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Modeling the Migration of Tellurium-Rich, Second-Phase Particles in Cadmium Zinc Telluride (CZT) via Temperature Gradient Zone Melting (TGZM)

Kerry Wang ,  Andrew Yeckel ,  Jeffrey J. Derby 

University of Minnesota, Chemical Engineering and Materials Science, 421 Washington Ave. S.E., Minneapolis, MN 55455, United States

Abstract

Crystals of cadmium zinc telluride (CZT) typically exhibit significant populations of large (10 micron and above) tellurium-rich particles that are deleterious to the performance of semiconductor radiation detectors.  While it is well understood that melt growth of CZT can produce crystalline material that is supersaturated with tellurium, providing a thermodynamic basis for the existence of these second-phase particles, their formation mechanisms are not well understood.  

As an alternative to preventing particle formation during the growth process (which may not be possible), an interesting post-growth treatment may provide a means to higher-quality crystals.  Namely, these large, tellurium-enriched, secondary-phase particles can be induced to move away from a region of grown crystal and accumulate elsewhere, leaving higher-quality regions that contain far fewer particles. This accomplished by heating the sample to slightly above the eutectic temperature (the melting point of the second-phase particles) and engineering a temperature gradient across the sample. Under such conditions, the now-liquid particle dissolves on the hot side and re-solidifies on the cool side, with a net effect of migrating toward the hotter region.  This process is termed “temperature gradient zone melting,” or TGZM.

We will present the formulation and implementation of steady-state and dynamic models that employ the Galerkin finite element method and elliptic mesh generation techniques to solve for particle migration via TGZM.  Such an approach is particularly well suited for rigorous and accurate representation of geometrical and interfacial interactions in this system.  We will also present initial results to verify the model and identify the dominant physical interactions involved in this process.  We will also compare preliminary model results with data currently being taken on TGZM applied to CZT crystals in experiments at Brookhaven National Laboratories conducted by collaborators at Alabama A&M University.

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Supported in part by U.S. Department of Homeland Security, 2012-DN-077-ARI066-02, the content which does not necessarily reflect the position or policy of the United States Government, and no official endorsement should be inferred.

 

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Related papers

Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 4, by Jeffrey J. Derby
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-27 18:16
Revised:   2013-03-27 18:16