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  • 1
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    Interface markings in crystals experiment MA-060 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Doped germanium single crystals with interface demarcation were successfully grown during the Apollo Soyuz Test Project mission. Interface demarcation permitted the determination of the microscopic growth behavior from the onset to the termination of solidification. Preliminary segregation analysis shows striking differences in segregation in the presence of gravity. The correlation between microscopic growth rate behavior and the composition of the solid on the microscale is being evaluated.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA. Lyndon B. Johnson Space Center Apollo-Soyuz Test Project; 8 p
    Format: text
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  • 2
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    New outlook on control of crystalline and chemical perfection during growth of silicon (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Significant progress has been made in our understanding of the Czochralski crystal growth process with the realization that the incorporation of oxygen into silicon is directly related to the internal gettering capability of wafers during device fabrication. It was also recognized that the electronic properties exhibited by silicon during various stages of device fabrication were significantly affected by the thermal history of the silicon during the post-growth cool-down period. Turbulent melt convection, induced by unavoidable destabilizing thermal gradients, was found to interfere with homogeneous dopant (and oxygen) incorporation and to influence markedly the dynamics of nonequilibrium point defects in the solidified silicon matrix during the cool-down period. In view of the unavoidability of destabilizing thermal gradients in conventional crystal growth configurations, melt stabilization through the application of magnetic fields is generally considered a viable approach. Control of heat input to the melt through heat pipe systems, as used during growth of germanium, cannot be applied to industrial growth of silicon. Recent studies have shown that heat exchange systems located coaxially about a growing crystal can be used to stabilize and control not only heat transfer in the grown crystal, but also in the melt adjacent to the solidification interface.
    Keywords: SOLID-STATE PHYSICS
    Type: JPL Proceedings of the Flat-Plate Solar Array Project Workshop; p 83-96
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  • 3
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    Heat flow control and segregation in directional solidification (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Optimization of the vertical Bridgman technique for growth of electronic materials in single crystal form was investigated. The limitations of the crystal growth configuration were experimentally determined and heat transfer related deficiencies identified. Design of an alternate system was based on the use of heat pipes separated by a gradient region. Heat transfer analyses based on one and two dimensional models indicated the necessity of a flexible gradient zone configuration. Directional melting of binary systems as encountered during seeding in melt growth was analysed for concurrent compositional changes at the crystal-metal interface, and the theoretical treatment numerically applied to HgCdTe and Ga doped germanium. A theoretical and experimental study of the thermal effects associated with current flow was conducted. It was found that experimental measurements of dc induced growth during crystal pulling can be used for the precise determination of the Peltier coefficient.
    Keywords: SOLID-STATE PHYSICS
    Type: The Mater. Process. Res. Base of Mater. Process. Center; p 123-154
    Format: text
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  • 4
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    Growth rate dependence of the interface distribution coefficient in the system Ge-Ga (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Crystal Growth (ISSN 0022-0248); 60; 1982
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  • 5
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    Heat transfer analysis of the Bridgman-Stockbarger configuration for crystal growth. Part 1: Analytical treatment of the axial temperature distribution (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: All first order effects on the axial temperature distribution in a solidifying charge in a Bridgman-Stockbarger configuration for crystal growth are analyzed on the basis of a one dimensional model whose validity can be verified through comparison with published finite difference ana;uses of two dimensional models. The model presented includes an insulated region between axially aligned heat pipes and considers the effects of charge diameter, charge motion, thickness, and thermal conductivity of a confining crucible, thermal conductivity change at the crystal-melt interface, generation of latent heat at the interface, and finite charge length. Results are primarily given in analytical form and can be used without recourse to computer work for both improve furnace design and optimization of growth conditions in a given thermal configuration.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-CR-116907 , NAS 1.26:169079
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  • 6
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    Segregation during directional melting and its implications on seeded crystal growth: A theoretical analysis (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Directional melting of binary systems, as encountered during seeding in melt growth, is analyzed for concurrent compositional changes at the crystal-melt interface. It is shown that steady state conditions cannot normally be reached during seeding and that the growth interface temperature at the initial stages of seeded growth is a function of backmelt conditions. The theoretical treatment is numerically applied to Hg1-xCdXTe and Ga-doped Ge.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-CR-169072 , NAS 1.26:169072
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  • 7
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    Segregation effects during growth of pseudo-binary system with large liquidus-solidus separation (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Results are reported for an experimental study of the seeded growth, of PbSnTe single crystals in a vertical Bridgman-Stockbarger (B-S) furnace. Profiles of axial and radial segregation of Sn are presented for crystal growth from melts with aspect ratios of 15 and 6.8; the profiles indicate intense convective mixing. A one-dimensional model of heat and mass transfer in an idealized B-S furnace with diffusion control is used to examine the importance of liquidus-solidus separation in determining growth-rate and composition transients in a pseudobinary system. It is shown that the coupling of heat and mass transfer in a pseudobinary system with a large liquidus-solidus separation causes the transient behavior in a nondilute system to differ markedly from such behavior in a dilute system and that PbSnTe crystals with a reasonable diameter can be grown under nearly convectionless conditions in a microgravity environment.
    Keywords: SOLID-STATE PHYSICS
    Type: IAF PAPER 82-130
    Format: text
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  • 8
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    Quantitative determination of zero-gravity effects on electronic materials processing germanium crystal growth with simultaneous interface demarcation experiment MA-060, section 5 (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero g conditions were investigated. The germanium (doped with gallium) system was selected because it was extensively studied on Earth and because it lends itself to a very detailed macroscopic and microscopic characterization. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. On the basis of the results obtained to date, there is no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-CR-161964
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  • 9
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    Seeded crystal growth of pseudobinary systems with large liquidus-solidus separation (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The design and execution of seeded melt growth involving concentrated alloys is strongly dependent on the crystal-melt interface temperature and its change during seeding and growth. Thermodynamic instabilities during the seeding process can be controlled by the choice of the seed and melt composition and by the axial temperature gradient of the growth apparatus. These basic factors controlling seeded melt growth of concentrated alloys are of major importance for planning space experiments.
    Keywords: SOLID-STATE PHYSICS
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  • 10
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    Characterization of convection related defects in II-VI compound semiconductors (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The research carried out under NAG8-913, 'Characterization of Convection Related Defects in II-VI Compound Semiconductors', was aimed at exploration of the potential of axial magnetic fields for melt stabilization when applied in Bridgman geometry to the growth of HgMnTe. The thrust of the work was directed at the experimental establishment of the limits of magnetic melt stabilization during crystal growth and at the analytical verification of the effects of stabilization on critical materials properties. The data obtained indicate noticeable stabilization effects, particularly as far as the formation of microscopic compositional inhomogeneities is concerned. The effects of magnetic fields on precipitate formation are found to be minor. Magnetic field effects were investigated for both 'Bridgman' and 'travelling heater' geometries. The research was conducted during the period from May 22 to September 30, 1992.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA-CR-194704 , NAS 1.26:194704
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