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A comprehensive understanding of the disorder-induced transport characteristics in resistive random-access memory (RRAM) is critical for its thermal stability analysis and analog switching for the coming neuromorphic computing application. Superior to the previous transport mechanisms which are only valid within their respective ranges of temperatures, we propose a unified physics-based model that can accurately predict the transport dependence on all temperature ranges up to 300 K. By utilizing percolation theory and the Fermi Golden Rule, the probability distributions for both the tunnel junction energy barrier and gap distance based statistical resistance model are described. It is found that different programming cycles and resistance states contribute to transition behavior between various low-temperature transport mechanisms. Moreover, the model can also investigate the dependence of electrical characteristics on defect generation like radiation damage. Therefore, it quantitatively relates the thermal stability and percolation effects to the structural disorders in RRAM. The good agreement between the simulation and experimental results indicates that our physics-based model can provide an accurate prediction of temperature and disorder dependent effects in RRAMs. [ABSTRACT FROM AUTHOR]

Since it is undesirable to require an external magnetic field for on-chip memory applications, we investigate the use of a Rashba effective field alternatively for assisting the electric-field-induced switching operation of a three terminal perpendicular magnetic tunnel junction (pMTJ). By conducting macro-spin simulations, we show that a pMTJ with a thermal stability of 61 can be switched in 0.5 ns, consuming a switching energy of 6 fJ, and the voltage operation margin can be improved to 0.8 ns. Furthermore, the results also demonstrate that a heavy metal system that can provide a large field-like torque rather than the damping-like torque is favored for the switching. [ABSTRACT FROM AUTHOR]

We investigate thermally induced currents in a zigzag graphene nanoribbon (ZGNR) heterostructure, consisting of hydrogen-terminated ZGNR (ZGNR-H) and oxygen-terminated ZGNR (ZGNR-O), under different electronic and magnetic states. Compared to a pure ZGNR-H system, the heterostructure displays a considerably larger thermally induced current due to its asymmetric transmission spectrum. Moreover, the magnetized ZGNR-H/ZGNR-O shows spin filter and magnetoresistance effects, suggesting potential applications of the ZGNR-H/ZGNR-O heterostructures in thermoelectric and spintronics devices. [ABSTRACT FROM AUTHOR]

The thermal stability and electronic structures of two dimensional Cx(BN)y compounds are studied using first-principles calculations based on the density functional theory. Although, from total energy calculations, it was well-established that phase-segregated atomic arrangements had the lowest energy, we found that due to the high activation energy required for phase-segregation process, evenly distributed configurations are stable at room temperature. Furthermore, the energy bandgap (EG) of the evenly distributed Cx(BN)y compounds is dependent on the carbon concentration. By controlling the carbon concentration in the compound, the EG of the compound material can be adjusted for electronic applications. [ABSTRACT FROM AUTHOR]

Reproducible current hysteresis is observed in graphene with a back gate structure in a two-terminal configuration. An opposite sequence of switching with different charge carriers, holes, and electrons is found. The charging and discharging effect is proposed to explain this ambipolar bistable hysteretic switching. To confirm this hypothesis, one-level transport model simulations including charging effect are performed and the results are consistent with our experimental data. Methods of improving the on/off ratio of graphene resistive switching are suggested. [ABSTRACT FROM AUTHOR]

Negative differential conductance and tunneling characteristics of two-terminal graphene devices are observed before and after electric breakdown, respectively. The former is caused by the strong scattering under a high E-field, and the latter is due to the appearance of a tunneling barrier in graphene channel induced by a structural transformation from crystalline graphene to disordered graphene because of the breakdown. Using Raman spectroscopy and imaging, the presence of nonuniform disordered graphene is confirmed. A memory switching effect of 100 000% ON/OFF ratio is demonstrated in the tunneling regime, which can be employed in various applications. [ABSTRACT FROM AUTHOR]