Electromagnetically-Stirred THM Process for Growth of CZT
Agency / Branch:
DOD / DTRA
OBJECTIVE: Improve radiation detection material processing for consistently more efficient larger detection materials with shorter overall preparation times. DESCRIPTION: The quality, quantity, size, and cost of radiation detection materials and system are limited by current manufacturing capabilities. Examples of current improvements have focused on hydrothermal process enhancement for cadmium zinc telluride (CZT) crystals and feedstock purification and conditioning. Next generation approaches to obtain cheaper higher quality detection materials incorporating nonhydrothermal processes and not solely dependent on feedstock material conditioning. Specific material quality and quantity metrics will be dramatically improved by these process innovations. Detection material characteristics must be maintained or exceeded. For example, consistent room temperature semiconductors with better than one percent energy resolution at 662 keV or scintillator materials with better than three percent. Processing methods should control, but not be based on standard material requirements such as ultra high purity and uniformity. Shortening the duration of material formation, as in the case of crystal growth while maintaining or improving detection performance are also essential. Post material formation reprocessing such as annealing and surface preparation are not considered. PHASE I: Examples of areas where dramatic improvements may be possible should be studied in the proof of concept phase to include: - Reduce crystal growth time from weeks to days and maintaining material quality - Increase usable detection material sizes in volume or usable area with no degradation in detector sensitivity - Improve detection material performance by nonhyrdothermal means (e.g., energy resolution) without increasing production cost - Improve chemical vapor deposition fabrication for radiation detector applications PHASE II: Prototype material fabrication must provide detection materials of sufficient size, quality and quantity for performance testing and be cost effective and production scalable. Methods and processes must be repeatable and reproducible. PHASE III DUAL USE APPLICATIONS: Scope of potential follow-on: - Engineering design and integration of prototype material fabrication process to improve existing radiation detection material processes - Extending prototype processing to other semiconductor or crystal growth material processing technology areas - Producing improved radiation detection materials and samples for special applications such as scientific and medical research in high energy physics and medical monitoring, and to allow for additional detection material characterization - Expanding production applications to solar cells and electronic component fabrication REFERENCES: 1. Chen, H. et al., "High-Performance, Large-Volume THM CdZnTe Detectors for Medical Imaging and Homeland Security Applications," Nuclear Science Symposium Conference Record, 2006. IEEE Volume 6, pp. 3629-3637. 2. Doering, R. (Ed.) et al., Handbook of Semiconductor Manufacturing Technology, CRC, 2007. 3. Hahto, S.K., "Negative ions for heavy ion fusion and semiconductor manufacturing applications," Review of Scientific Instrumentation (75, 1799), 2004. 4. Knoll, G.F., Radiation Detection and Measurement, John Wiley & Sons, 2000. 5. Levinshtein, M.E.(Ed.) et al., Properties of Advanced Semiconductor Materials: GaN, AIN, InN, BN, SiC, SiGe, John Wiley and Sons, 2001. 6. Richerson, D., Modern Ceramic Engineering: Properties, Processing, and Use in Design, CRC, 2005. 7. Schropp, R.E.I.et al.. "Hot wire CVD of heterogeneous and polycrystalline silicon semiconducting thin films for application in thin film transistors and solar cells" Materials Physics and Mechanics: pp. 73-82, 2000.
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