Sub-A resolution electron density analysis of the surface of organic rubrene crystals.

The electron density distribution of an organic semiconductor is observed as a function of the depth from the crystal surface or interface. The surface x-ray scattering technique combined with a recently developed analyzing technique, coherent Bragg rod analysis, enables us to observe the electron density profile. The obtained near-surface electron density profile of a single crystal of rubrene, which is known as a high-mobility organic transistor material, shows not only a large positional distribution of the molecules at the surface, but also a sub-A molecular deformation that affects the molecular orbital.