Crystal Growth from the Vapour Phase

Kaldis, E.; Cadoret, R.; Schönherr, E.

doi:10.1007/978-3-642-46613-7_11

Cited by 6 publications

(5 citation statements)

References 28 publications

(66 reference statements)

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“…[10][11][12] Effective performance optimization at this point depends on an understanding of the specific chemical and structural origins of the improvement that has been achieved and association of the desired crystal regularity with individual growth parameters, in microgravity 13 as well as on the ground. 14 Therefore, we have examined residual crystalline irregularities associated with various crystal growth conditions, their origins, their relationship to growth parameters, and the influence of each on electronic performance.…”

Section: A Motivationmentioning

confidence: 99%

Enhancement of mercuric iodide detector performance through increases in wafer uniformity by purification and crystal growth in microgravity

Steiner

Laor

1999

Journal of Applied Physics

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Wafers from mercuric iodide crystals grown in microgravity on two occasions have previously been found to be characterized by a higher hole mobility-lifetime product, which enables energy dispersive radiation detectors with superior resolution. In the present work, we have identified the specific structural modifications that are responsible for this enhanced performance. As a result of this study, the performance of terrestrial wafers also has been improved but not yet to the level of wafers grown in microgravity. High resolution synchrotron x-ray diffraction images of a series of wafers, including those grown both in microgravity and on the ground, reveal two principal types of structural changes that are interrelated. One of these, arrays of inclusions, affects performance far more strongly than the other, variation in lattice orientation. Inclusions can be formed either from residual impurities or in response to deviations from ideal stoichiometry. The formation of both types is facilitated by gravity-driven convection during growth. As the level of inclusions is reduced, through growth from material of higher purity, through the achievement of balanced stoichiometry, or by suppression of convection mixing during crystal growth, the hole mobility-lifetime product is enhanced in spite of an accompanying decreased uniformity in lattice orientation. Sixfold enhancement in the performance of x-and ␥-ray detectors has been accomplished to date. Further augmentation in performance appears likely.

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Section: A Motivationmentioning

confidence: 99%

Enhancement of mercuric iodide detector performance through increases in wafer uniformity by purification and crystal growth in microgravity

Steiner

Laor

1999

Journal of Applied Physics

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“…These impurities would be incorporated into the growing crystal in a non-uniform way mainly because of the fluid-dynamic interplay between diffusion and free convection. This effect, quite obvious when the overall pressure is high (i.e., at large Grashof numbers), should also occur at small Grashof numbers, as previously advanced for the PVT growth of mercury iodide [4].…”

Section: Introductionmentioning

confidence: 87%

“…Henceforth, the crystallization heat has usually time enough to dissipate even when the thermal conductivity of the crystal is very low. Possible heat-transfer limitations have been suggested when large-size crystals are grown ( case of mercury iodide [4] ) or when the growth rate is sufficiently high as in effusive growth cells. The surface rounding of HMT crystals, occasionally observed in SOPVT growth processes [1], might very likely be due to these limitations, especially if the presence of impurities favours an increasing roughening level of the growing interface [12].…”

Section: Closing Remarksmentioning

confidence: 99%

Progressive growth rate reduction due to impurity desorption in vapor grown hexamethylenetetramine crystals

Paorici

Zha²,

Razzetti

et al. 2005

Cryst. Res. Technol.

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The authors report on measurements of the growth rate of hexamethylenetetramine ( HMT ) crystalline layers, when grown by physical vapor transport ( PVT ) in closed ampoules. The measurements are done in-situ by making use of a telemetric system, by which, at regular time intervals, photographs of the source material volume are taken as is being reduced because of mass transfer. After storing the photographs, in real time, in a pc, a suitable software allows to calculate the mass transport rate during growth. A regular and consistent decrease of the growth rate, as time increases, is always observed in the various growth runs, each of which being carried out for about 80 hours at a source temperature of 94 °C under 1 °C undercooling. Similar decreases have been previously reported for other materials and variously explained. In our case, the growth rate decrease is explained on the basis of a uni-dimensional PVT model as mainly due to the desorption of volatile impurities which introduce diffusional barriers to the vapour mass transport in a very-low pressure ( less than 1 mbar ) PVT system.

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“…Comprehensive reviews pertinent to the fundamental techniques of VCG are available in many articles, for example, Kaldis (1974), Faktor and Garrett (1974), Kaldis et al (1987). Comprehensive reviews pertinent to the fundamental techniques of VCG are available in many articles, for example, Kaldis (1974), Faktor and Garrett (1974), Kaldis et al (1987).…”

Section: Vapor Crystal Growth (Vcg)mentioning

confidence: 99%

“…Kaldis (1987) reviewed three low-temperature growth experiments performed in space. This process is employed in growing sizable crystals of many materials, such as various chalcogenicles (e.g., many semiconductors of the groups II-VI and IV-VI), halides (e.g., alkali halides, CaF2, MgF2, CuBr), a few metals, oxides and carbides.…”

Section: Pvt Processmentioning

confidence: 99%

Microgravity

Yang

1994

Transport Phenomena in Manufacturing and Materials Processing

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Crystal Growth from the Vapour Phase

Cited by 6 publications

References 28 publications

Enhancement of mercuric iodide detector performance through increases in wafer uniformity by purification and crystal growth in microgravity

Enhancement of mercuric iodide detector performance through increases in wafer uniformity by purification and crystal growth in microgravity

Progressive growth rate reduction due to impurity desorption in vapor grown hexamethylenetetramine crystals

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