Synthesis and Memory Device Characteristics of New Sulfur Donor Containing Polyimides

The synthesis and memory device characteristics of two new poly[2,7-bis(phenylenesulfanyl) lthianthrene-hexafluoroisopropylidenediphtalimide] (APTT-6FDA) and poly[4,4'-thiobis(p-phenylene-sulfanuyl)-hexafluoroisopropylidenediphthalimide] (3SDA-6FDA) are reported. The sulfur-containing APTT and 3SDA as electron donor were designed to enhance electron-donating and charge-tran sporting characteristics for the device application. The optical band gaps of APTT-6FDA and 3SDA-6FDA estimated from the absorption edges were 3.51 and 3.46 eV. which probably resulted from the difference in the structural coplanarity. The estimated energy levels (HOMO, LUMO) of APTT-6FDA and 3SDA-6FDA were (-5.55. -2.04) and (-5.71, -2.25) eV, respectively. The memory device with I lie configuration of ITO/polymers/Al showed nonvolatile memory characteristics with the low turn-on threshold voltages of 1.5 V(APTT-6FDA) and 2.5 V(3SDA-6FDA), probably resulting from the difference in the HOMO energy level. Also. the memory devices could be repeatedly written, read, and erased. The on/off Current ratios of the devices were all around 10(4) in ambient atmosphere. The relatively higher dipole moments of the sulfur-containing polyimides compared to the triphenylaimne-based polyimide provided a stable CT complex for the flash memory device. The above electronic properties were further confirmed by the density functional theory (DFT) method at the B3LYP level with the 6-31G(d) basis set. The present study suggested that the new sulfur-containing polyimides would have potential applications for memory devices.