Collaborative Research: ARI-MA Development of Improved CMT and CZT Nuclear Detectors for Homeland Security Applications

The goal of this project is to develop high-resolution Cadmium Manganese Telluride (CMT) and Cadmium Zinc Telluride (CZT) materials for nuclear and radiological detection applications in homeland security. These materials have emerged as promising advanced detectors for X-ray and gamma-ray spectroscopy and imaging without cryogenic cooling. Advances in research have led to the development of CZT for commercial devices, but there is still the presence of defects such as Tellurium (Te) inclusions that limit the performance of large-volume CZT and CMT detectors that are needed for nuclear and radiological detection applications. The results of this project will provide benefit to society, with high impact on the science and technology of semiconductor nuclear detectors for room-temperature applications in homeland security (maritime and port security, border security, transportation security, nonproliferation and domestic nuclear security). The outcomes also include new capabilities that are very important to the success of emerging detector technologies and analysis tools needed to support next-generation nuclear materials management and safeguards. This project advances discovery and understanding while promoting teaching, training, and learning.

The project team will use theory-based design, knowledge-based processing and fabrication, and novel experimental techniques to develop improved cadmium manganese telluride (CMT) and cadmium zinc telluride (CZT) materials for high-resolution nuclear detection applications. The project will enhance the science and expand the overall knowledge in this area by using a combination of theory, modeling and experiments to complete the following tasks: 1) optimization of the Bridgman methods and Traveling Heater Method (THM) for growth of improved CMT and CZT crystals; 2) a novel post-growth annealing and doping process for removing performance-limiting defects caused by tellurium inclusions and associated impurities in CMT and CZT detector materials; and 3) improved surface passivation and detector fabrication techniques to produce better detectors. These methods employ state-of-the-art instrumentations that incorporate 3D-infrared transmission spectroscopy and advanced measurement tools to probe and collect data during the post-growth annealing process. The development of in-situ tools to monitor crystal annealing adds a new experimental dimension that will lead to any improved understanding of the migration of tellurium inclusions and novel methods to minimize their impact on electron trapping. The end result will be CMT and CZT detectors with better resolution, improved detection efficiency and better directional sensitivity.

The outcomes from the modeling aspects of this project will provide an understanding of fundamental phenomena associated with Bridgman and THM growth of ternary II-VI compounds and suggestions regarding post-growth treatments to improve the microstructural properties of these crystals. The anticipated impact of in-situ probing and data collection techniques will include new insights into the science and dynamical properties of post-growth annealing, uniform doping of detector materials, migration of Te secondary phases and impurities, and methods to process detector surfaces. This project advances discovery and understanding while promoting teaching, training, and learning. It is multidisciplinary with investigators from the following collaborating entities: Alabama A&M University, University of Minnesota ? Twin Cities, Brookhaven National Laboratory (BNL), FLIR Radiation Inc, and the Interdisciplinary Consortium for Research and Educational Access in Science and Engineering (INCREASE). The workforce development component of this project will provide opportunities for women and under-represented minorities to build careers and earn graduate degrees in areas critical to the development of cutting-edge nuclear and radiological detection technology.