2 research outputs found
Novel Materials, Processing and Device Technologies for Space Exploration with Potential Dual-Use Applications
We highlight results of a broad spectrum of efforts on lower-temperature processing of nanomaterials, novel approaches to energy conversion, and environmentally rugged devices. Solution-processed quantum dots of copper indium chalcogenide semiconductors and multiwalled carbon nanotubes from lower-temperature spray pyrolysis are enabled by novel (precursor) chemistry. Metal-doped zinc oxide (ZnO) nanostructured components of photovoltaic cells have been grown in solution at low temperature on a conductive indium tin oxide substrate. Arrays of ZnO nanorods can be templated and decorated with various semiconductor and metallic nanoparticles. Utilizing ZnO in a more broadly defined energy conversion sense as photocatalysts, unwanted organic waste materials can potentially be repurposed. Current efforts on charge carrier dynamics in nanoscale electrode architectures used in photoelectrochemical cells for generating solar electricity and fuels are described. The objective is to develop oxide nanowire-based electrode architectures that exhibit improved charge separation, charge collection and allow for efficient light absorption. Investigation of the charge carrier transport and recombination properties of the electrodes will aid in the understanding of how nanowire architectures improve performance of electrodes for dye-sensitized solar cells. Nanomaterials can be incorporated in a number of advanced higher-performance (i.e. mass specific power) photovoltaic arrays. Advanced technologies for the deposition of 4H-silicon carbide are described. The use of novel precursors, advanced processing, and process studies, including modeling are discussed from the perspective of enhancing the performance of this promising material for enabling technologies such as solar electric propulsion. Potential impact(s) of these technologies for a variety of aerospace applications are highlighted throughout. Finally, examples are given of technologies with potential spin-offs for dual-use or terrestrial applications
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Wide bandgap semiconductor radiation detectors for extreme environments
Wide bandgap semiconductor photodiodes were investigated for their suitability as radiation detectors for high temperature applications (≥ 20 °C), through measurements, calculations of key parameters of the devices, and relating the results back to the material, geometry of the detectors, environment under which the detectors were investigated, and previously published work. Three families of photodiodes were examined.
4H-SiC vertical Schottky UV photodiodes with Ni2Si interdigitated contacts were characterised for their response under dark and UV illumination. Electrical characterisation up to 120 °C and room temperature responsivity measurements (210 nm to 380 nm) suggested that the devices could operate at low UV light intensities, even at high visible and IR backgrounds without the use of filters, and at high temperatures.
4H-SiC Schottky photodiode detector arrays with planar thin NiSi contacts were investigated for X-ray (≤ 35 keV) detection and photon counting spectroscopy at 33 °C. The electrical characterisation of the devices up to 140 °C and subsequent analysis suggested that the devices are likely to operate as high temperature X-ray spectrometers.
Results characterising GaAs p+-i-n+ mesa photodiode detectors for their room temperature visible and near infrared responsivity (580 nm to 870 nm), as well as their high temperature (≤ 60 °C) X-ray detection performance (at 5.9 keV) are presented. GaAs p+-i-n+ mesa photodiodes were also shown to be suitable for β- particle (electron) spectroscopy and X-ray fluorescence spectroscopy (≤ 21 keV) at 33 °C.
The X-ray and electron spectroscopic measurements were supported by a comprehensive treatment of the noise components in charge sensitive preamplifiers. Calculations showed the potential benefits of using a SiC, rather than Si, JFET as the input transistor of such a preamplifier operating at high temperatures. The spectroscopic measurements, using both the 4H-SiC and GaAs photodiodes, are presented along with noise analysis to detangle the different noise components present in the reported spectrometers, identify the dominant source of noise, and suggest potential improvements for future spectrometers using the reported devices