Development of a radiation detector made of a cubic boron nitride polycrystal

Abstract

Radiation detectors were fabricated using single and polycrystalline cubic boron nitride crystals synthesized using a high-pressure and high-temperature method. Although cBN single crystals obtained using a barium BN solvent system were nearly colorless and displayed high electrical resistance, in contrast to conventional amber colored crystals, the single crystals exhibit a leakage current that renders them unsuitable for use in a detector. In contrast, a detector made of a cBN polycrystal synthesized by direct transformation had a very low leakage current of 0.2 pA with bias voltage of 100 V; it functioned as a radiation detector. From an experiment using alpha particles, holes traversed a longer distance than electrons. It had a fast rise time of approximately 300 ns. The detector also showed sensitivity to neutrons. However, output signals were smaller than the expected voltage from the experiment using alpha particles, probably because of charge accumulation from the high neutron flux.

Microstructure and Conduction Electron Quantum Properties of Small Diamond Cubic α-Sn Nanocrystals Embedded in Cubic Boron Nitride Crystals

“…One notices that for metals T 1 = T 2 , as the spin−spin interaction is relatively weak and the velocity of the conduction electrons on the Fermi surface is high. 38 Hence, the CESR linewidth directly measures the spin−lattice relaxation rate ΔB 1 ∼ 1/T 1 , which for simple metals is usually linear in temperature, probing the electron density of states at the Fermi level N(E F ) according to the Korringa law: 60 (6) For a Lorentzian ESR line, the relaxation time T 1 is related to the derivative peak-to-peak linewidth ΔB 1 through the general relation: (7) Here, γ e = eg e /2m e = 1.760859 × 10 11 s −1 T −1 is the electron gyromagnetic ratio. 61 Contributions to the spin−lattice relaxation process are usually expected from electron scattering by lattice vibrations, collision with lattice defects (including impurities), and α-Sn NC surface scattering.…”

“…Cubic boron nitride (cBN) with zinc blende structure is a wide band-gap (∼6.4 eV) semiconductor, industrially prepared as a crystalline superhard powder by the temperature gradient method, at high pressure and high temperature (HP-HT), in a variety of alkali or alkali-earth B-N solvents to which additives and/or catalysts are added. − Despite the cBN outstanding properties, − the presence, distribution, and atomic properties of the impurities incorporated in its crystal lattice are little known. The main reason is the extreme difficulty of preparing enough large (mm-sized), good quality single crystals with controlled impurity content, as required for physical investigations. − With recent advances in microanalysis and microstructural techniques using electron beams, , it is now possible to investigate the presence, nature, and aggregation state of the impurities incorporated in the submillimeter-sized cBN crystallites found in large-sized commercial superabrasive powders.…”