Showing papers by "Yuchao Yang published in 2012"
TL;DR: It is found that the filament growth can be dominated by cation transport in the dielectric film, and two different growth modes were observed for the first time in materials with different microstructures.
Abstract: Nanoscale resistive switching devices, sometimes termed memristors, have recently generated significant interest for memory, logic and neuromorphic applications. Resistive switching effects in dielectric-based devices are normally assumed to be caused by conducting filament formation across the electrodes, but the nature of the filaments and their growth dynamics remain controversial. Here we report direct transmission electron microscopy imaging, and structural and compositional analysis of the nanoscale conducting filaments. Through systematic ex-situ and in-situ transmission electron microscopy studies on devices under different programming conditions, we found that the filament growth can be dominated by cation transport in the dielectric film. Unexpectedly, two different growth modes were observed for the first time in materials with different microstructures. Regardless of the growth direction, the narrowest region of the filament was found to be near the dielectric/inert-electrode interface in these devices, suggesting that this region deserves particular attention for continued device optimization.
940 citations
TL;DR: A tantalum-oxide based resistive memory is reported that achieves the complementary switching functionality within a single memory cell and is accompanied by switching polarity reversal in different voltage bias regimes.
Abstract: Complementary resistive switches (CRS) are considered as a potential solution for the sneak path problem in large-scale integration of passive crossbar resistive memory arrays. A typical CRS is composed of two bipolar memory cells that are connected anti-serially. Here, we report a tantalum-oxide based resistive memory that achieves the complementary switching functionality within a single memory cell. The complementary switching effect is accompanied by switching polarity reversal in different voltage bias regimes. These effects were explained by the redistribution of oxygen vacancies inside the tantalum-oxide layers. The effects of symmetry breaking on bipolar switching and complementary switching were also discussed.
212 citations
TL;DR: In this article, the transition-metal-doped ZnO was used to obtain a series of Zn0.975V0.025O of 170 pC/N, Zn 0.94Cr0.06O of 120 pC /N, and Zn 1.913Mn0 0.087O of 86 p C/N.
Abstract: In recent years, with the growing concerns on environmental protection and human health, new materials, such as lead-free piezoelectric materials, have received increasing attention. So far, three types of lead-free piezoelectric systems have been widely researched, i.e., perovskites, bismuth layer-structured ferroelectrics, and tungsten-bronze type ferroelectrics. This article presents a new type of environmental friendly piezoelectric material with simple structure, the transition-metal(TM)-doped ZnO. Through substituting Zn2+ site with small size ion, we obtained a series of TM-doped ZnO with giant piezoresponse, such as Zn0.975V0.025O of 170 pC/N, Zn0.94Cr0.06O of 120 pC/N, Zn0.913Mn0.087O of 86 pC/N and Zn0.988Fe0.012O of 127 pC/N. The tremendous piezoresponses are ascribed to the introduction of switchable spontaneous polarization and high permittivity in TM-doped ZnO. The microscopic origin of giant piezoresponse is also discussed. Substitution of TM ion with small ionic size for Zn2+ results in the easier rotation of noncollinear TM-O1 bonds along the c axis under the applied field, which produces large piezoelectric displacement and corresponding piezoresponse enhancement. Furthermore, it proposes a general rule to guide the design of new wurtzite semiconductors with enhanced piezoresponses. That is, TM-dopant with ionic size smaller than Zn2+ substitutes for Zn2+ site will increase the piezoresponse of ZnO significantly. Finally, we discuss the improved performances of some TM-doped ZnO based piezoelectric devices.
26 citations
TL;DR: In this paper, a tantalum-oxide based resistive memory that achieves the complementary switching functionality within a single memory cell was presented. But the effect of symmetry breaking on bipolar switching and complementary switching was also discussed.
Abstract: Complementary resistive switches (CRS) are considered as a potential solution for the sneak path problem in large-scale integration of passive crossbar resistive memory arrays. A typical CRS is composed of two bipolar memory cells that are connected anti-serially. Here we report a tantalum-oxide based resistive memory that achieves the complementary switching functionality within a single memory cell. The complementary switching effect is accompanied by switching polarity reversal in different voltage bias regimes. These effects were explained by the redistribution of oxygen vacancies inside the tantalum-oxide layers. The effects of symmetry breaking on bipolar switching and complementary switching were also discussed.
17 citations
TL;DR: In this article, the authors demonstrate that utilizing an external series resistor is not efficient in preventing over-programming and an on-chip resistor is more desirable, and the presence of the onchip resistor enhances the endurance of the RRAM device.
Abstract: Research in non-volatile memories (NVM) has intensified in the past few years due to the ever increasing demand for information storage and the near ubiquity of handheld electronics. Resistive memory is a leading contender in this NVM market due to its high endurance, random accessibility, scalability and low programming voltage. The addition of an external series resistor or imposing current compliance is often used to limit the current through RRAM devices and to prevent “over-programming” and stuck-at-one (SA1) errors. Here, we demonstrate that utilizing an external series resistor is not efficient in preventing over-programming and an on-chip resistor is more desirable. Poly-silicon bottom electrode based devices (with the poly-silicon electrode acting like an on-chip resistor) and metal bottom electrode devices were fabricated and tested. The presence of the on-chip resistor is shown to enhance the endurance of the RRAM device. This technique of including an on-chip resistor prevents stored current discharge through the device as the device transitions from a high resistance to a low resistance state. A SPICE simulation is also employed to illustrate the benefit of this approach.
3 citations