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  • 1
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    In:  CASI
    Publication Date: 2006-07-02
    Description: The preparation of building flight hardware and carrying out experiments in space was investigated. The ground based investigation phase A/B of the experimental float zoning of silicon is outlined. The overall program goals, leading to recommending experiments to be done in phase C/D are spelled out. Thermophysical properties which must be accurately known to compare thermophysical models to experimental zoning of silicon are listed.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: Float Zone Workshop; p 111-124
    Format: text
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  • 2
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    In:  CASI
    Publication Date: 2006-07-02
    Description: The need for power to grow silicon of a size suitable to make into devices is addressed. The expected results are tied to available power. The projection of the size of float zone crystals as a function of time is discussed. An accompanying graph shows that 4 in. will be the normally used diameter by 1985 and 5 in. by 1990. Material to be tested in device lines in this time frame should be 4 in. or more. The various power losses, 25 kW with a 50% power efficiency, which is much improved over present RF heating efficiencies.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: Float Zone Workshop; p 83-88
    Format: text
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  • 3
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    In:  CASI
    Publication Date: 2006-07-02
    Description: Payoffs of crystal growth in space in the areas of understanding growth and melt flow mechanisms, the growth of more uniform crystals with fewer defects, and the growth of crystals difficult or impossible to grow on Earth are summarized. The advantages of various heating methods are summarized. Critical devices requiring the uniformity and lower defect density of crystals grown in space are listed.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: Float Zone Workshop; p 23-33
    Format: text
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  • 4
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    In:  CASI
    Publication Date: 2006-07-02
    Description: The purposes of the float zone working group are summarized. Present and proposed U.S. and European research programs are listed, and power needs for float zoning surveyed. A 1981 to 1991 schedule for development efforts is presented.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: Float Zone Workshop; p 1-10
    Format: text
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  • 5
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: An overview of the state of the art of processing silicon for use as infrared detectors is presented. Improvements in the process that could be obtained in a low-g environment were examined. The various requirements for the different types of Si detector materials are summarized.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA. Marshall Space Flight Center Float Zone Workshop; p 57-72
    Format: text
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  • 6
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    In:  CASI
    Publication Date: 2019-06-28
    Description: This research program is directed toward the understanding of the float zone crystal growth process, the melt interactions which lead to crystal inhomogeneities, and the influence of microgravity on reducing these inhomogeneities. Silicon was selected as the model crystal because its inhomogeneities lead to known variations in device performance, and because the mechanisms involved in its growth are understood better than for other high temperature crystals. The objective of the program is to understand the growth mechanisms in float zone growth and thereby determine the feasibility and advantages of float zone growth of silicon under microgravity conditions. This will be done by characterizing the growth at g = 1, projecting the changes in melt flows due to microgravity, observing these in space growth and determining the effects on defective inhomogeneities. A Thin Rod Zoner was constructed as a laboratory prototype for flight growth of 5 mm diameter silicon crystals, which can be done within the power and cooling capabilities of shuttle flights. A new method of zoning silicon, using resistance heating, has resulted in melting 5 mm diameter ingots.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA, Washington Microgravity Sci. and Appl. Program Tasks; p 20
    Format: text
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  • 7
    Publication Date: 2019-06-28
    Description: A breadboard float zone experimental system has been established at Westech Systems for use by NASA in the float zone experimental area. A used zoner of suitable size and flexibility was acquired and installed with the necessary utilities. Repairs, alignments and modifications were made to provide for dislocation free zoning of silicon. The zoner is capable of studying process parameters used in growing silicon in gravity and is flexible to allow trying of new features that will test concepts of zoning in microgravity. Characterizing the state of the art molten zones of a growing silicon crystal will establish the data base against which improvements of zoning in gravity or growing in microgravity can be compared. 25 mm diameter was chosen as the reference size, since growth in microgravity will be at that diameter or smaller for about the next 6 years. Dislocation free crystals were growtn in the 100 and 111 orientations, using a wide set of growth conditions. The zone shape at one set of conditions was measured, by simultaneously aluminum doping and freezing the zone, lengthwise slabbing and delineating by etching. The whole set of crystals, grown under various conditions, were slabbed, polished and striation etched, revealing the growth interface shape and the periodic and aperiodic natures of the striations.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-170668 , NAS 1.26:170668 , JA64
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  • 8
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    In:  CASI
    Publication Date: 2019-06-28
    Description: Presentations made on space based float zone crystal growth and melt behavior are summarized and handouts illustrating the presentations are presented.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CP-2226 , NAS 1.55:2226
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  • 9
    Publication Date: 2019-07-13
    Description: A resistance heated zoner, suitable for early zoning experiments with silicon, was designed and put into operation. The initial power usage and size was designed for an shown to be compatible with payload carriers contemplated for the Shuttle. This equipment will be used in the definition and development of flight experiments and apparatus for float zoning silicon and other materials in microgravity.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-170919 , NAS 1.26:170919
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  • 10
    Publication Date: 2019-07-13
    Description: The flow instabilities in floating zones of silicon were investigated and methods for investigation of these instabilities in microgravity were defined. Three principal tasks were involved: (1) characterization of the float zone in small diameter rods; (2) investigation of melt flow instabilities in circular melts in silicon disks; and (3) the development of a prototype of an apparatus that could be used in near term space experiments to investigate flow instabilities in a molten zone. It is shown that in a resistance heated zoner with 4 to 7 mm diameter silicon rods that the critical Marangoni number is about 1480 compared to a predicted value of 14 indicative that viable space experiments might be performed. The prototype float zone apparatus is built and specifications are prepared for a flight zoner should a decision be reached to proceed with a space flight experimental investigation.
    Keywords: ASTRONAUTICS (GENERAL)
    Type: NASA-CR-171531 , NAS 1.26:171531
    Format: application/pdf
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