A new solution of the Einstein-Maxwell equations is presented. This solution has certain characteristics that correspond to a rotating ring of mass and charge.

Resistive switching memories (RRAMs) are attractive for replacement of conventional flash in the future. Although different switching materials have been reported; however, low-current operated devices (<100 μA) are necessary for productive RRAM applications. Therefore, TaOx is one of the prospective switching materials because of two stable phases of TaO2 and Ta2O5, which can also control the stable low- and high-resistance states. Long program/erase endurance and data retention at high temperature under low-current operation are also reported in published literature. So far, bilayered TaOx with inert electrodes (Pt and/or Ir) or single layer TaOx with semi-reactive electrodes (W and Ti/W or Ta/Pt) is proposed for real RRAM applications. It is found that the memory characteristics at current compliance (CC) of 80 μA is acceptable for real application; however, data are becoming worst at CC of 10 μA. Therefore, it is very challenging to reduce the operation current (few microampere) of the RRAM devices. This study investigates the switching mode, mechanism, and performance of low-current operated TaOx-based devices as compared to other RRAM devices. This topical review will not only help for application of TaOx-based nanoscale RRAM devices but also encourage researcher to overcome the challenges in the future production.

Aggarwal, S.; Yang, B.; Wuttig, M.; Ramesh, R.; Auciello, O.; and Venkatesan, T., "Nanoscale imaging of domain dynamics and retention in ferroelectric thin films" (1997). Alexei Gruverman Publications. 3.

Multilevel cell (MLC) storage technology is attractive in achieving ultrahigh density memory with low cost. In this letter, we have demonstrated 3-bit per cell storage characteristics in a TaO x -based RRAM. By analyzing the key requirements for MLC operation mainly the switching uniformity and stability of resistance levels, an engineered stack based on thermodynamics in top electrode/(vacancy reservoir/defect control layer)/switching layer/bottom electrode structure was designed. In the optimized stack with ∼10-nm Ta layer incorporated at W/TaO x interface, seven low resistance state levels with same high resistance state were obtained by controlling the switching current down from 30 µA enabling low power 3-bit storage in contrast to the control device which shows 2-bit MLC with resistance saturation. The improved switching and MLC behavior is attributed to the minimized stochastic nature of set/reset operations due to filament confinement by favorable electric field generation and formation of thin but highly conductive filament which is confirmed electrically. Index Terms-Multi-level cell, RRAM, TaO x , vacancy reservoir, defect engineering, dense filament.

The transition metal oxide, NbO2, which exhibits an insulator to metal transition (IMT) is regarded as a promising selector device to be integrated with a resistive memory for cross point array application. In this study, we comprehensively investigated the scaling of an NbO2 selector using a mushroom device structure. A thorough understanding of the scaling behavior of forming voltage (Vf), threshold voltage (Vth), and current (Ith) is essential to evaluate the potential of voltage as well as current scaling and selectivity of NbO2 selector. Importantly, by analyzing the scaling trend of threshold current, we believed that the IMT behavior is strongly affected by filamentary conducting path formed during the forming process. The findings provide the promise to maximize the selector device performance by minimizing the conducting path inside the NbO2 layer.