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.

Recent advances in development of devices and probes for sensing and imaging in the brain

As the most important part of the central nervous system,the brain is extremely complex in structure and function.In vivo analysis of chemical signals is an essential way to investigate brain activity and function.Although functional magnetic resonance imaging(fMRI)or electrophysiology can be used to record brain activity,they are usually limited by low spatiotemporal fidelity or the difficulty of distinguishing the contributions of various neurochemicals.In addition,the development of in vivo biosensors with high selectivity and accuracy is essential to understand the roles that neurochemicals play in the brain.In this review,we focus on the development of instruments and devices for recording chemical signals in the live brain.Meanwhile,the strategies for development of electrochemical and fluorescent probes with high selectivity,high accuracy and good stability are also summarized.In particular,this review highlighted the contributions of our research group to this field.The development of techniques and probes enable us to understand the brain structure and function,and the mechanism of brain diseases,providing the solution for preventing and treating brain diseases.

Analysis of Optical Readout Sensitivity for Uncooled Infrared Detector

An optical readout uncooled infrared detector, employing a substrate-free focal plane array with pitch size 60μm, is established. The reflector deformation induced by the stress mismatching of the bi-layer structure is discussed and, in turn, a universal solution to determine both the optical readout sensitivity and the optimal filter position is found. By applying this solution, the optical readout sensitivity for the ideal plane reflector could theoretically increase by 80% as compared with the conventional operation, and the sensitivity loss caused by the reflector deformation can also be reduced to a reasonable level.

Electromechanical Behavior of Interdigitated SiO2 Cantilever Arrays

Bending and first flexural mode vibration behavior of electrostatic actuated nanometer-sized interdigitated cantilever arrays are characterized under vacuum conditions. The pull-in＇＇ effect in dc driving and the hard spring effect＇＇ in ac driving are observed. A mass sensitivity of 20 fg is expected for our devices due to the ultra-small mass of the arm and relative high Q factor. The mass-spring lump model combined with Green＇s function method is used to fit the dc driving behaviors including the pull-in voltage. For the ac driving case, the polynomial expansion of the capacitive force is used in the model. The successfully fittings of the pull-in voltage and the hard spring effect prove that our simulation method could be used for guiding the geometrical design of cantilever-based sensors.