Enhancing the ambient-enduring performance of pentacene thin-film transistors by SnO₂-encapsulation

Pentacene thin-film transistors (TFTs) encapsulated with a transparent SnO₂ thin-film prepared by ion-beam-assisted deposition (IBAD) were fabricated. We deposited a thermally evaporated 100 nm SnO₂ film on a pentacene TFT prior to IBAD as a buffer layer. After encapsulation, our TFT showed initial degradation in terms of field-effect mobility (from 0.62 to 0.5 cm²/V s). However, the mobility of 0.5 cm²/V s was sustained up to 1 month in air and before degrading to 0.35 cm²/V, which is but three times higher than that of a reference TFT without no encapsulation treatment. Under the SnO₂ encapsulation, on/off current ratio was also maintained at over 10⁵ which was initially ∼ 10⁶, while the unprotected device displayed less than ∼ 10⁴. Our work demonstrates that the IBAD SnO₂ encapsulation is a promising technique for long-term protection of a pentacene TFT.