Pentacene Thin Film by Compact Thermal Evaporation System

Abstract

A compact thermal evaporation technique was used to fabricate pentacene thin films from a pure (99%) powder. All of the samples were grown at ambient temperature on glass substrates coated with indium tin oxide (ITO), and their optical, structural, and electrical properties were investigated. UV-visible (UV-Vis) spectroscopy and photoelectron spectroscopy in atmosphere (PESA) methods were used to evaluate the optical properties of a pentacene thin film utilising experimental values of optical band gap and ionisation potential. The energy band diagram of the highest occupied molecular orbital - lowest unoccupied molecular orbital (HOMO-LUMO) level depicts the electronic structure of pentacene. The HOMO and LUMO energy levels were determined toward being -5.49 eV and -3.74 eV, respectively, while the optical bandgap was 1.75 eV. Then, X-ray diffraction (XRD) was used to examine the structural properties of a thermally evaporated pentacene thin film. The XRD analysis revealed the bulk phase thin films oriented along the (001) plane direction. Finally, metal/pentacene/metal structured device was fabricated and showed a rectifying behavior.