13 research outputs found

    21st Century Nanostructured Materials

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    Nanostructured materials (NMs) are attracting interest as low-dimensional materials in the high-tech era of the 21st century. Recently, nanomaterials have experienced breakthroughs in synthesis and industrial and biomedical applications. This book presents recent achievements related to NMs such as graphene, carbon nanotubes, plasmonic materials, metal nanowires, metal oxides, nanoparticles, metamaterials, nanofibers, and nanocomposites, along with their physical and chemical aspects. Additionally, the book discusses the potential uses of these nanomaterials in photodetectors, transistors, quantum technology, chemical sensors, energy storage, silk fibroin, composites, drug delivery, tissue engineering, and sustainable agriculture and environmental applications

    Ultra-thin and flexible CMOS technology: ISFET-based microsystem for biomedical applications

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    A new paradigm of silicon technology is the ultra-thin chip (UTC) technology and the emerging applications. Very thin integrated circuits (ICs) with through-silicon vias (TSVs) will allow the stacking and interconnection of multiple dies in a compact format allowing a migration towards three-dimensional ICs (3D-ICs). Also, extremely thin and therefore mechanically bendable silicon chips in conjunction with the emerging thin-film and organic semiconductor technologies will enhance the performance and functionality of large-area flexible electronic systems. However, UTC technology requires special attention related to the circuit design, fabrication, dicing and handling of ultra-thin chips as they have different physical properties compared to their bulky counterparts. Also, transistors and other active devices on UTCs experiencing variable bending stresses will suffer from the piezoresistive effect of silicon substrate which results in a shift of their operating point and therefore, an additional aspect should be considered during circuit design. This thesis tries to address some of these challenges related to UTC technology by focusing initially on modelling of transistors on mechanically bendable Si-UTCs. The developed behavioural models are a combination of mathematical equations and extracted parameters from BSIM4 and BSIM6 modified by a set of equations describing the bending-induced stresses on silicon. The transistor models are written in Verilog-A and compiled in Cadence Virtuoso environment where they were simulated at different bending conditions. To complement this, the verification of these models through experimental results is also presented. Two chips were designed using a 180 nm CMOS technology. The first chip includes nMOS and pMOS transistors with fixed channel width and two different channel lengths and two different channel orientations (0° and 90°) with respect to the wafer crystal orientation. The second chip includes inverter logic gates with different transistor sizes and orientations, as in the previous chip. Both chips were thinned down to ∼20m using dicing-before-grinding (DBG) prior to electrical characterisation at different bending conditions. Furthermore, this thesis presents the first reported fully integrated CMOS-based ISFET microsystem on UTC technology. The design of the integrated CMOS-based ISFET chip with 512 integrated on-chip ISFET sensors along with their read-out and digitisation scheme is presented. The integrated circuits (ICs) are thinned down to ∼30m and the bulky, as well as thinned ICs, are electrically and electrochemically characterised. Also, the thesis presents the first reported mechanically bendable CMOS-based ISFET device demonstrating that mechanical deformation of the die can result in drift compensation through the exploitation of the piezoresistive nature of silicon. Finally, this thesis presents the studies towards the development of on-chip reference electrodes and biodegradable and ultra-thin biosensors for the detection of neurotransmitters such as dopamine and serotonin

    Laboratory directed research and development. FY 1995 progress report

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    EUROSENSORS XVII : book of abstracts

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    Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

    Microscopy Conference 2017 (MC 2017) - Proceedings

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    Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

    Microscopy Conference 2017 (MC 2017) - Proceedings

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    Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

    Fabrication of Vanadium Dioxide Thin Films and their Structural, Optical and Electrical Characterization for Optoelectronic Applications

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    Vanadium dioxide (VO2) is a transition metal oxide that is well known for its metal-to-insulator phase transition (MIT). One of the most common forms of VO2 that has been generally studied is the thin film form. VO2 thin films are considered a strong candidate in various new-generation optical, electronic, and optoelectronic (photonic) applications. From the technology perspective, the fabrication of single-crystal VO2 thin films appears to be challenging. Up to now, research on the preparation of VO2 thin films has focused on employing different material fabrication techniques to produce high-quality VO2 thin films. The stoichiometry and quality of VO2 thin films strongly depend on the fabrication process. There is still a need to study the production of near-single-crystal, high-quality VO2 thin films and their structural, optical and electrical characterization. Secondly, the metal-to-insulator phase transition phenomenon in VO2 is a topical research field. The percolation theory has introduced some rigor in explaining the phase transition. This dissertation focuses on two aspects of research on VO2 thin films. The first aspect focuses on studying the effect of specific deposition parameters such as substrate biasing and substrate temperature on the quality of VO2 thin films. Also, the synthesis of high-quality VO2 thin films prepared on single-crystal silicon, quartz and sapphire substrates is investigated. The films are examined using various analysis techniques including Raman spectroscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDS). The optical constants, namely the refractive index (n) and the extinction coefficient (K), and the optical bandgap (Eg) of the films are extracted using the Swanepoel and Manifacier techniques. The second aspect of this dissertation covers the application of percolation theory on the phase transition in VO2 thin films. Accordingly, the topology of conducting clusters during the IMT and MIT is investigated by means of optical and electrical switching in a high-quality VO2 thin film. Additionally, self-heating-induced electrical and optical switching in VO2 thin films prepared on sapphire substrates under constant applied current pulses has been studied. The difference in the two switching dynamics is explained by a simple model based on the percolation theory
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