Vapor‐liquid‐solid mechanism of single crystal growth

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.

Study of the Filamentary Growth of Silicon Crystals from the Vapor

A review of inorganic fibers other than asbestos, glass, and carbon fibers and optical and hollow fibers. Special emphasis is placed on high-performance fibers. The manufacture, structure, properties, and uses of the selected fibers are discussed.

Inorganic Fibers—A Literature Review

Crystals of a variety of substances including elements, minerals, simple salts, organic molecular crystals, and high polymers forgo long-range translational order by twisting and bending as they grow. These deviations have been observed in crystals ranging in size from nanometers to centimeters. How and why so many materials choose dramatic non-crystallographic distortions is analyzed, with an emphasis on crystal chemistries that give rise to stresses operating either on surfaces of crystallites or within the bulk.

Growth Actuated Bending and Twisting of Single Crystals

https://science.sciencemag.org/content/sci/128/3324/569.full.pdf

Growth and Properties of "Whiskers": Further research is needed to show why crystal filaments are many times as strong as large crystals.

Examination of small euhedral crystals of α‐Al2O3 (sapphire) that were observed following oxidation of aluminum and an aluminum alloy in wet hydrogen at high temperatures showed that growth probably occurs by decomposition of AlO on an Al2O3 surface. Rapid growth occurs on the tips of needles and the edges of platelets at lattice steps formed by intersection of hollow screw dislocations with these surfaces. Screw dislocations were detected by x‐ray measurement of the lattice twist they produce in the needle‐like crystals or ``whiskers.'' Needles were bent to elastic strains of over 2% corresponding to a strength of 1011 dyne cm−2.

W. W. Webb

Papers

Growth and Defect Structure of Sapphire Microcrystals