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High Temperature Characterization and Endurance Testing of Silicon Carbide Schottky Barrier Alpha Detectors

Jarrell, Joshua Taylor
http://rave.ohiolink.edu/etdc/view?acc_num=osu1420467919

Abstract Details

2015, Master of Science, Ohio State University, Nuclear Engineering.
Abstract There is a need for alpha detection systems which can operate in high temperature environments for long periods of time. The needs include the measurement of actinide concentrations in reprocessing of nuclear waste by means of pyroprocessing as well as in molten salt reactors. Silicon carbide is well suited to high temperature applications, has good corrosion resistance, has a wide band gap, and being a semiconductor material, when used on a particle detector exhibits high stopping power for charged particles in comparison to gas-filled detectors. As a result of these material properties, silicon carbide Schottky diodes are well suited to alpha particle detection and identification in high temperature environments. In this research, 4H-SiC alpha detectors with two different Schottky contact compositions were prepared and tested under various conditions. Each detector had either a nickel-titanium-gold Schottky contact or a platinum Schottky contact. The Schottky diode detectors had an ohmic nickel contact. Using an Am-241 alpha source in a vacuum chamber, the FWHM, diffusion length, and charge collection efficiency at varying voltages of each detector was determined and the behavior of these characteristics at temperatures from 20°C to 500°C was observed. The detectors were characterized using current-voltage, capacitance-voltage, and alpha spectroscopy measurements. The diffusion length was calculated as a free parameter during the charge collection efficiency calculation. Full charge collection was demonstrated at a bias voltage of -200 volts for nickel-titanium-gold detectors. The average FWHM for nickel-titanium-gold detectors was 3.5% (192 keV) for 5485 keV alpha particles at 500º Celsius with a peak resolution of 0.91% (50 keV). The FWHM for platinum Schottky contact detectors was found to be approximately 2% (110 keV) at the same incident alpha energy. Both types of detectors were subjected to long-term endurance testing at 500°C for a maximum of 168 hours. The change in performance of each detector was observed through analysis of the behavior of the FWHM, leading up to total failure of the device or end of the test period. Subsequent changes post cooling were observed as indicated by the current-voltage characterization taken at room temperature. Finally, a variation of the nickel-titanium-gold Schottky contact detectors was fabricated at a smaller diameter in order to reduce leakage current from the detector's surface. This variant displayed a greater resistance to long term high temperature operation than the larger nickel-titanium-gold detectors with which it was produced, but not greater than the resistance of the highest performing large detectors that were fabricated separately. The platinum Schottky contact detectors showed a higher charge collection at lower voltages, but would not be fully biased due to a breakdown of the internal potential prior to reaching full bias. Biasing at less than the full bias resulted in a less than total charge collection efficiency. Breakdown at a lower potential is indicative of the sensitivity of the detector's performance to changes in the Schottky barrier height which is dependent on material composition of the Schottky contact and the details of its fabrication.
Thomas Blue, Dr. (Advisor)
Lei Cao, Dr. (Committee Member)
91 p.
Electrical Engineering; Materials Science; Nuclear Engineering
SiC; alpha; detection; molten salt; Silicon Carbide; reprocessing; high temperature; pyroprocessing; actinide; radioisotopes; spectroscopy

Recommended Citations

Citations

  • Jarrell, J. T. (2015). High Temperature Characterization and Endurance Testing of Silicon Carbide Schottky Barrier Alpha Detectors [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420467919

    APA Style (7th edition)

  • Jarrell, Joshua. High Temperature Characterization and Endurance Testing of Silicon Carbide Schottky Barrier Alpha Detectors. 2015. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1420467919.

    MLA Style (8th edition)

  • Jarrell, Joshua. "High Temperature Characterization and Endurance Testing of Silicon Carbide Schottky Barrier Alpha Detectors." Master's thesis, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420467919

    Chicago Manual of Style (17th edition)

osu1420467919
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This open access ETD is published by The Ohio State University and OhioLINK.