Correlation of growth of pentacene films at various gas ambience conditions to organic field-effect transistor characteristics

Pentacene based thin-film transistors (TFTs) have been fabricated using pentacene films grown under various ambiences, such as N₂, H₂, Ar, He, and high vacuum, to define correlation of the device performance, in particular mobility properties, to molecular ordering in pentacene films. The field-effect mobility of 0.24 cm²/Vs was obtained from TFTs fabricated under 2 × 10^-5 Torr nitrogen ambience, however, the pentacene TFTs fabricated in hydrogen ambience under the same pressure yielded very poor mobility of 0.008 cm²/Vs. Pentacene films deposited by thermal evaporation at increased pressure in nitrogen ambience have a high degree of molecular ordering with larger dendritic grains without any surface modification on silicon oxide dielectric. A clean relation between field-effect mobility and XRD estimated crystallites size was obtained.