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The preparation from vapor and the structure of filamentary crystals of silicon have been studied in detail. It was found by chemical etching, by examination for a twist associated with a screw dislocation, and by observations in the electron microscope, that both ribbons and needles of small dimensions are free of dislocations and imperfections. Certain impurities such as gold, nickel, or platinum, however, are essential for the growth of filamentary crystals. The growth of micron size and larger whisker crystals from the vapor takes place in two stages. The first is a rapid extension in length of a leader-like crystal of small cross section; the second, a slow thickening of the leader through deposition on lateral faces. Initial growth is associated with impurities and does not require an axial screw dislocation. Subsequent growth may be explained by classical nucleation at a step and lateral translation of the step.

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GaAs and GaP whisker crystals have been grown by the vapor—liquid—solid mechanism of crystal growth. Gold, palladium, platinum, and gallium have been used to produce the required liquid layer. The system employing wet hydrogen developed by Frosch and Thurmond was used for most of the crystal growing. p- and n-type crystals were produced. GaAs crystals were found to have three morphologies: a twinned ribbon with a 〈112〉 growth direction and {111}, {110}, and {113} lateral faces; a single-crystal hexagonal needle with a 〈111〉 growth direction and {110} lateral faces; and a newly found habit, a single-crystal blade which grows in an 〈001〉 direction with {110} lateral faces. The largest GaAs blades were about 8×0.3 ×0.010 mm and grew at a rate of about 1 mm/h. The twinned ribbon and the 〈001〉, {110} morphologies were found in GaP.

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