Nonvolatile transistor memory devices based on high-k electrets of polyimide/TiO₂ hybrids

Novel nonvolatile memory behaviors of n-type N,N′-bis(2-phenylethyl)-perylene-3,4,9,10-tetracarboxylic diimide (BPE-PTCDI) based organic field-effect transistors (OFET) using the new polyimides (PIs), (poly[9,9-bis(4-(4-amino-3-hydroxyphenoxy)phenyl)fluorene-oxydiphthalimide]) PI(F-ODPA) and (poly[4,4′-bis(4-amino-3-hydroxyphenylthio)diphenyl sulfide-oxydiphthalimide]) PI(3S-ODPA), and their PI/TiO₂ hybrids as electrets are reported. The OFET memory devices derived from PI(F-ODPA) with π-conjugated fluorene moieties exhibited a larger memory window (8.6 V), and could be further enhanced by introducing TiO₂ (up to 20 wt%) into the PIs. In addition, PI/TiO₂ hybrids as electrets for memory devices also could effectively reduce the operating voltage, indicating that the charge transfer capability of TiO₂ plays an important role in transferring and storing the charge for OFET memory devices.