III. Boron Carbide/polymer composites for neutron detection

Fig. 1 Zero bias neutron voltaic response for a PECVD boron carbide film (black) and 10:1 pyridine/boron carbide film (red). Neutron voltaic data courtesy of UNL. Semiconducting boron carbide films (B10C2Hx) formed from carborane icosahedra are of long-standing interest for neutron detection, due to the large 10B capture cross section for thermal neutrons.  The efficiency of such detectors is limited, however, by the poor and defect-dominated properties of B10C2Hx.  We have recently developed a novel class of materials consisting of orthocarborane/aromatic polymer composites, with aromatic species such as pyridine, benzene, diaminobenzene and polyaniline.  These films are deposited by plasma-enhanced chemical vapor deposition (PECVD) with tunable aromatic/carborane ratios and electronic structures [1].  A 10:1 pyridine:carborane film displays an 850% increase in sensitivity to thermal neutrons, relative to B10C2Hx, while remaining essentially gamma-blind (Fig. 1) [2, 3].  This enhanced sensitivity is apparently due to enhanced electron-hole separation [8] and charge transport. Other composites are being developed to further enhance such sensitivity, and these materials, which may have applications in photocatalysis and photovoltaics.

References

[1] R. James, F.L. Pasquale, J.A. Kelber. Plasma-enhanced chemical vapor deposition of ortho-carborane:  structural insights and interaction with Cu overlayers. J Phys:  Cond Matt 25 (2013) 355004.

[2] E. Echeverria, R. James, U. Chiluwal, F.L. Pasquale, J.A. Colon-Santana, R. Gapfizi, J. Tae, M. Driver, A. Enders, J. Kelber, P. Dowben. Novel semiconducting boron carbide polymers for neutron detection at zero bias. Appl Phys A. 118 (2015) 113.

[3] E. Echeverria, R. James, F.L. Pasquale, J.A. Colon-Santana, M.S. Driver, A. Enders, J.A. Kelber, P.A. Dowben. Neutron dectection signatures at zero bias in novel semiconducting boron Carbide/Pyridine polymers. Mater Res Soc Symp Proc. 1743 (2015) http://dx.doi.org/10.1557/opl.2015.352.

[4] F.L. Pasquale, R. James, R. Welch, E. Echeverria, P.A. Dowben, J.A. Kelber. Novel cross-linked ortho-carborane and ortho-carborane: Y (Y=1,4-diaminobenzene, pyridine, benzene) polymer films:  A new class of carborane-based materials with tunable electronic structure. ECS Trans. 53 (2013) 303-310