Growth of Pentacene Crystals by Naphthalene Flux Method.

We report the crystal growth of pentacene from a solution of naphthalene. The solubility of pentacene in naphthalene was evaluated by optical absorption at elevated temperature. The crystal growth was performed in an H-shaped sealed glass tube or metal vessels sealed with ultrahigh-vacuum compatible flanges placed in heated two-zone aluminum blocks. The obtained crystals had a single-crystal-like appearance and flat surface. They were made of aligned microtwins of the "bulk type" (interlayer spacing 14.5 Å) polymorph.