Operational stability in pentacene thin-film transistors with threshold voltages tuned by oxygen plasma treatment

Pentacene-based organic thin-film transistors (TFTs) having a SiO₂ gate dielectric treated with oxygen plasma have been investigated for control of the threshold voltage. The threshold voltage changed in the wide range from %15 to 80V, depending on plasma treatment time, AC power for plasma generation, and gate dielectric thickness. The threshold voltage change was attributed to negative charges induced on and/or near the surface of the gate dielectric. The threshold voltage change on the order of 1 V was particularly proportional to plasma treatment time. The predictable change enables the control of threshold voltage in this range. In addition, the effect of gate bias stress on threshold voltage was examined. The results suggested that gate bias stress does not negate the threshold voltage change induced by plasma treatment.