In situ ultraviolet photoemission spectroscopy measurement of the pentacene-RuO₂/Ti contact energy structure

In situ ultraviolet photoemission spectroscopy was used during the pentacene layer growth on ruthenium and ruthenium oxide films to measure the energy barrier in the metal-semiconductor contact. The measurement showed that ruthenium oxide film formed lower hole-injection barrier with pentacene than ruthenium or gold metal film due to its high work function of 4.92 eV and low resistivity of ∼350 μΩ cm. Pentacene thin film transistor with ruthenium oxide electrode showed higher mobility of 0.435 cm²/V s and on-off ratio of 10⁶ than ruthenium (μ: 0.205 cm²/V s, on/off ratio: 10⁶) or gold electrode (μ: 0.338 cm²/V s, on/off ratio: 10⁶) of the same structure.