Development of new radiation sensors for personal dosimetry

Seung Seob Lee, Purdue University

Abstract

Exposure to ionizing radiation occurs to those employed in a range of occupational settings. Current radiation protection regulations worldwide and in United States require that working individuals wear personal dosimeters to minimize exposure. Radiation protection practice is dominated by passive dosimeters; however, we anticipate that electronic dosimeters will be more widely adopted because of their advantages – e.g., real-time monitoring and alarming capabilities. MOS-based radiation sensors – conventional types of sensors employed in electronic dosimeters (e.g., RADFETs) – require continuous supply of large external biases; furthermore, their sensing capabilities are limited by the low frequency noise intrinsic to silicon. To develop external-bias-free MOS-based sensors, we created self-bias within MOS-based sensors with a sheet of charges artificially induced in the silicon dioxide layer. To overcome the intrinsic limitation of silicon, we also designed new radiation sensors incorporating promising sensing elements such as graphene and ZnO piezoelectric cantilever. This dissertation demonstrates the proof-of-principles of new sensor designs with experimental results and formulates theoretical models to optimize and compare the performance metric. Self-biasing with negative internal charges was found to be an effective method to boost the sensitivity. Our theoretical analyses suggested that graphene requires further reduction in noise levels to replace silicon; the ZnO piezoelectric cantilevers, on condition that a low bandwidth is available, promise a lower detection limit. Our new approaches – after overcoming some hurdles – are promising to strengthen radiation protection; therefore, future research to mature these technologies will be worthwhile.

Degree

Ph.D.

Advisors

Ziaie, Purdue University.

Subject Area

Electrical engineering

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