US3632405A - Crystals, in particular crystal whiskers and objects comprising such crystals - Google Patents

Crystals, in particular crystal whiskers and objects comprising such crystals Download PDF

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Publication number
US3632405A
US3632405A US815678A US3632405DA US3632405A US 3632405 A US3632405 A US 3632405A US 815678 A US815678 A US 815678A US 3632405D A US3632405D A US 3632405DA US 3632405 A US3632405 A US 3632405A
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Prior art keywords
metal
crystals
crystallization
partial pressure
temporarily
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US815678A
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English (en)
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Wilhelmus Franclsc Knippenberg
Gerrit Verspul
Johan Charles Marie Basart
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US Philips Corp
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US Philips Corp
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/04—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt
    • C30B11/08—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method adding crystallising materials or reactants forming it in situ to the melt every component of the crystal composition being added during the crystallisation
    • C30B11/12—Vaporous components, e.g. vapour-liquid-solid-growth
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

Definitions

  • Trifari ABSTRACT A method of manufacturing filamentary crystals, i.e., whiskers, and controlling the growth thereof in which a substrate on which are provided particles of a metal powder is heated so that the metal particles melt and fonn molten droplets while an atmosphere containing the substance forming the crystals is passed over the substrate. The substrate is dissolved in the metal droplets and precipitates growing a filament of whisker epitaxially. The thickness of the crystal is then controlled by adjusting the partial pressure of the metal in the atmosphere which controls the size of the droplets. In some cases, a separate source of metal for controlling the partial pressure of the metal in the atmosphere is provided.
  • the invention relates to the manufacture of crystals in which the crystal growth takes place by a VLS-mechanism.
  • the invention relates in particular to the manufacture in this manner of thin filamentary crystals, sometimes referred to as whiskers, which are to be understood to mean herein elongate crystals independently of the shape of their transverse cross section.
  • the invention moreover relates to crystals thus manufactured and to objects comprising such crystals.
  • Crystal growth by a VLS-mechanism (Vapour-Liquid- Solid) is described in Transactions of the Metallurgical Society of the AIME” 233 (I965), 1053 et seq.
  • the substance to be crystallized or its components are taken up from a gaseous phase by droplets provided locally on a substrate and consisting of a metal in which the substance to be crystallized is soluble, the substance being deposited on the substrate by the intermediation of the said droplets.
  • the crystal growth is strongly anisotropic and actually it takes place substantially only at right angles to the surface of the substrate. This is a result of the circumstance that the absorption of the substance to be crystallized or its components from the gaseous phase occurs preferentially at the free surface of the liquid metal phase, whereas the deposition takes place at the droplet-substrate-interface only.
  • the shape of the resulting crystal is slightly conical mainly as a result of the decrease of the volume of the metaldroplets due to evaporation, particularly in the case of prolonged growth. Other factors also may possibly stimulate said conical growth, for example, as stated on page 1059 of the abovementioned paper, a laminated growth on the side faces of the crystal. Moreover the evaporation of metal has for its result that the longitudinal growth of the crystals is limited.
  • One of the objects of the invention in VLS-growth is to control the thickness of the crystals and/or to obviate said limitation in longitudinal growth.
  • the invention relates to a method of manufacturing crystals, particularly filamentary crystals, such as whiskers, in which crystal growth takes place by a VLS-mechanism, which is characterized in that the thickness of the crystals during the growth is controlled by controlling the size of the droplets of the metal which in the VLS-growth serves as the liquid phase.
  • the influence of the factors which may cause thickness variations during the crystal growth can be completely compensated for by adjusting the size of the metal droplets by means of adjusting the above partial pressure so that crystals with a constant thickness are obtained.
  • crystals with a previously determined variation in thickness can be obtained by varying the size of the droplets continuously or discontinuously during the growth by varying the said partial pressure.
  • restriction in the longitudinal growth due to disappearance of the metal can be avoided.
  • the crystallization atmosphere is put into contact with a source of the metal or the metal compound, the partial metal pressure in the crystallization space being adjusted by the temperature to which said source is exposed.
  • this gas may be used as a transport medium for the metal and the compound, respectively, and the amount of metal supply or drain, may be controlled by means of the flow rate of the gas.
  • For temporarily reducing the droplets forced removal of metal may be obtained by temporarily reducing the gas pressure and/or temporarily lowering the temperature of a metal source if present.
  • temporarily the gas being conducted through the crystallization space may be given a content of the metal or the metal compound which is lower than that in the crystallization atmosphere or may be entirely free from them.
  • a substance is added to the gas current which reacts with the metal while forming a volatile. compound so that metal of the droplets is carried away with the gas.
  • a favorable condition in supplying and removing metal via the gaseous phase for adjusting the droplet size is that this occurs preferentially at the liquid metal surface, similar to the absorption from the gaseous phase of the substance to be crystallized and its components, respectively.
  • any metal deposition on the side faces of the crystals occurs a favorable use of this deposition may be made in the case these crystals are destined in the form of whiskers, to reinforce materials which do not or poorly wet the crystals as such.
  • whiskers of silicon carbide which are not wetted by most of the metals and alloys but in the presence of an adhering metal deposition also show a more effective adhesion to metals, in which they are incorporated by introducing them into a melt of such a metal for improving the mechanical properties.
  • the metal deposition on the crystals may be promoted, if required, by strongly increasing for a short period of time the partial pressure of the metal vapor prior to terminating the crystal growth.
  • undesired metal deposition may be removed by grinding or etching.
  • the crystals obtained according to the invention are of advantage for various uses in technology.
  • whiskerlike crystals with discontinuously varying thicknesses may be of advantage for reinforcing materials, because the presence of thickened portions ensure that the crystals are satisfactorily moved mechanically in the material.
  • the conductivity properties thereof may be adjusted, as is known, by incorporating dopes. As is likewise known, these additions may be incorporated in the crystals during their growth via the gaseous phase or in an aftertreatment by diffusion.
  • reference number 1 denotes a graphite crucible, 60 mm. high, 45 mm. inside diameter, 53 mm. outside diameter.
  • 3 gm. of silicon dioxide 2 are provided in the crucible in which a graphite tray 3 was placed.
  • the assembly was placed in a quartz tube (not shown) in which a hydrogen. atmosphere was maintained of approximately atmospheric pressure.
  • an inductance coil (not shown) is provided for heating the graphite crucible.
  • a silicon and carbon containing hydrogen atmosphere was built up in the crucible.
  • the iron grains 5 silicon and carbon were takenvup herefrom, the grains. melting and silicon carbide growing from the resulting liquid phase according to a VLS-mechanism-epitaxially onto the silicon carbide lid 4, serving as a substrate.
  • One of the formed crystals had a thickness of 24 pm. at its base which, after agrowth of 1 mm., had reduced at its growing end to 19pm. and, upon further growth over mm., had reduced at its growing end to [6.5 pm. in a period of time of 19 hours. In the same period, another crystal had grown over a length of 1 mm., the thickness having reduced from 34 m. at its base to 29pm. at its growing end.
  • the partial iron pressure was increased so that the iron droplets even increase in size and the formed crystals become gradually thicker in the direction of growth.
  • the thickness of a crystal which had a base of 8.45am. had increased in thickness at its growing end to 9pm. after a growth of 3 mm. and to 10.81am. after a further growth of 0.7 mm.
  • EXAMPLE ll As shown in FIG. 2 a graphite crucible 7 containing quartz grains 8 was provided in a graphite boat 6. Above the crucible 7 a plate 9 of sublimated silicon carbide of 20 mm. diameter was arranged. On the side of the plate 9 facing the crucible 7, iron grains 10 smaller than Spurn. were provided. Furthermore a quartz tray 11 containing 1 gm. of iron powder 12 was placed in the graphite boat 6.
  • the assembly was arranged in a tube of sintered aluminum oxide (not shown) which was surrounded by a tubular electric furnace (not shown).
  • silicon carbide crystals having substantially constant thicknesses throughout their lengths grew on the plate 9. For example, over a length of a few centimeters and a thickness of about l0 am, no or only slight variations in thickness were found such as just a local deviation of approximately 0.5 pm.
  • EXAMPLE Ill As shown in FIG. 3, an aluminum oxide tray 14 containing 0.5 gm. of gold 15 was placed in a boat of sintered aluminum oxide 13. A disk of silicon 16, mm. diameter, containing at its lower side gold grains 17 of approximately 10pm. was provided on the boat 13.
  • the assembly was arranged in an aluminum oxide tube, (not shown) which was surrounded by a tubular electric furnace.
  • whiskers were obtained the thickness of which locally dropped considerably.
  • a method of manufacturing filamentary of constant thickness crystals comprising the steps of exposing a substrate having thereon metal particles to a gaseous atmosphere containing both the material to be deposited in crystalline form on the substrate and vapors of said metal particles heating the substrate to a temperature at which the metal particles become molten and form metal droplets which dissolve the material to be deposited therein which precipitates on the substrate and forms filamentary crystals, and controlling the thickness of the deposited crystals by adjusting the partial pressure of the metal in said atmosphere.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Inorganic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US815678A 1968-04-13 1969-04-14 Crystals, in particular crystal whiskers and objects comprising such crystals Expired - Lifetime US3632405A (en)

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NL6805300A NL6805300A (en)) 1968-04-13 1968-04-13

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BE (1) BE731440A (en))
CH (1) CH538300A (en))
DE (1) DE1917136C3 (en))
ES (1) ES365930A1 (en))
FR (1) FR2006185A1 (en))
GB (1) GB1229900A (en))
NL (1) NL6805300A (en))
NO (1) NO124059B (en))

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5381753A (en) * 1992-04-30 1995-01-17 Matsushita Electric Industrial Co., Ltd. Fabrication method of fine structures
US5404836A (en) * 1989-02-03 1995-04-11 Milewski; John V. Method and apparatus for continuous controlled production of single crystal whiskers
US6221154B1 (en) * 1999-02-18 2001-04-24 City University Of Hong Kong Method for growing beta-silicon carbide nanorods, and preparation of patterned field-emitters by chemical vapor depositon (CVD)
US6451113B1 (en) * 1996-04-01 2002-09-17 Evgeny Invievich Givargizov Method and apparatus for growing oriented whisker arrays
US20020172820A1 (en) * 2001-03-30 2002-11-21 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3346414A (en) * 1964-01-28 1967-10-10 Bell Telephone Labor Inc Vapor-liquid-solid crystal growth technique
US3493431A (en) * 1966-11-25 1970-02-03 Bell Telephone Labor Inc Vapor-liquid-solid crystal growth technique

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3346414A (en) * 1964-01-28 1967-10-10 Bell Telephone Labor Inc Vapor-liquid-solid crystal growth technique
US3493431A (en) * 1966-11-25 1970-02-03 Bell Telephone Labor Inc Vapor-liquid-solid crystal growth technique

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5404836A (en) * 1989-02-03 1995-04-11 Milewski; John V. Method and apparatus for continuous controlled production of single crystal whiskers
US5381753A (en) * 1992-04-30 1995-01-17 Matsushita Electric Industrial Co., Ltd. Fabrication method of fine structures
US6451113B1 (en) * 1996-04-01 2002-09-17 Evgeny Invievich Givargizov Method and apparatus for growing oriented whisker arrays
US6221154B1 (en) * 1999-02-18 2001-04-24 City University Of Hong Kong Method for growing beta-silicon carbide nanorods, and preparation of patterned field-emitters by chemical vapor depositon (CVD)
US20050161662A1 (en) * 2001-03-30 2005-07-28 Arun Majumdar Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US6882051B2 (en) 2001-03-30 2005-04-19 The Regents Of The University Of California Nanowires, nanostructures and devices fabricated therefrom
US20020172820A1 (en) * 2001-03-30 2002-11-21 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US6996147B2 (en) 2001-03-30 2006-02-07 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US20070164270A1 (en) * 2001-03-30 2007-07-19 Arun Majumdar Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US7569847B2 (en) 2001-03-30 2009-08-04 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US7569941B2 (en) 2001-03-30 2009-08-04 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US20100003516A1 (en) * 2001-03-30 2010-01-07 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US7834264B2 (en) 2001-03-30 2010-11-16 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom
US9881999B2 (en) 2001-03-30 2018-01-30 The Regents Of The University Of California Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

Also Published As

Publication number Publication date
NL6805300A (en)) 1969-10-15
GB1229900A (en)) 1971-04-28
FR2006185A1 (en)) 1969-12-19
CH538300A (de) 1973-06-30
DE1917136C3 (de) 1974-05-16
DE1917136A1 (de) 1970-09-24
NO124059B (en)) 1972-02-28
ES365930A1 (es) 1971-03-16
DE1917136B2 (en)) 1973-10-04
BE731440A (en)) 1969-10-13

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