Jinshi Zhao

Influence of vertex weight on cooperative behavior in a spatial snowdrift game

In this paper the vertex weight is introduced into a snowdrift game to study the evolution of cooperative behavior. Compared with the snowdrift game in a traditional square lattice without any weight, cooperation can be promoted under three types of weight distribution: uniform, exponential and power-law distribution. For an intermediate cost-to-benefit ratio (r), in particular, the facilitation effect of cooperation is obvious. Moreover, the influence of undulation amplitude of weight distribution and the noise strength of strategy selection on cooperative behavior are also investigated. They exhibit a nontrivial phenomenon as a function of r. The results are helpful in analyzing and understanding the emergence of collective cooperation that is found widely in many natural and social systems.

Ultra-Low Power Ni/HfO 2 /TiO x /TiN Resistive Random Access Memory With Sub-30-nA Reset Current

In this letter, we report ultra-low power (sub-30-nA reset current, Ireset) Ni/HfO2/TiOx/TiN RRAM devices that were fabricated with the rapid thermal oxidation of evaporated titanium. RRAM devices show forming-free, bipolar resistive switching behavior, low-resistive state (LRS) nonlinearity, good data retention, and stability. The resistive switching mechanism is mainly attributed to Schottky barrier modulation induced by O2- migration at the Ni/HfO2 interface. LRS/high-resistive state current conduction is controlled by Schottky emission/trap-controlled space-charge-limited current. The TiOx film is believed to provide a local high-density current for the device, confirmed by conductive atomic force microscope results.

Low-Operating-Voltage Resistive Memory Based on Bi1+δFe0.95Zn0.05)O3 Films

A resistive memory device based on the Ag/Bi1+δ(Fe0.95Zn0.05)O₃/SRO/Pt/TiO₂/SiO₂/Si(100) structure was prepared using radio frequency magnetron sputtering. The composition of the thin film element was analyzed by X-ray photoelectron spectroscopy and the thickness of the thin film was characterized by scanning electron microscope. Through the electrical test, we found that the device exhibited low operating voltage, which included VSET of about 0.1 V, VRESET of about -0.1 V, and VF of about 0.25 V. This facilitated the perfect integration of the device with the circuit design. Testing for 10,000 s at a substrate temperature of 85 °C, the device showed excellent retention. The I-V fitting curves of the resistive devices were analyzed. The low resistance state was in line with the ohmic mechanism and the high resistance state was in accordance with the Space Charge Limited Current mechanism. The resistance change of the device was attributed to the formation of Ag conductive filaments.

Plasma assisted fabrication of multi-layer graphene/nickel hybrid film as enhanced micro-supercapacitor electrodes

A facile synthesis strategy has been developed for fabricating multi-layer graphene/nickel hybrid film as micro-supercapacitor electrodes by using plasma enhanced chemical vapor deposition. The as-presented method is advantageous for rapid graphene growth at relatively low temperature of 650 °C. In addition, after pre-treating for the as-deposited nickel film by using argon plasma bombardment, the surface-to-volume ratio of graphene film on the treated nickel substrate is effectively increased by the increasing of surface roughness. This is demonstrated by the characterization results from transmission electron microscopy, scanning electron microscope and atomic force microscopy. Moreover, the electrochemical performance of the resultant graphene/nickel hybrid film as micro-supercapacitor working electrode was investigated by cyclic voltammetry and galvanostatic charge/discharge measurements. It was found that the increase of the surface-to-volume ratio of graphene/nickel hybrid film improved the specific capacitance of 10 times as the working electrode of micro-supercapacitor. Finally, by using comb columnar shadow mask pattern, the micro-supercapacitor full cell device was fabricated. The electrochemical performance measurements of the micro-supercapacitor devices indicate that the method presented in this study provides an effective way to fabricate micro-supercapacitor device with enhanced energy storage property.