The liquid-phase deposition method for growing silicon dioxide interlayers on O-2/Ar plasma pretreatment plastic substrates is investigated. The authors found that the ratio of COO (288.9 eV) to CH2(284.5 eV) increases with the O-2/Ar plasma pretreatment as indicated by x-ray photoelectron spectroscopy. Upon treatment, the interlayer on the plastic substrate is grown, and the quality of the film on the substrate with or without plasma pretreatment is examined by using scanning electron microscopy, etching rate of the oxide layer by dilute HF solution, and surface leakage current measurement. Pentacene-based organic thin-film transistors on dielectric layers are demonstrated. Finally, they also found that this coating can enhance optical transmittance, as demonstrated by ultraviolet-visible spectroscopy measurement. (C) 2007 American Vacuum Society.