Ultrathin organic single crystals: fabrication, field-effect transistors and thickness dependence of charge carrier mobility

Organic single crystals with thickness ranging from a few monolayers to micrometres were fabricated by an Organic Crystal Cleavage method. The mobility slightly increased with decreased thickness and rose sharply when the crystal thickness was below some critical thickness. The gate induced charges in the field-effect transistor (FET) channel and in the vicinity of the metal-semiconductor interface reducing the contact barrier. The values of mobility measured on very thin crystals without the contact barrier precisely reflect the transport properties of organic semiconductors.