Pentacene organic field-effect transistor on metal substrate with spin-coated smoothing layer

In this letter we report the use of roughly polished aluminum substrates with spin-coated polymer-smoothing layers for the fabrication of pentacene field-effect transistors. Transistors with spin-coated poly(methylmethacrylate) gate insulator layers were fabricated and showed good performance. On the gate insulator surface, the root-mean-square roughness was found to be $0.18\mathrm{nm}$ , significantly smaller than the aluminum surface roughness, which is on the scale of tens of nanometers. Field-effect carrier mobilities extracted from the device data reached $0.75{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ ; the maximum on/off current ratio was near $5\times {10}^6$ .