Elastomeric Transistor Stamps: Reversible Probing of Charge Transport in Organic Crystals

We introduce a method to fabricate high-performance field-effect transistors on the surface of freestanding organic single crystals. The transistors are constructed by laminating a monolithic elastomeric transistor stamp against the surface of a crystal. This method, which eliminates exposure of the fragile organic surface to the hazards of conventional processing, enables fabrication of rubrene transistors with charge carrier mobilities as high as$\sim 15 cm^2/V\cdot s$and subthreshold slopes as low as$2 nF\cdot V/decade\cdot cm^2$. Multiple relamination of the transistor stamp against the same crystal does not affect the transistor characteristics; we exploit this reversibility to reveal anisotropic charge transport at the basal plane of rubrene.