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 $(hbox{Ta}_{2}hbox{O}_{5})$ onto polyethylene naphthalate films. The $hbox{Ta}_{2}hbox{O}_{5}$ 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– $hbox{Ta}_{2}hbox{O}_{5}$ hybrid-gate-dielectric films exhibit a high dielectric constant of 19.27 and a leakage-current density of as low as 100 $hbox{nA/cm}^{2}$ . The sensors employing a thin-film-transistor-like Wheatstone bridge configuration able to operate at reduced voltage ($sim$4 V) show good device characteristics with a field-effect mobility of 1.89 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$ and a threshold voltage of $-$0.5 V. The strain sensor characterized with bending at 45$^{circ}$ 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.