A review on polymeric charge storage electrets for constructing non-volatile organic field effect memory devices is presented.

The molecule 2-methylmalonaldehyde (2-MMA) exists in the gas phase as a six-membered hydrogen-bonded ring [HO-CH=C(CH(3))-CH=O] and exhibits two large-amplitude motions, an intramolecular hydrogen transfer and a methyl torsion. The former motion is interesting because the transfer of the hydrogen atom from the hydroxyl to the carbonyl group induces a tautomerization in the ring, i.e., HO-CH=C(CH(3))-CH=O-->O=CH-C(CH(3))=CH-OH, which then triggers a 60 degrees internal rotation of the methyl group attached to the ring. The microwave spectra of 2-MMA-d0, 2-MMA-d1, and 2-MMA-d3 were studied previously by Sanders [J. Mol. Spectrosc. 86, 27 (1981)], who used a rotating-axis-system program for two-level inversion problems to fit rotational transitions involving the nondegenerate A(+) and A(-) sublevels to several times their measurement uncertainty. A global fit could not be carried out at that time because no appropriate theory was available. In particular, observed-minus-calculated residuals for the E(+) and E(-) sublevels were sometimes as large as several megahertz. In the present work, we use a tunneling-rotational Hamiltonian based on a G(12) (m) group-theoretical formalism to carry out global fits of Sanders' 2-MMA-d0 and 2-MMA-d1 [DO-CH=C(CH(3))-CH=O] spectra nearly to measurement uncertainty, obtaining root-mean-square deviations of 0.12 and 0.10 MHz, respectively. The formalism used here was originally derived to treat the methylamine spectrum, but the interaction between hydrogen transfer and CH(3) torsion in 2-MMA is similar, from the viewpoint of molecular symmetry, to the interaction between CNH(2) inversion and CH(3) torsion in methylamine. These similarities are discussed in some detail.

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We report the nonvolatile memory characteristics 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 polyimide electrets of poly[2,5-bis(4-aminophenylenesulfanyl)selenophene–hexafluoroisopropylidenediphthalimide] (PI(APSP-6FDA)), poly[2,5-bis(4-aminophenylenesulfanyl)thiophene–hexafluoroisopropylidenediphthalimide] (PI(APST-6FDA)), and poly(4,4′-oxidianiline-4,4′-hexafluoroisopropylidenediphthalic anhydride) (PI(ODA-6FDA)). Among those polymer electrets, the OFET memory device based on PI(APSP-6FDA) with a strong electron-rich selenophene moiety exhibited the highest field-effect mobility and Ion/Ioff current ratio of 105 due to the formation of the large grain size of the BPE-PTCDI film. Furthermore, the device with PI(APSP-6FDA) exhibited the largest memory window of 63 V because the highest HOMO energy level and largest electric filed facilitated the charges transferring from BPE-PTCDI and trapping in the PI electret. Moreover, the charge transfer from BPE-PTCDI to the PI(APSP-6FDA) or PI(APST-6FDA) electrets was more efficient than that of PI(ODA-6FDA) due to the electron-donating heterocyclic ring. The nanowire device with PI(APSP-6FDA) showed a relatively larger memory window of 82 V, compared to the thin film device. The present study suggested that the donor–acceptor polyimide electrets could enhance the capabilities for transferring and store the charges and have potential applications for advanced OFET memory devices.

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