Nucleation and Growth of Molecular Organic Crystals in a Liquid Film under Vapor Deposition

We report on the nucleation and growth of tetracene in a thin liquid film which is continuously supersaturated by vapor deposition of molecules onto the film. In a first stage, nucleation and fast anisotropic two-dimensional dendritic growth occurs. In a second stage, the dendrites coarsen into pallet-shaped crystals. These are highly oriented with respect to the plane of the liquid film and reach a lateral size of several $100\mu \mathrm{m}$. The two-dimensional growth mode is explained by the confined growth geometry in the liquid in combination with the anisotropy of the crystal structure.