Mesophase Semiconductors and the Field Effect Transistors

Here we show the simple fabrication of field effect transistor (FET) with a mesophase semiconductor, a derivative of dithienyl naphthalene, which exhibits a fast mobility (10 -1 ~ 10 -2 cm 2 V -1 s -1 ) of charged carriers in the mesophase. The compound is a mesogen, but with highly ordered layered structure in a triclinic lattice, meaning a 3D-mesophase is formed. The device performance was studied for the transistor mobility, on/off ratio and threshold voltage of device operation, to have 0.14 cm 2 V -1 s -1 , 2 x 10 3 and -27 V at room temperature (in a crystal phase), respectively, even though the thin film active layer (100 nm thick) does have a multi-domain system. However, the XRD studies indicate the uniformly aligned molecules in each domain, of which long axis is inclined to be ca. 27° against the axis perpendicular to the substrate plane. This implies that a self-assembling nature of mesogenic molecules is a certain merit for thin film device fabrication in organic electronics.