Bidirectional mediation of TiO₂ nanowires field effect transistor by dipole moment from purple membrane

Bacteriorhodopsin-embedded purple membrane (bR-PM) is one of the most promising biomaterials for various bioelectronics applications. In this work, we demonstrate that a dipole bio-originated from bR-PM can bidirectionally mediate the performance of a bottom-contact TiO₂ nanowire field effect transistor (FET) for performance improvement. When negative gate voltage is applied, both transfer and output characteristics of the TiO₂ nanowire FET are enhanced by the bR-PM modification, resulting in a hole mobility increased by a factor of 2. The effect of the number of the deposited bR-PM layers on the normalized ΔI_D of the FET suggests that the additional electric field generated by the dipole moment natively existing in bR-PM actually boosts the performance of the TiO₂ nanowires FET.