378 research outputs found
Nanocluster-rich SiO2 layers produced by ion beam synthesis: electrical and optoelectronic properties
The aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism
Fabrication method for a room temperature hydrogen sensor
A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature
Printed inorganic transistors
Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2003.Includes bibliographical references (leaves 146-175).Forty years of exponential growth of semiconductor technology have been predicated on the miniaturization of the transistors that comprise integrated circuits. While complexity has greatly increased within a given area of processed silicon, the cost per area has not decreased. Current fabrication methods are further hindered by high facility costs and environmentally unfriendly processing. Moving to a new means of semiconductor fabrication may drastically reduce both financial and environmental costs. One such approach is based on the extension of printing techniques to the fabrication of electronic devices. Such printed electronics are envisioned to enable applications in flexible displays and electronic paper, personal fabrication, wearable computing, and disposable medical diagnostics. This dissertation focuses on the development of printable materials, specifically inorganic semiconductor inks. At the outset of this research, organic semiconductors were the only materials known and pursued as printable semiconductors. The ability to process organic semiconductors in common organic solvents makes them amenable to a wide range of printing technologies, but their electrical performance is fundamentally limited and their utility is confined to applications in which only low speeds are required. The goal of this thesis was to demonstrate the feasibility of printing inorganic materials, the same materials that are used to fabricate high quality semiconductor devices. Cadmium selenide was studied as a model inorganic semiconductor and silicon was studied because of its commercial dominance. The insolubility and high processing temperatures of inorganic semiconductors, both of which can prevent(cont.) their use in printed electronics, were overcome through the use of nanoparticle inks. At very small sizes, nanoparticles can be highly soluble in organic solvents and can have a pronounced melting point depression. Leveraging these size-dependent properties, the first semiconductor nanoparticle inks were developed using cadmium selenide and the first all-printed inorganic thin film transistors were demonstrated. Printed active layers in thin film transistors attained a semiconductor mobility of 1 cm²V⁻¹s⁻¹and an ON/OFF ratio in excess of 10⁴. Further development of inorganic nanoparticle inks and efforts to extend this approach to silicon are described, addressing silicon nanoparticle synthesis, purification, and ink formulation.Brent Ridley.Ph.D
Fabrication Method for a Room Temperature Hydrogen Sensor DIV
A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature
Room Temperature Hydrogen Sensor
A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature
Boron-incorporating silicon nanocrystals embedded in SiO2: absende of free carriers vs. B-induced defects
Boron (B) doping of silicon nanocrystals requires the incorporation of a B-atom on a lattice site of the quantum dot and its ionization at room temperature. In case of successful B-doping the majority carriers (holes) should quench the photoluminescence of Si nanocrystals via non-radiative Auger recombination. In addition, the holes should allow for a non-transient electrical current. However, on the bottom end of the nanoscale, both substitutional incorporation and ionization are subject to significant increase in their respective energies due to confinement and size effects. Nevertheless, successful B-doping of Si nanocrystals was reported for certain structural conditions. Here, we investigate B-doping for small, well-dispersed Si nanocrystals with low and moderate B-concentrations. While small amounts of B-atoms are incorporated into these nanocrystals, they hardly affect their optical or electrical properties. If the B-concentration exceeds ~1 at%, the luminescence quantum yield is significantly quenched, whereas electrical measurements do not reveal free carriers. This observation suggests a photoluminescence quenching mechanism based on B-induced defect states. By means of density functional theory calculations, we prove that B creates multiple states in the bandgap of Si and SiO2. We conclude that non-percolated ultra-small Si nanocrystals cannot be efficiently B-doped
Layer-by-layer nanoassembly combined with microfabrication techniques for microelectronics and microelectromechanical systems
The objective of this work is to investigate the combination of layer-by-layer self-assembly with microfabrication technology and its applications in microelectronics and MEMS.
One can assemble, on a standard silicon wafer, needed multilayers containing different nanoparticles and polymers and then apply various micromanufacturing techniques to form microdevices with nanostructured elements.
Alternate layer-by-layer self-assembly of linear polyions and colloidal silica at elevated temperatures have been firstly studied by QCM and SEM. LbL self-assembly and photolithography were combined to fabricate an indium resistor. The RTA method was employed in the fabrication. Hot-embossing technique as a reasonably fast and moderately expensive technique was used to replicate mold structures into thermoplastics. Microstamps with nanofeatures formed by this method can be applied on LbL nanoassembled multilayers. Finally, multiple ultrathin microcantilevers were developed by integrating LbL self-assembly, photolithography, wet etching, and ICP techniques. The purpose is to develop chemical/biosensor arrays for parallel, massive data gathering
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