ADVANCED APPLICATIONS OF QUASI 1D OXIDES
Senior Investigator: Prof. Elisabetta Comini, Prof. Guido Faglia
New seed activities will be investigated, which exploit physical properties of quasi 1D oxides for the preparation of a new generation of devices with novel functional properties like electron field emission and gas detection through surface ionization. Besides intentional doping can greatly modify the device properties and yield new device applications other than electrodes in solar cells, like anodes for Li-ion batteries and in electrochemical biosensors, innovative thermoelectric materials for high temperature applications, interfacing with biological membranes.
- Quasi 1D oxides and CNT Electron Field Emission
- Surface ionisation gas detection
- Metal oxide NANOwires as efficient high-temperature THERmoelectric Materials
- Micro-photoluminescence imaging of single nanowires
Development in cold cathode based devices brought with it a need for more compact and economically viable electron sources capable of delivering high and stable current density at a low applied field. Field emission from 1D nanostructures exhibits great promise in this direction compared to the conventional microfabricated emitters. In collaboration with Gilardoni S.p.A. SENSOR will target the development of electron field emission sources for small and integrated X-ray sources. Many other applications in vacuum micro/nanoelectronics are foreseen.
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Metal oxide NANOwires as efficient high-temperature THERmoelectric Materials
The conversion efficiency of state of the art thermoelectric generators is limited to about 6%: higher performance low weight high-temperature thermoelectric materials than those that are currently in use are strongly needed. It has recently been shown that Si based quasi monodimensional 1D nanowires can be designed to achieve extremely large enhancements in thermoelectric efficiency, but only for low temperature (T<350K) thermoelectric. Quasi 1D metal oxide nanowires (MOX) would indeed provide the benefits of reduced dimensionality with their excellent durability at high temperatures and are formidable candidates to develop high-temperature thermoelectrics.
The objective is to assess the thermoelectric performances of quasi 1D MOX nanowires prepared by a simple and low cost evaporation condensation method and to build innovative thermoelectric modules to be employed in radioisotope thermoelectric generators and in the automotive industry in terms of fuel economy improvements by generating electricity from high temperature waste heat and enhancing air conditioning efficiency. Beside developed modules could have a significant impact on low power portable electronics.
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Micro-photoluminescence imaging of single nanowires
One of the most interesting materials used for nanostructure fabrication is the wide-bandgap semiconductor ZnO, which is a very attractive candidate for blue and UV optoelectronics. The investigation of a single nanowire – instead of mesh of nanowires with a wide diameter distribution – allows to better understand the properties of the material and to investigate the photoluminescence (PL) emission as a function of the nanowire diameter.
In our laboratory we investigate single crystalline nanowires (NWs) prepared by evaporation condensation technique and dispersed on SiO2 substrate.
Continuous-wave photoluminescence (PL) spectroscopy was carried out in a microscopic configuration by a Horiba modular micro-Raman system equipped with excitation source at 325 nm (He–Cd laser). PL spectra were acquired a microscope objective (40X UV and 50X Long Working Distance). Low temperature spectra were acquired by placing the sample in a Linkam THMS600 cell (temperature range 77K to 873K). Raman mapping with 442 nm and 532 nm is also available in our lab.
PL imaging of single nanowires showed that as the diameter of the wire decreased from 200 nm to 86 nm a 3 nm shift in the near band edge (NBE) PL is observed. PL of a single nanowire was investigated from room temperature (RT) to 77K, to reach insight on the mechanism responsible for PL emission of the nanowires.
