Direct Production of Spectroscopic Specimens from Single Crystals by Controlled Growth from a Vapor

Abstract

Studies of anisotropic infrared absorption demand quite thin sections of single crystals, having relatively large cross section parallel with one of the few spectroscopically significant planes. This article describes the principles of design, the construction, and the successful operation with benzene of an apparatus for producing such specimens of single crystals. The method involves gradual introduction of vapor into an enclosed space, supporting a gradient of temperature and having the shape desired for the specimen, until self‐nucleation occurs in a small vicinity of the colder pole of temperature. Processes of attrition among the nuclei ensue automatically and instantaneously, resulting in the survival of only those that become attached to the confining wall with a most favored orientation, an orientation that can be selected to some degree by factors of design and operation. Thereafter, vapor issuing into the enclosure accretes upon the few surviving nuclei until these seeds coalesce and develop to fill the entire volume available. The method promises to be especially useful for producing and investigating crystals that exist only at low temperatures.