a body of work that enhances the capabilities of visual sensing in photon-limited environments with an emphasis on low-light optic flow detection. We discuss the design and characterization of two optical sensors fabricated using complementary metal-oxide-semiconductor (CMOS) very large scale integration (VLSI) technology. The first is a frame-based, low-light, photon-counting camera module with which we demonstrate 1-D non-directional optic flow detection with fewer than 100 photons/pixel/frame. The second utilizes adaptive analog circuits to improve room-temperature short-wave infrared sensing capabilities. This work demonstrates a reduction in dark current of nearly two orders of magnitude and an improvement in signal-to-noise ratio of nearly 40dB when compared to similar, non-adaptive circuits. This dissertation also presents a novel simulation-based framework that enables benchmarking of optic flow algorithms in photon-limited environments. Using this framework we compare the performance of traditional optic flow processing algorithms to biologically-inspired algorithms thought to be used by flying insects such as the Megalopta genalis. This work serves to provide an understanding of what may be ultimately possible with optic flow sensors in low-light environments and informs the design of future low-light optic flow hardware

    CMOS camera employing a double junction active pixel

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    A New electronic image array: The Active pixel charge injection device

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    This is a Ph.D. thesis dissertation in which a new type of image sensor is investigated as possible successor to the charge coupled device (CCD) for scientific applications. As a result of the work described in this dissertation, the active pixel charge injection device (AP-CID) has been developed. This device retains most of the positive features of both the charge injection device (CJD) imager (random readout, non destructive readout, antiblooming, increased UV sensitivity, radiation tolerance, low power consumption, low manufacturing price) and the CCD imager (low noise, high dynamic range). The device lacks most of the drawbacks of the aforementioned devices. A functional array architecture was created. Based on this architecture several devices were fabricated. One of the arrays was fully measured, characterized and suggestions for improvement were formulated. Most of the characterizationalysis work described in this dissertation was centered on the following issues: temporal noise, linearity and FPN. The measured noise performance of the new device is excellent and comparable to the noise performance of the scientific CCD. The newly developed sensor is necessary for scientific imaging applications in space based operation. However due to its qualities, this device could be used in a much wider range of applications including commercial digital cameras, spectroscopy, biological, nuclear and other scientific applications

    An optical communications link

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    Includes bibliographical references.The thesis describes the development of a specification for, and prototypes of, an opto-electric voice communications link. The introductory sections deal with the generalised optical communications channel, the available hardware, and some of the research that has been done in the field. The information presented is used to motivate the type of system to be developed. The emphasis is placed on cost, though not as an overriding consideration. Modulation systems are examined, and frequency modulation of an m.f. subcarrier is chosen. The development of the practical system is covered in detail, in particular the receiver frontend circuitry. Considerable discrepancies between the design figures and actual measured performance are analysed, and their causes located. A practical mechanical design is presented, with suggested modifications for production. In conclusion, future developments in the field are examined

    DEVELOPING NANOPORE ELECTROMECHANICAL SENSORS WITH TRANSVERSE ELECTRODES FOR THE STUDY OF NANOPARTICLES/BIOMOLECULES

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    This study concerns development of a technology of utilizing metallic nanowires for a sensing element in nanofluidic single molecular (nanoparticle) sensors formed in plastic substrates to detect the translocation of single molecules through the nanochannel. We aimed to develop nanofluidic single molecular sensors in plastic substrates due to their scalability towards high through and low cost manufacturing for point-of-care applications. Despite significant research efforts recently on the technologies and applications of nanowires, using individual nanowires as electric sensing element in nanofluidic bioanalytic devices has not been realized yet. This dissertation work tackles several technical challenges involved in this development, which include reduction of nanowire agglomerates in the deposition of individual nanowires on a substrate, large scale alignment/assembly of metallic nanowires, placement of single nanowires on microelectrodes, characterization of electrical conductance of single nanowire, bonding of a cover plate to a substrate with patterned microelectrodes and nanowire electrodes. Overcoming the abovementioned challenges, we finally demonstrated a nanofluidic sensor with an in-plane nanowire electrode in poly(methyl methacrylate) substrates for sensing single biomolecules. In the first part of this study, we developed the processes for separation and large-scale assembly of individual NiFeCo nanowires grown using an electrodeposition process inside a porous alumina template. A method to fabricate microelectrode patterns on plastic substrates using flexible stencil masks was developed. We studied electrical and magnetic properties of new composite core-shell nanowires by measuring the electrical transport through individual nanowires. The core-shell nanowires were composed of a mechanically stable FeNiCo core and an ultrathin shell of a highly conductive Au gold (FeNiCo-Au nanowires). In the second part of this study, we simulated the effects of the nanopore geometry on the current drop signal of the translocation through a nanopore via finite element method using COMSOL. Using the above techniques, we developed for the fabrication and alignment of the microelectrodes and nanowires, we studied the optimum conditions to integrate the transverse nanoelectrode with the nanochannel on plastic substrates. The main challenge was to find the conditions to embed the micro-/nanoelectrodes into the nanochannel substrate as well as the nanochannel cover sheet

    A Bulk Driven Transimpedance CMOS Amplifier for SiPM Based Detection

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    The contribution of this work lies in the development of a bulk driven operationaltransconducctance amplifier which can be integrated with other analog circuits andphotodetectors in the same chip for compactness, miniaturization and reducing thepower. Silicon photomultipliers, also known as SiPMs, when coupled with scintillator materials are used in many imaging applications including nuclear detection. This thesis discuss the design of a bulk-driven transimpedance amplifier suitable for detectors where the front end is a SiPM. The amplifier was design and fabricated in a standard standard CMOS process and is suitable for integration with CMOS based SiPMs and commercially available SiPMs. Specifically, the amplifier was verified in simulations and experiment using circuit models for the SiPM. The bulk-driven amplifier’s performance, was compared to a commerciallyavailable amplifier with approximately the same open loop gain (70dB). Bothamplifiers were verified with two different light sources, a scintillator and a SiPM.The energy resolution using the bulk driven amplifier was 8.6% and was 14.2% forthe commercial amplifier indicating the suitability of the amplifier design for portable systems

    Sensing and Sensor Fundamentals

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    Vertical III-V Nanowire Transistors for Low-Power Electronics

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    Power dissipation has been the major challenge in the downscaling of transistor technology. Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have struggled to keep a low power consumption while still maintaining a high performance due to the low carrier mobilities of Si but also due to their inherent minimum inverse subthreshold slope (S ≥ 60 mV/dec) which is limited by thermionic emission. This thesis work studied the capabilities and limitations of III-V based vertical nanowire n-type Tunneling Field-Effect Transistor (TFET) and p-type MOSFET (PMOS). InAs/InGaAsSb/GaSb heterojunction was employed in the whole study. The main focus was to understand the influence of the device fabrication processes and the structural factors of the nanowires such as band alignment, composition and doping on the electrical performance of the TFET. Optimizations of the device processes including spacer technology improvement, Equivalent Oxide Thickness (EOT) downscaling, and gate underlap/overlap were explored utilizing structural characterizations. Systematic fine tuning of the band alignment of the tunnel junction resultedin achieving the best performing sub-40 mV/dec TFETs with S = 32 mV/decand ION = 4μA/μm for IOFF = 1 nA/μm at VDS = 0.3 V. The suitability of employing TFET for electronic applications at cryogenic temperatures has been explored utilizing experimental device data. The impact of the choice of heterostructure and dopant incorporation were investigated to identify the optimum operating temperature and voltage in different temperature regimes. A novel gate last process self-aligning the gate and drain contacts to the intrinsic and doped segments, respectively was developed for vertical InGaAsSb-GaAsSb core-shell nanowire transistors leading to the first sub-100 mV/dec PMOS with S = 75 mV/dec, significant ION/ IOFF = 104 and IMIN < 1 nA/μm at VDS = -0.5 V
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