Neutron Detection Signatures at Zero Bias in Novel Semiconducting Boron Carbide/Pyridine Polymers
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Neutron Detection Signatures at Zero Bias in Novel Semiconducting Boron Carbide/Pyridine Polymers Elena Echeverría1,†, Robinson James2,†, Frank L. Pasquale2,*, Juan A. Colón Santana3, M. Sky Driver2, A. Enders1, Jeffry A. Kelber2 and P.A. Dowben1 1 Department of Physics and Astronomy, University of Nebraska-Lincoln, 855 North 16th Street, Lincoln, NE 68588-0299, U.S.A. 2 Department of Chemistry, University of North Texas, 1155 Union Circle #305070, Denton, TX 76203, U.S.A. 3 Department of Physics, Northern Illinois University, DeKalb, IL 60115, U.S.A. † These authors contributed equally to this work. * Permanent address: Lam Research Corporation, PECVD Business Unit, 11155 SW Leveton Dr., Tualatin, OR 97062, U.S.A. ABSTRACT Novel and more conventional boron carbides were combined with n-type silicon to make heterojunction diodes, with neutron capture signal at zero applied bias. The boron carbides were based on the cross linking of closo-1,2-dicarbadodecaborane (ortho-carborane; 1,2-B10C2H12), and cross linking based on the combination of closo-1,2-dicarbadodecaborane (ortho-carborane; 1,2- B10C2H12) and pyridine. In the latter devices, pyridine concentration was varied; samples with a closo-1,2-dicarbadodecaborane (ortho-carborane; 1,2- B10C2H12) to pyridine ratio of 1:1 (BC:Py1) and 1:3 (BC:Py3). The result is a nonvolatile robust p-type semiconductor of boron carbide (B10C2Hx):(C5NHx)y. The I(V) curves for the resulting heterojunction diodes exhibit strong rectification where the normalized reverse bias leakage currents are largely unperturbed with increasing pyridine inclusion. The devices are largely gamma insensitive and yet neutron voltaic properties of these boron carbides is demonstrated. The neutron capture generated pulses from these heterojunction diodes were obtained at zero bias voltage although without the characteristic signatures of complete charge collection from boron neutron capture generated electron-hole pair production. These results, nonetheless, suggest that modifications to boron carbide may result in better neutron voltaic materials with linking groups chosen from family of aromatic compounds that stretch between borazine (B3N3H6) and benzene that point the way to a whole family of future studies that may ultimately lead to boron carbides better suited to low power and low flux neutron detection. INTRODUCTION One of the features of neutrons that make them interesting, but at the same time problematic to their detection, is the fact they have no charge, consequently, it is not possible to detect them directly. Currently, neutrons are identified through nuclear reactions, which create charged particles easily detected by radiation detectors. Therefore, elements with high capture cross section are desirable. However, there are really few elements with this characteristic that, additionally, can be made into solid state semiconductor neutron detectors. Boron has shown to
be suitable, and indeed semiconducting devices based on boron carbide films have attracted considerable attention for neut
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