Aging Susceptibility of Terrace-Like Pentacene Films

Structural and chemical changes of aged terrace-like pentacene films have been investigated using grazing-incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The electrically active pentacene nanolayers on the dielectric substrate are susceptible to the oxidative degradation upon aging in air because the near-substrate grain boundaries between the terrace-like domains are well exposed to light and air during aging. GIXD and AFM for pentacene films have been used to elucidate the structural changes, locally initiated at the edges of terraced layers of pentane films upon aging-related oxidative degradation. XPS has revealed the chemical nature of pentacene oxidation upon aging, suggesting the development of hydroxyl and carbonyl groups during aging with light in air. Finally, we have investigated how the structural and chemical degradation of the aged pentacene films reduces the charge mobility and on-off ratio of organic field-effect transistors exposed to light and air.