Step-Edge-Induced Patterning and Orientation Control of Crystalline Organic Semiconductor Films

Orientation control over micropatterned crystalline organic semiconductor film is crucial to achieve high device performance with small variation in organic electronics. Here, using Au patterned SiO2 substrates, a method is reported to realize high-resolution patterning and orientation control of crystalline organic thin films simultaneously. The vacuum deposited N,N-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C-8) molecules can selectively diffuse to and nucleate on prepatterned Au stripes, resulting in patterned crystalline films with a preferential orientation distribution. Scanning tunneling microscope and high-resolution atomic force microscope images reveal that the PTCDI-C-8 molecules first assemble on Au with perylene diimide cores in a laying down configuration, providing nucleation sites at the step edges for directional growth along the a-axis of the molecule crystal. Subsequent deposition of molecules leads to orientated crystalline films growth due to the pi packing of the perylene diimide cores, resulting in orientation control on micropatterned crystalline films. The finding provides a new strategy to grow oriented crystalline films for high device performance uniformity.