Pentacene nanostructures on surface-hydrophobicity-controlled polymer/SiO₂ bilayer gate-dielectrics

Crystalline morphologies and structures of pentacene in thin films that are vacuum-deposited on a surface-hydrophobicity-controlled ultrathin polymeric layer/300 nm thick Si0₂ bilayer gate-dielectrics with similar surface roughness was reported. Polystyrene (PS), poly(4-hydroxyl styrene) (PHS), and poly(4-vinyl pyridine) (PVP) thin layers were spin-cast onto thermally grown 300 nm thick SiO₂ substrates, followed by annealing. On the bilayer gate dielectrics, pentacene films were thermally evaporated at a substrate temperature of 30°C. Diffractions of Bragg rods (BRs) that arise from in-plane molecular packing are observed along the substrate normal and exhibit slow variations that indicate no evidence of interlayer correlation. 2D GIXD patterns for the PHS/Si0₂ and PVP/Si0₂ clearly reveal the coexistence of two crystalline phases, which have different interlayer spacings and layer orientation with respect to the substrate.