We have fabricated electrically programmable memory devices with thermally and dimensionally stable poly(N-(N',N'-diphenyl-N'-1,4-phenyl)-N,N-4,4'-diphenylene hexafluoroisopropylidene-diphthalimide) (6F-2TPA PI) films and investigated their switching characteristics and reliability. 6F-2TPA PI films were found to reveal a conductivity of 1.0 x 10(-13)-1.0 x 10(-14) S cm(-1). The 6F-2TPA PI films exhibit versatile memory characteristics that depend on the film thickness. All the PI films are initially present in the OFF state. The PI films with a thickness of >15 to <100 nm exhibit excellent write-once-read-many-times (WORM) (i.e. fuse-type) memory characteristics with and without polarity depending on the thickness. The WORM memory devices are electrically stable, even in air ambient, for a very long time. The devices' ON/OFF current ratio is high, up to 10(10). Therefore, these WORM memory devices can provide an efficient, low-cost means of permanent data storage. On the other hand, the 100 nm thick PI films exhibit excellent dynamic random access memory (DRAM) characteristics with polarity. The ON/OFF current ratio of the DRAM devices is as high as 10(11). The observed electrical switching behaviors were found to be governed by trap-limited space-charge-limited conduction and local filament formation and further dependent on the differences between the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels of the PI film and the work functions of the top and bottom electrodes as well as the PI film thickness. In summary, the excellent memory properties of 6F-2TPA PI make it a promising candidate material for the low-cost mass production of high density and very stable digital nonvolatile WORM and volatile DRAM memory devices.

A series of aromatic polyimides (PIs) were synthesized via the polymerization of 3,3′,4,4′-diphenylsulfonyltetracarboxylic dianhydride with 4,4′-diaminotriphenylamine derivatives containing hydrogen, cyano, methoxy, or dimethylamine substituents. These PIs were thermally and dimensionally stable and produced high-quality thin films when applied in a conventional spin-coating process. Their structure and properties were characterized. Nanoscale thin films of the PIs demonstrated excellent electrical memory performance, with high stabilities and ON/OFF current ratios. The memory characteristics were found to be tunable by varying the substituents; nonvolatile write-once–read-many-times memory behavior, nonvolatile ON/OFF switching type memory behavior, and volatile dynamic random access memory behavior were observed. The memory characteristics were substantially influenced by the electron-accepting cyano- and electron-donating dimethylamine substituents but were apparently not affected by the electron-donating methoxy substituent. In addition, the film density was a significant factor influencing the observed memory behaviors, with larger film densities causing lower OFF-current levels. However, the critical switching-on voltage varied very little as the substituents were changed and was measured to be approximately ±2 V. All of the memory behaviors were found to be governed by a mechanism involving trap-limited space-charge-limited conduction and local filament formation. Overall, all of the PIs assessed in the present work were found to be suitable active materials for the low-cost mass production of high-performance, programmable unipolar memory devices that can be operated with very low power consumption, high ON/OFF current ratios, and high thermal and dimensional stability.

Synthesis of graphene that contains boron and nitrogen is still a big challenge. In this paper, we report the growth of boron (B)-and nitrogen (N)-doped graphene on a Pt(111) surface by graphenization of a novel molecule, hexaphenylborazine (HPB). We performed quantum chemical calculations for the molecule and compared the results with the photoelectron spectra. Deposition of HPB onto the heated Pt(111) substrate led to formation of the doped graphene. Incorporation of nitrogen and boron atoms to the graphene lattice was observed up to the substrate temperature of 600 °C and at 400 °C, respectively. On the basis of the experimental results and Mulliken population analysis, we discuss the possible atomic configuration of B,N-doped graphene.

A high-performance ORR catalyst has been synthesised by pyrolysis of quaternary nitrogen-containing 4a,8a-diazoniapentaphene dibromide (DAP), phenolic resin and FeBr 2 mixture. The catalyst (Fe/DAP) was characterized by XPS, SEM and TEM analysis. The ORR activity was studied using rotating ring-disk electrode voltammetry (RRDE) and the onset potential of ORR was found to be 0.95 V vs. RHE in 0.5 M H 2 SO 4 solution, which is very close to that of the state-of-the-art Pt/C catalyst. The stability of the catalyst was studied using LD and SSD tests and found to be highly stable even after 11 110 potential-steps in the LD test. The kinetic and mechanistic analyses of the ORR on the catalyst indicate that the ORR, as a whole, follows a 4-electron (parallel) pathway. The relative changes in the nitrogen content after the durability test was estimated using N 1s XPS spectra which may be associated with the activity loss after the durability test. The loss of ORR activity was observed after the acid washing of the catalyst which suggests the role of Fe in the direct 4-electron reduction of O 2 .

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