Temperature-dependent pentacene nanostructures on hydrophobic gate-dielectrics correlated with charge carrier mobilities

Crystalline nanostructures of pentacene thin films on octadecyltrichlorosilane-treated dielectrics, held at various substrate deposition temperatures (T(D)s), have been correlated with charge mobilities in the 60 nm thick pentacene-based field-effect transistors. On the gate-dielectrics held at T-D <= 60 degrees C, the first pentacene seeding crystals tend to grow with layer-by-layer mode, while at TD > 60 C they start to grow with island mode, affecting the subsequently growing crystal structure. Grazing-incidence X-ray diffraction shows that with an increase in TD a surface-induced "thin film phase" competes with a triclinic "bulk phase", which significantly interferes lateral pi-conjugation of pentacene due to different polymorphic structures.