17 September 2009 Characterization of secondary phases in modified vertical Bridgman growth CZT
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Abstract
CdZnTe or "CZT" crystals are highly suitable for use as a room temperature based spectrometer for the detection and characterization of gamma radiation. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. For example, various structural heterogeneities within the CZT crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SP) can have a negative impact on the detector performance. In this study, a CZT material was grown by the modified vertical Bridgman growth (MVB) method with zone leveled growth without excess Te in the melt. Visual observations of material from the growth of this material revealed significant voids and SP. Samples from this material were analyzed using various analytical techniques to evaluate its electrical properties, purity and detector performance as radiation spectrometers and to determine the morphology, dimension and elemental /structural composition of one of the SP in this material. This material was found to have a high resistivity but poor radiation spectrometer performance. It had SP that were rich in polycrystalline aluminum oxide (Al2O3), metallic Te and polycrystalline CdZnTe and 15 to 50 μm in diameter. Bulk elemental analyses of sister material from elsewhere in the boule did not contain high levels of Al so there is considerable elemental impurity heterogeneity within the boule from this growth.
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Martine C. Duff, Martine C. Duff, Kelvin G. Lynn, Kelvin G. Lynn, Kelly Jones, Kelly Jones, Zurong R. Dai, Zurong R. Dai, John P. Bradley, John P. Bradley, Nick Teslich, Nick Teslich, } "Characterization of secondary phases in modified vertical Bridgman growth CZT", Proc. SPIE 7449, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XI, 74490N (17 September 2009); doi: 10.1117/12.829290; https://doi.org/10.1117/12.829290
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