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Data retention characteristics and a failure mechanism of TaN/CuxO/Cu resistive memory device are investigated by a temperature-accelerated test method. Data retention capability at 85 °C is sufficiently longer than 10 years by using two different methods: simple extrapolation and Arrhenius equation. The high resistance state fails to low resistance state and low resistance state fails to high resistance state at the elevated temperature. It is attributed that different retention-failure mechanisms are responsible for high resistance state and low resistance state, respectively. A filament/charge trapped combined model is presented to clarify the retention-failure mechanism. [ABSTRACT FROM AUTHOR]

The compliance-current dependence of the resistive-switching behaviors is investigated in TaN/CuxO/Cu memory devices with 1R architecture and 1T1R architecture, respectively. The correlation of reset current Ireset and ON-state resistance Ron can be verified by adjusting the compliance current Icomp. Meanwhile, Ireset and Ron become independent on Icomp in the 1R architecture when Icomp is below 1 mA. A serious compliance-current overshoot phenomenon is in situ observed in 1R-architecture device, and it remarkably affects the resistive-switching characteristics because the compliance current dominates the memory behaviors. Therefore, resistive-switching investigation based on 1T1R architecture is much more reliable. [ABSTRACT FROM AUTHOR]

We investigated the switching performance of Cu-oxide films with Al, Pt, and Ti electrodes. Compared with Pt electrode, the Al electrode shows better stability, preferable endurance, and larger resistance ratio. An interface AlOx layer is detected by transmission electron microscopy and Auger electron spectroscopy. This layer can strongly affect the movement of oxygen vacancies. However, the sample with pure Ti electrode almost has no switching characteristics. Ti/TiN electrode with thin Ti exhibits good switching behavior. The thickness control of Ti layer is quite critical. So we suggest that the oxygen diffusion in electrode is another important factor for switching performance. [ABSTRACT FROM AUTHOR]

The authors found CuOx thin film with gradual oxygen concentration (GOC) distribution enhances resistive switching characteristics for nonvolatile memory applications. By using Al/GOC CuOx/Cu structure, not only no forming is needed but also the endurance of switching is greatly enhanced. The device with GOC CuOx demonstrates resistance on/off ratio of greater than 100 and endurance of more than 12 000 cycles. The “forming-free” characteristics appear related to thinner CuO and the endurance enhancement appears related to gradual gradient of oxygen vacancies in CuOx. Thus, the thickness of CuO and distribution of oxygen (as well as vacancies) play important roles for performance improvement. [ABSTRACT FROM AUTHOR]

Mutational replacements of specific residues in the GTP-binding pocket of the 21-kDa ras proteins (p21ras) reduce their GTPase activity. To test the possibility that the cognate regions of G protein alpha chains participate in GTP binding and hydrolysis, we compared signaling functions of normal and mutated alpha chains (termed alpha s) of Gs, the stimulatory regulator of adenylyl cyclase. alpha s chains were expressed in an alpha s-deficient S49 mouse lymphoma cell line, cyc-. alpha s in which leucine replaces glutamine 227 (corresponding to glutamine 61 of p21ras) constitutively activates adenylyl cyclase and reduces the kcat for GTP hydrolysis more than 100-fold. There is a smaller reduction in GTPase activity in another mutant in which valine replaces glycine 49 (corresponding to glycine 12 of p21ras). This mutant alpha s is a poor activator of adenylyl cyclase. Moreover, the glycine 49 protein, unlike normal alpha s, is not protected against tryptic cleavage by hydrolysis resistant GTP analogs; this finding suggests impairment of the mutant protein's ability to attain the active (GTP-bound) conformation. We conclude that alpha s residues near glutamine 227 and glycine 49 participate in binding and hydrolysis of GTP, although the GTP binding regions of alpha s and p21ras are not identical.