Excellent retention characteristics of nanocomposite gate insulator consisting of fullerene-containing polystyrene

Nanocomposite gate insulators were fabricated with functionalized fullerene in a gate insulating polymer [polystyrene (PS) or poly 4-vinyl phenol (PVP)]. An extremely long retention time was obtained for the gate insulating PS, although a larger absolute value of the programming voltage was necessary for the same flatband-voltage shift compared with PVP. The current–voltage characteristics suggested that the level of the lowest-unoccupied molecular orbital of PS was much higher than that of PVP and that this was the reason for the excellent retention characteristics of the fullerene-containing PS. Optimizing the concentration of fullerene molecules in PS will enable fabrication of a practical nanocomposite gate insulator for organic nonvolatile flash memory.