SBIR-STTR Award

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.

Public Health Relevance Statement:
Project Narrative The high spatial-resolution and energy-resolution of cadmium zinc telluride (CZT) and cadmium telluride (CdTe), compared to that of scintillators, offers superior image quality in nuclear medicine and X-ray imaging applications. Unfortunately, the current state-of-the-art (i.e. Traveler Heater Method) for growing CZT and CdTe crystals is slow, expensive, and does not meet the demands of the current market needs. The Accelerated Crucible Rotation Technique by Modified Vertical Bridgman (ACRT-MVB) is a new and rapid-production process for growing high-performance CZT and CdTe crystals, a process that will change the current CZT/CdTe market by providing affordable, high-quality devices to stakeholders in the high- demand and growing medical imaging markets.

Project Terms:
base; bone; Businesses; cadmium telluride; Caliber; CdZnTe; commercialization; cost; crystallinity; Crystallization; Densitometry; Dental; Detection; detector; Devices; Diagnostic Imaging; Diagnostic radiologic examination; Discipline of Nuclear Medicine; Fruit; Gamma Rays; Goals; Government; Grain; Growth; Harvest; High temperature of physical object; Hour; Image; improved; Industrialization; Industry; instrumentation; Medical; Medical Imaging; melting; Methods; National Security; new growth; oncology; Outcome; Performance; Phase; Positron-Emission Tomography; Price; Process; Production; Property; Radiation; radiation detector; Research; Resolution; Roentgen Rays; Rotation; scale up; Security; single photon emission computed tomography; Techniques; Technology; Temperature; Time; Travel; United States; Universities; Washington

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. CZT and CdTe remain the desired choice for room-temperature radiation detection, but it is 5 limited by high-cost and availability resulting from low yield and long production times associated with 6 commercial growth techniques, i.e. the Traveling Heater Method (THM). However, the application of the 7 Accelerated Crucible Rotation Technique (ACRT) growth method developed at WSU has proven to 8 produce industrial quality, high-performance CdTe/CZT. This recently developed growth method not only 9 allows CdTe/CZT to be grown with the same quality as material grown by THM, but also at growth rates10 approximately 10-20 times faster than THM. Specifically, CdTe/CZT is grown by THM at a rate of11 approximately 1-3 mm per day, whereas CdTe/CZT growth by ACRT can be accomplished at much faster12 rates of approximately 1-3 mm per hour. THM-grown CdTe/CZT requires a lower growth temperature for13 high-quality devices, which results in highly off-stoichiometric melts, thereby inducing the need for14 postprocessing. These major challenges associated with the crystal growth of CdTe/CZT have been15 overcome using ACRT. It is proposed here to further develop the ACRT growth process by introducing16 crystal seeding in the ACRT system for CdTe and scale this process to commercial-grade levels while17 continuing to improve the CdTe device properties for high-flux SPECT/CT applications. Chlorine doping18 will be further explored and optimized to achieve high resistivity and high mobility-lifetime CdTe devices.19 Numerous CdTe:Cl ingots will be grown, and devices will be produced from these ingots (cross strip and20 commercial pixel patterns). Devices will be sent to commercial partners and customers for validation in21 effort to integrate into commercial imaging systems. A prototype SPECT/CT system will be designed, built,22 and images will be collected. The medical/diagnostic imaging market is projected to cross $55.7 billion by23 2025. Stakeholders in the medical imaging market need CdTe/CZT devices now. The fruition of this project24 will be a significant reduction (>3x) of industrial-grade material costs by increasing the yield, reducing the25 growth time, and eliminating post-growth anneal treatments currently used by industry. With the fast-26 production time and high-performance of the CdTe/CZT produced in this effort, (1) the medical imaging27 market will finally have a fast turnaround time and consistent high-performance material that can easily be28 obtained, (2) a >3x price reduction is projected for CdTe/CZT, and (3) Stakeholders will have access to an29 affordable, high-performance CdTe/CZT material that can be obtained for imaging instrumentation and30 other radiation detection applications.

Public Health Relevance Statement:
Project Narrative The high spatial-resolution and energy-resolution of cadmium telluride (CdTe) and cadmium zinc telluride (CZT), compared to that of scintillators, offers superior image quality in nuclear medicine and X-ray imaging applications. Unfortunately, the current state-of-the-art (i.e. Traveler Heater Method) for growing CdTe/CZT crystals is slow, expensive, and does not meet the demands of the current market needs. The Accelerated Crucible Rotation Technique (ACRT) has recently been applied to CdTe/CZT and has proved to be rapid-production process for growing high-performance CdTe and CZT crystals, a process that will change the current CdTe/CZT market by providing affordable, high-quality devices to stakeholders in the high-demand and growing medical imaging markets.

Project Terms:
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