Simulation of SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling

A three-dimensional finite element model for phase change random access memory （PCRAM） is established for comprehensive electrical and thermal analysis during SET operation. The SET behaviours of the heater addition structure （HS） and the ring-type contact in bottom electrode （RIB） structure are compared with each other. There are two ways to reduce the RESET current, applying a high resistivity interracial layer and building a new device structure. The simulation resuIts indicate that the variation of SET current with different power reduction ways is little. This study takes the RESET and SET operation current into consideration, showing that the RIB structure PCRAM cell is suitable for future devices with high heat efficiency and high-density, due to its high heat efficiency in RESET operation.

In/Pd-Doped SnO2-Based CO Micro-Structure Sensor with High Sensitivity and Quick Response

In/Pd-doped SnO2 is synthesized via a sol-gel method and coated on a silicon substrate with Pt electrodes to fabricate a micro-structure sensor. The sensor can be used to detect CO down to l ppm （the sensitivity is about 3）, and the response time and recovery time are about 5 and 15 s, respectively. Excellent selectivity is also found based on our sensor. These results demonstrate a promising approach to fabricate high-performance CO sensors with high sensitivity and quick response.

Clockwise vs Counter-Clockwise I-V Hysteresis of Point-Contact Metal-Tip/Pr0.7 Ca0.3MnO3/Pt Devices

Metal-tip/Pr0.7Ca0.3MnO3/Pt devices possess two types of I-V hysteresis： clockwise vs counter clockwise depending on the tip materials. The criteria for categorization of these two types of devices can be simply based on whether the Gibbs free energy of oxidation for the metal tip is lower or higher than that of PCMO, respectively. While the clockwise hysteresis can be attributed to electric field induced oxidation/reduction, the counter clockwise hysteresis can be explained by oxygen vacancy migration in an electrical field. Alternating-current conductance spectra also reveal distinct hopping barriers between these two categories of devices at high resistive states.

Air Stability of Cs2CO3：Ag/Ag Cathode for Organic Light-Emitting Diodes

We report the superior stability of the composite Cs2CO3 ：Ag/Ag cathode structure, which can be used in efficient organic light-emitting diodes （OLEDs）. Devices with the Cs2CO3：Ag （1：10, 5nm）/Ag （95nm） cathode show a considerably improved lifetime compared with the control device with the Cs2CO3 （0.5 nm）/Ag （100 nm） cathode. The composite Cs2CO3 ：Ag/Ag film is proved to be stable in the atmosphere. X-ray diffraction （XRD） is applied to analyze the crystalline structure of the Cs2CO3：Ag film, and it is demonstrated that CsAg alloy is formed, leading to the improved stability of the thin film and the devices.

Effect of Poly（Ether Urethane） Introduction on the Performance of Polymer Electrolyte for All-Solid-State Dye-Sensitized Solar Cells

The introduction of poly（ether urethane） （PEUR） into polymer electrolyte based on poly（ethylene oxide）, LiI and I2, has significantly increased the ionic conductivity by nearly two orders of magnitudes. An increment of I3- diffusion coefficient is also observed. All-solid-state dye-sensitized solar cells are constructed using the polymer electrolytes. It was found that PEUR incorporation has a beneficial effect on the enhancement of open circuit voltage VOC by shifting the band edge of TiO2 to a negative value. Scanningelectron microscope images indicate the perfect interfacial contact between the TiO2 electrode and the blend electrolyte.

Influences of Interface States on Resistive Switching Properties of TiOx with Different Electrodes

Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal？insulator-metal （MIM） structures for studying the properties and mechanisms of resistive switching. The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states, which are displayed as ohmic-like or non-ohmic contact. Based on the interface states, the electrical models for MIM devices are analyzed and extracted. The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions. All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.

A Study on Porosity Distribution in Nanoporous TiO2 Photoelectrodes for Output Performance of Dye-Sensitized Solar Cells

Porosity as one of the crucial factors to film morphology affects the overall electrical current-voltage characteristics of dye-sensitized solar cell （DSC）. We search for the short-circuit current density, the open-circuit voltage and the maximum power output as the main functional parameters of DSC closely related to porosity under different film thickness. The theoretical analyses show some exciting results. As porosity changes from 0.41 to 0.75, the short-circuit current density shows the optimal value when the film thickness is 8-10 μm. The open-circuit voltage presents different variation tendencies for the film thicknesses within 1-8 μm and within 10-30 μm. The porosity is near 0.41 and the film thickness is about 10 μm, DSC will have the maximum power output. The theoretical studies also illustrate that given a good porosity distribution, DSC can obtain an excellent short-circuit current characteristic, which agrees well with the experimental results reported in previous literature.