Pentacene-Based Low-Voltage Strain Sensors With PVP/ $\hbox {Ta}_{2}\hbox {O}_{5}$ Hybrid Gate Dielectrics

Field-controllable pentacene-semiconductor-based strain sensors were fabricated with hybrid gate dielectrics using polyvinyl phenol (PVP) and high-k inorganic tantalum pentoxide (Ta₂O₅) onto polyethylene naphthalate films. The Ta₂O₅ gate-dielectric layer combined with a thin PVP layer to form very smooth and hydrophobic surfaces turns out to improve the molecular structures of pentacene films significantly. The PVP-Ta₂O₅ hybrid-gate-dielectric films exhibit a high dielectric constant of 19.27 and a leakage-current density of as low as 100 nA/cm² . The sensors employing a thin-film-transistor-like Wheatstone bridge configuration able to operate at reduced voltage (~ 4 V) show good device characteristics with a field-effect mobility of 1.89 cm²/V · s and a threshold voltage of -0.5 V. The strain sensor characterized with bending at 45° with respect to the bridge bias direction with different bending radii of 50-, 40-, 30-, 20-, and 8-mm displays output signals improved in linearity in a low range of operating voltages.