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.