Arrays of Pentacene Single Crystals by Stencil Evaporation

Abstract

In order to realize high-performance organic thin-film transistors (TFT), two parameters of the organic semiconducting layer are desired: single crystallinity for high mobility and patterning for low off currents. High-quality single crystals can be fabricated using vapor techniques such as physical vapor transport (PVT), but they require high temperatures close to thermodynamic equilibrium, for example, 240 °C for pentacene. Such high temperatures are not ideal for TFT fabrication on plastic substrates and limit the use of PVT in flexible electronics applications. In this work arrays of pentacene single crystals were directly deposited at low temperature of 40 °C by vacuum thermal evaporation through microfabricated stencil masks (stencil lithography). By decreasing the stencil aperture size down to 1 μm × 1 μm, we were able to limit the nucleation area until only one grain per aperture is nucleated and grown. We studied systematically scaling effects for large singe crystal growth and discuss details of...