Investigations of hexagonal boron nitride as a semiconductor for neutron detection

Abstract

The properties of hexagonal boron nitride (h-BN) as a semiconductor neutron detection medium were investigated. Single h-BN crystal domains were synthesized by the Chemical Engineering department at Kansas State University (KSU) using crystallization from molten metal solutions. At Texas Tech University (TTU), a detector was fabricated using epitaxial h-BN growth on a sapphire substrate where metallic micro-strip contacts 5 [mu]m apart and 5 nm thick where deposited onto the un-doped h-BN. In this research both the crystal domains synthesized at KSU and the detector fabricated at TTU were tested for neutron response. Neutron irradiation damage/effects were studied in pyrolytic h-BN by placing samples in the central thimble of the TRIGA MARK II reactor at KSU and irradiating at increasing neutron fluences. The domains synthesized at KSU as well as the detector fabricated at TTU showed no response to neutron activity on a MCA pulse height spectrum. Conductivity analysis showed abrupt increases in the conductivity of the pyrolytic h-BN at around a fluence of 10[superscript]1[superscript]4 neutrons per cm[superscript]2. Bandgap analysis by photoluminescence on the irradiated pyrolytic h-BN samples showed shifts in energy due to towards plane stacking disorders upon neutron irradiation. Future efforts may include the introduction of dopants in h-BN growth techniques for charge carrier transport improvement, and mitigation of plane stacking disorders.