Crystal Growth Processes and Advanced Materials Manufacture

Professor Jeffrey Derby and his research group from the Department of Chemical Engineering and Materials Science are applying large-scale numerical simulation and high-performance computing to the study of engineering processes used in the manufacture of advanced materials. Four primary areas of study are the growth of large single crystals, ceramic sintering, microwave heating, and resin transfer molding processes. This article highlights their work on large single crystals which are used in electrical and optical devices, solid state lasers, infrared detectors and other devices with a wide range of medical and industrial applications. One such crystal is cadmium zinc telluride, an important bulk material for infrared detectors. Derby is working on a project with Johnson Matthey Electronics Inc., of Spokane, Washington to speed up the crystal growth process in order to produce high-grade crystals more efficiently, thereby making it economically feasible for cadmium zinc telluride crystals to be used in commercial applications. A similar project with Lawrence Livermore National Laboratories involving the production of potassium dihydrogen phosphate (KDP) crystals is also underway.

In one process, known as the Czochralski method, growth is achieved from a seed crystal simultaneously pulled and rotated above a melt. This process produces good results, but the dynamics involved are poorly understood. In an effort to better understand the dynamics of this process, three- dimensional, time-dependent calculations of flows done on the Thinking Machines Corportation CM-5 were performed by the Derby group. They show a transition from a steady, axisymmetric flow to a time-dependent, three-dimensional state characterized by an annular wave structure which strongly affects the temperature distribution and heat transfer through the melt. These findings are buttressed by the fact that they correspond well to experimental results from a benchmark system of baroclinic annular waves used by atmospheric scientists.

Additional crystal growth research focuses on reducing the impact of impurities in the melt and resulting crystal. This includes modeling of vortical flows behind the leading edges of crystals in a moving melt, and analysis of the Bridgman system by calculating the effects of tilting on contaminants and their distribution in the melt.

Professor Derby's work aims to increase our understanding of materials processing systems as a crucial first step in streamlining advanced materials production. For a more detailed discussion of this and related research please consult the following University of Minnesota Supercomputer Institute preprint series numbers. They are available by sending email to: kilber@msi.umn.edu

• UMSI 94/180 September 1994
  Three-Dimensional Melt Flows in Czochralski Oxide Growth: High-Resolution, Massively Parallel, Finite Element Computations
  Qiang Xiao and Jeffrey J. Derby

• UMSI 94/205 November 1994
  Modeling Heat Transfer and Segregation During the Vertical Bridgman Growth of Cadmium Zinc Telluride
  Satheesh Kuppurao, Jeffrey J. Derby, and Simon Brandon

• UMSI 95/10 January 1995
  Macroscopic Transport Processes During the Growth of Single Crystals from the Melt
  Jeffrey J. Derby

• UMSI 95/11 January 1995
  Large-Scale Numerical Modeling of Bulk Crystal Growth from the Melt and Solution
  Jeffrey J. Derby, Satheesh Kuppurao, Qiang Xiao, A. Yeckel, and Y. Zhou

• UMSI 95/41 March 1995
  Parallel Computation of Radiation View Factors Between Two Arbitrarily Oriented Surfaces
  Satheesh Kuppurao, Iwan Tantra, and Jeffrey J. Derby