Neutron Detection Signatures at Zero Bias in Novel Semiconducting Boron Carbide/Pyridine Polymers

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 (B₁₀C₂H_x):(C₅NH_x)_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.