Research Project
9908694
1 The high spatial-resolution and energy-resolution of cadmium zinc telluride (CZT) and cadmium telluride 2 (CdTe), compared to that of scintillators, offers superior image quality in Nuclear medicine and X-ray 3 imaging applications, i.e. SPECT, PET, CT, Bone Densitometry, Oncology, Dental imaging, Airport 4 security, etc. Even after two decades of research, CZT and CdTe remain the desired choice for room- 5 temperature radiation detection, but it is limited by high-cost and availability resulting from low yield and 6 long production times associated with commercial growth techniques, i.e. the Traveling Heater Method 7 (THM). However, the application of the Accelerated Crucible Rotation Technique by Modified Vertical 8 Bridgman (ACRT-MVB) growth method at WSU has proven to produce industrial quality, high- 9 performance CZT/CdTe. This new growth method not only allows CZT/CdTe to be grown with the same 10 quality as material grown by THM, but also at growth rates approximately 10-20 times faster than THM. 11 Specifically, CZT/CdTe is grown by THM at a rate of approximately 1-3 mm per day, whereas CZT/CdTe 12 growth by ACRT-MVB can be accomplished at much faster rates of approximately 1-2 mm per hour. 13 CZT/CdTe crystal growth in the current commercial methods, the Traveler Heater Method (THM), requires 14 a lower growth temperature for high-quality devices, which results in highly off-stoichiometric melts, 15 thereby inducing the need for postprocessing. These major challenges associated with the crystal growth of 16 CZT/CdTe have been overcome using ACRT-MVB. Improving and reproducing the single-crystal yield of 17 commercial grade CZT/CdTe is the next critical step. Recently, considerable improvement in the single- 18 crystal yield has been achieved by WSU when grown under off-stoichiometric (3.5%-5% excess Te) 19 conditions. An optimization in terms of rotation profile, temperature profile, and Te concentration will be 20 performed to improve the yield while retaining the superior device performance in Phase I efforts. In Phase 21 II, this technology will be transferred from WSU to RDT. The medical/diagnostic imaging market is 22 projected to cross $55.7 billion by 2025. Stakeholders in the medical imaging market need CZT/CdTe 23 devices now, especially devices that are capable of high count-rate imaging applications ? a focus in this 24 Phase I effort. The fruition of this project will be the significant reduction (>3x) of industrial-grade material 25 costs by increasing the yield, reducing the growth time, and eliminating post-growth anneal treatments 26 currently used by industry. With the fast-production time and high-performance of the CZT/CdTe produced 27 in this effort, (1) the medical imaging market will finally have a fast turnaround time and consistent high- 28 performance material that can easily be obtained, (2) a >3x price reduction is projected for CZT/CdTe, and 29 (3) US business will have access to an affordable, high-performance CZT/CdTe material that can be 30 obtained for imaging instrumentation and other radiation detection applications.
