School of Physics Thesis Dissertation Defense

Presenter:       Faris Almatouq

Title:                Synthesis and Characterization of Hexagonal Boron Nitride for Neutron Radiation Detection

Committee members:

Dr. Zhigang Jiang, School of Physics, Georgia Institute of Technology (advisor)

Dr. Walter de Heer, School of Physics, Georgia Institute of Technology

Dr. Phillip N. First, School of Physics, Georgia Institute of Technology 

Dr. Sharmistha Mukhopadhyay, School of Mechanical Engineering, Georgia Institute of Technology

Dr. Thomas Orlando, School of Chemistry and Biochemistry, Georgia Institute of Technology

Abstract: The assessment of radiation impact on astronauts during extravehicular activities is limited to post-mission analysis, using data collected and reported by dosimeter badges. This highlights the necessity for advancements in dosimeter technology, such as the development of systems capable of real-time radiation detection, to enhance the safety of astronauts from radiation exposure. This research focuses on developing such a technology by incorporating graphene field-effect transistors (gFETs) with monoisotopic hexagonal boron nitride (hBN).

The monoisotopic hBN studied in this work was synthesized in-house through a metal flux method using nickel and chromium. The hBN was characterized through various spectroscopic techniques, including Raman, photoluminescence, ultraviolet-visible absorbance, and X-ray diffraction, before and after exposure to neutron irradiation. The study used two types of neutron sources, a deuterium-deuterium neutron generator, and an Americium-Beryllium isotopic source, to observe the effects of neutron irradiation on hBN. It was found that neutron irradiation could induce specific defects in hBN, particularly the V_B^- defect. Then, monoisotopic hBN was transferred to a gFET to fabricate the proposed device. The resistance of the device was observed to increase in correlation with the total thermal neutron flux. This change in resistance can be attributed to the interaction between the device and alpha particles generated from thermal neutron capture by Boron-10. The ability of this device to detect changes in resistance under neutron irradiation in real time may offer a significant advancement in ensuring astronaut safety by providing real-time monitoring of neutron exposure, which is a critical aspect of cosmic radiation.