Comparison of the Purity and Perfection of Vapor‐ and Melt‐Grown Anthracene Crystals

Abstract

The purity and perfection of anthracene crystals have been examined for melt‐grown and thick ( > 1 mm) vapor‐grown crystals. The physical properties studied were the charge carrier lifetime and mobility of holes, dislocation density, and the bulk self‐diffusion coefficient. Chemical purity was assessed by gas chromatography. Melt‐grown crystals had hole lifetimes > 1 msec compared with 220 μsec for the best vapor‐grown crystal, although vapor‐grown crystals had lower dislocation densities and fewersubboundaries. Vapor‐grown crystals had lower measurable impurity concentrations, ∼2 ppm compared with ∼10 ppm for melt‐grown crystals, but these impurities appear to have no effect on charge carrier trapping. Both types of crystals gave the same self‐diffusion coefficient at 190°.