Enhancement of the hole mobility and concentration in pentacene by oxygen plasma treatment

X-ray photoelectron spectroscopy, atomic force microscopy and Hall-effect measurements were used to characterize the pentacene (PEN) films with and without oxygen plasma treatment. We found that the hole mobility (hole concentration) of the PEN film following oxygen plasma treatment could achieve as high as 12.3 ± 0.5 cm² V^{- 1} s^{- 1} [(2.9 ± 0.3) × 10¹³ cm^{- 3}]. This is because of the incorporation of oxygen in the PEN film and the passivation of the defects in the grain-boundary region. In addition, the use of oxygen plasma significantly improves conductivity while having no impact on surface roughness (or crystallite size).