Transfer-printed thin film metal electrodes for high-performance ferroelectric P(VDF-TrFE) devices

Electrodes formation method has been found to be very important in electronic devices using ferroelectric P(VDF-TrFE) copolymer. Depending on the deposition system used, vacuum-based deposition methods such as e-beam or thermal evaporation of metal electrodes has resulted in the performance deterioration, due to damages on the fragile organic surface by highly energetic particles such as intensive short-wavelength radiation, secondary electrons, etc. On the other hand, the transfer-printing of electrodes, which is formed on other substrates, onto the organic surface does not involve any such damages, leading to high-performance devices. Further, the transfer-printing process allows additional advantages of electrode surface tailoring or device fabrication on non-flat micro-rough surfaces. The proposed technique has led to much better performance of InGaZnO-based non-volatile memory transistors, compared to devices based on the direct evaporation of metal electrode. Transfer-printing of electrodes, instead of direct vacuum-based deposition, may lead to higher performing devices based on other organic electronic materials.     

Advancements in materials,devices, and integration schemes for a new generation of neuromorphic computers

The slowing pace of performance improvements in modern processors along with the breakdown of power scaling forecasts an imminent end to the traditional transistor scaling roadmap. Additionally, meeting the aggressive demands of proliferating applications in big-data processing, machine learning, artificial intelligence, and highly distributed edge computing requires radical advancements in materials, devices, and architectures for future processors. Neuromorphic computing has emerged as the most promising successor to conventional complementary metal oxide semiconductor (CMOS) devices and von Neumann architecture. This work reviews the status of neuromorphic research, compares the traditional CMOS approach with neuromorphic devices for implementing biologically inspired circuits, and provides an outlook into integration schemes for future brain-inspired computing hardware.     

Trapping properties of sputtered hafnium oxide films: Bulk traps vs. interface traps

The purpose of this work is to investigate the influence of the spatial distribution of traps on the electrical characteristics of hafnium oxide films deposited by physical vapor deposition. Samples were Al gated metal-oxide-semiconductor capacitors with hafnium oxide films deposited on SiO₂ layer thermally grown on Si. During capacitance-voltage measurements large hysteresis, up to 10 V, are observed in all samples. It is shown that depending on the hafnium oxide deposition conditions, the spatial distribution of the traps responsible for the hysteresis can be either two dimensional (interface/border traps) or three dimensional (bulk traps).     

Ceph分布式存储系统性能优化技术研究综述

Ceph是一个统一的分布式存储系统,可同时提供块、文件和对象3种接口的存储服务。与传统的分布式存储系统不同,它采用了无中心节点的元数据管理方式,因此具有良好的扩展性和线性增长的性能。经过十余年的发展,Ceph已被广泛地应用于云计算和大数据存储系统。作为云计算的底层平台,Ceph除了提供虚拟机的存储服务外,还可以直接提供对象存储服务和NAS文件服务。Ceph支撑着云计算系统中多种操作系统和应用的存储需求,它的性能对其上的虚拟机和应用有较大的影响,因此Ceph存储系统的性能优化一直是学术界和工业界的研究热点。文中首先介绍了Ceph的架构和特性;然后针对现有的性能优化技术,从对内部机制进行改进、面向新型硬件和基于应用的优化这3个方面进行了归纳和总结,综述了近年来Ceph存储和优化的相关研究;最后对该领域未来的工作进行了展望,以期为分布式存储系统性能优化的研究者提供有价值的参考。     

Charge storage characteristics of Au nanocrystal memory improved by the oxygen vacancy-reduced HfO2 blocking layer

This study characterizes the charge storage characteristics of metal/HfO₂/Au nanocrystals (NCs)/SiO₂/Si and significantly improves memory performance and retention time by annealing the HfO₂ blocking layer in O₂ ambient at 400°C. Experimental evidence shows that the underlying mechanism can be effectively applied to reduce oxygen vacancy and suppress unwanted electron trap-assisted tunneling. A memory window of 1 V at an applied sweeping voltage of ±2 V is also shown. The low program/erase voltage (±2 V) and the promising retention performances indicate the potential application of NCs in low-voltage, non-volatile memory devices.     

掺假留兰香原油的鉴别

本文介绍了几种方法,利用简单设备、常用试剂对掺有动物油、植物油、矿物油、水溶性物质和其它掺假物的留兰香原油进行鉴别。     

Science and technology of ferroelectric films and heterostructures for non-volatile ferroelectric memories

We present in this article a review of the status of thin film ferroelectric materials for nonvolatile memories. Key materials issues relevant to the integration of these materials on Si wafers are discussed. The effect of film microstructure and electrode defect chemistry on the ferroelectric properties relevant to a high density nonvolatile memory technology are discussed. The second part of this review focuses on approaches to integrate these capacitor structures on a filled poly-Si plug which is a critical requirement for a high density memory technology. Finally, the use of novel surface probes to study and understand broadband polarization dynamics in ferroelectric thin films is also presented.     

EED: Energy Efficient Disk drive architecture

Energy efficiency has become one of the most important challenges in designing future computing systems, and the storage system is one of the largest energy consumers within them. This paper proposes an Energy Efficient Disk (EED) drive architecture which integrates a relatively small-sized NAND flash memory into a traditional disk drive to explore the impact of the flash memory on the performance and energy consumption of the disk. The EED monitors data access patterns and moves the frequently accessed data from the magnetic disk to the flash memory. Due to the data migration, most of the data accesses can be satisfied with the flash memory, which extends the idle period of the disk drive and enables the disk drive to stay in a low power state for an extended period of time. Because flash memory consumes considerably less energy and the read access is much faster than a magnetic disk, the EED can save significant amounts of energy while reducing the average response time. Real trace driven simulations are employed to validate the proposed disk drive architecture. An energy coefficient, which is the product of the average response time and the average energy consumption, is proposed as a performance metric to measure the EED. The simulation results, along with the energy coefficient, show that the EED can achieve an 89.11% energy consumption reduction and a 2.04% average response time reduction with cello99 trace, a 7.5% energy consumption reduction and a 45.15% average response time reduction with cello96 trace, and a 20.06% energy consumption reduction and a 6.02% average response time reduction with TPC-D trace, respectively. Traditionally, energy conservation and performance improvement are contradictory. The EED strikes a good balance between conserving energy and improving performance.     

基于NVM的存储安全综述

大数据时代的来临为存储系统提供了新的机遇,同时也提出了新的挑战。传统的基于动态随机存储(DRAM)的内存架构面临着容量、能耗、可靠性等方面的问题;新型非易失存储器件(Non-Volatile Memory,NVM)具有非易失、字节寻址、空闲能耗低等优势,可以作为外存、内存或存储级内存(Storage Class Memory,SCM),为未来存储系统的变革提供了新选择,但同时也存在一些安全问题。NVM器件本身的耐久性有限,频繁对某一位置进行写操作时会造成该位置磨损,从而缩短设备的寿命;同时,由于具有非易失性,NVM被用作内存时,断电后数据不会丢失,攻击者可以通过窃取数据来提取敏感信息或对数据进行篡改;当NVM与DRAM构成混合内存时,可能会产生指针指向不明等问题;NVM作为SCM时,应用程序通过存取(load/store)接口直接对其进行访问,绕过了文件系统等权限管理和一致性管理机制。针对这些问题,文中总结了磨损均衡、减少写操作、减少写入量、内存加密、设计一致性机制、设计权限管理机制等解决办法;最后从硬件、操作系统以及编程模型层面探讨了 仍须关注的NVM安全问题。