Fabrication of boron-phosphide neutron detectors

Abstract

Boron phosphide is a potentially viable candidate for high neutron flux neutron detectors. We have explored chemical vapor deposition methods to produce such detectors and have not been able to produce good boron phosphide coatings on silicon carbide substrates. However, semi-conducting quality films have been produced. Further testing is required. Background and Research ObjectivesLANL has an immediate opportunity to take the lead in the development of a new generation of neutron detectors. These detectors will be solid-state devices using the semiconductor boron-phosphide (BP) as the detection and charge collection medium. A collaboration between two small businesses, Devcom Inc. (manufacturers of CVD films) and RMD Inc. (manufacturers of radiation detectors), has recently demonstrated the detection of neutrons with a BP diode. In their diode, the thickness of the depletion layer was only lOpm, which is about 20 times smaller than required for efficient neutron detection. In order to make thicker depletion layers, the relationship between the electronic properties of BP t h i n -f i i with their synthesis, microstructures, and chemistry (impurity contents) needs to be understood. Since this problem is complex and interdisciplinary, Devcom and RMD need the assistance of a larger partner, like LANL, who has available a vast array of expertise and equipment.Work is to develop high quality BP semiconducting thin-films for use as neutron detectors.The value to the laboratory includes:The development of a new generation of neutron detectors that are efficient, inexpensive and capable of measuring high intensities, complements the objectivestated in the laboratory's Strategic Plan to develop a 1-MW spallation neutron. The CVD techniques developed to make high quality BP semiconductors might be utilized to fabricate thin-films of nanocrystalline BP, since nanocrystalline fidms of other materials (Ir and Rh) have been successfully fabricated using CVD (D.C.S.). Since nanocrystalline BP is anticipated to be mechanically strong, resistant to chemical attack and lightweight, this material has commercial potential as a tribological coating and is of interest to the lab's Advanced Materials and Processes initiative in. Our project complements this interest.