Fabrication and investigation of ferroelectric memristors with various synaptic plasticities

In the post-Moore era, neuromorphic computing has been mainly focused on breaking the von Neumann bottlenecks. Memristors have been proposed as a key part of neuromorphic computing architectures, and can be used to emulate the synaptic plasticities of the human brain. Ferroelectric memristors represent a breakthrough for memristive devices on account of their reliable nonvolatile storage, low write/read latency and tunable conductive states. However, among the reported ferroelectric memristors, the mechanisms of resistive switching are still under debate. In addition, there needs to be more research on emulation of the brain synapses using ferroelectric memristors. Herein, Cu/PbZr_0.52Ti_0.48O₃ (PZT)/Pt ferroelectric memristors have been fabricated. The devices are able to realize the transformation from threshold switching behavior to resistive switching behavior. The synaptic plasticities, including excitatory post-synaptic current, paired-pulse facilitation, paired-pulse depression and spike time-dependent plasticity, have been mimicked by the PZT devices. Furthermore, the mechanisms of PZT devices have been investigated by first-principles calculations based on the interface barrier and conductive filament models. This work may contribute to the application of ferroelectric memristors in neuromorphic computing systems.     

使用SiNx原位淀积方法生长的GaN外延膜中的应力研究

采用低压MOCVD系统,在生长过程中使用SiNx原位淀积的方法产生纳米掩模,并在纳米掩模上进行选区生长和侧向外延制备了GaN外延薄膜.使用拉曼光谱和光荧光的手段对GaN外延膜中的残余应力进行了研究.研究发现,用SiNx原位淀积出纳米掩模后,GaN生长将由二维向三维转变,直到完全合并为止.利用拉曼光谱和光荧光谱分别研究了薄膜中的残余应力,两者符合得很好;这种方法生长出的GaN薄膜的应力分布较传统的侧向外延更加均匀;并且从中发现随着生长过程中SiNx原位淀积时间的增加,生长在其上的GaN外延膜中的残余应力减小.这是因为,随着SiNx原位淀积时间的增加,SiNx纳米掩模的覆盖度也增大.因此侧向外延区的比例增大,残余应力随之减小.     

Electroluminescence of an n-ZnO/p-GaN Heterojunction under Forward and Reverse Biases

Electroluminescent characteristics of n-ZnO/p-GaN heterojunctions under forward and reverse biases are studied. Emissions at 389nm and 57Ohm are observed under forward bias. An unusual emission at 390ram appears under reverse bias, and is attributed to the recombination in the p-GaN side of the heterojunction. The yellow emission peaked at 57Ohm is suppressed under reverse bias. The light intensity exponentially depends on the reverse current. The emission under reverse bias is correlated to tunnelling carrier transport in the heterostructure. Our results also support that the well-known yellow band of GaN comes from the transitions between some near-conduction-band-edge states and deep localized acceptor states.     

Passively Q-Switched Nd:YVO_4 Laser Using a Gold Nanotriangle Saturable Absorber

A passively Q-switched Nd:YVO_4 laser at 1064 nm is demonstrated based on a gold nanotriangle saturable absorber(GNT SA).Under a pump power of 3.82 W,the maximum average output power of 218mW is achieved,corresponding to a slope efficiency of 12.9%.The minimum pulse width is 165ns and the maximum pulse repetition rate is 300kHz at the pump power of 3.48 W.Our results prove that the GNT SA is a promising saturable absorber for near-infrared lasers.     

基于"工程教育专业认证"的高分子材料与工程专业本科专业课程设置探索

工程教育专业认证是提高中国高等教育质量的重要手段和工具,也是专业提升人才培养质量的有效方法.专业课程体系是人才培养的关键环节和实现专业培养目标的核心.本文首先分析了工程教育专业认证对高校工科专业的必要性.其次,总结了专业课程设置的几项原则.最后,通过调研国内17所已经通过专业认证高校的专业课程设置情况,对高分子专业人才...     

气相色谱法测定加热不燃烧再造烟叶中烟碱

建立气相色谱法测定加热不燃烧再造烟叶中烟碱含量的分析方法,在样品中加入4 mL 0.5 mol/L氢氧化钠溶液,使样品中的烟碱在碱性条件下充分游离,采用含正十七碳烷内标的异丙醇溶液对样品振荡萃取2 h,采用气相色谱–氢火焰离子化(GC–FID)法进行定量分析。烟碱的质量浓度在0.10～1.00 mg/mL范围内与烟碱色谱峰面积和内标物色谱峰面积的比值线性关系良好,相关系数大于0.999,方法检出限为0.007 mg/mL,定量限为0.024 mg/mL。样品加标回收率为97.62%～100.29%,测定结果的相对标准偏差为1.08%(n=6)。该方法样品处理简单,安全性好,定量结果准确,适用于加热不燃烧再造烟叶中烟碱的测定。     

使用SiNx原位淀积方法生长的GaN外延膜中的应力研究

采用低压MOCVD系统，在生长过程中使用SiN_x原位淀积的方法产生纳米掩模，并 在纳米掩模上进行选区生长和侧向外延制备了GaN外延薄膜.使用拉曼光谱和光荧光的手段对 GaN外延膜中的残余应力进行了研究.研究发现，用SiN_x原位淀积出纳米掩模后 ，GaN生长将由二维向三维转变，直到完全合并为止.利用拉曼光谱和光荧光谱分别研究了薄 膜中的残余应力，两者符合得很好；这种方法生长出的GaN薄膜的应力分布较传统的侧向外 延更加均匀；并且从中发现随着生长过程中SiN_x原位淀积时间的增加，生长在 其上的GaN外延膜中的残余应力减小.这是因为，随着SiN_x原位淀积时间的增加 ，SiN_x纳米掩模的覆盖度也增大.因此侧向外延区的比例增大，残余应力随之减 小. 关键词： GaN x原位淀积')" href="#">SiN_x原位淀积 拉曼 光荧光 残余应力     

“互联网+”背景下混合式教学在“先进纤维材料”课程中的应用*

“先进纤维材料”是我校高分子材料与工程专业的一门专业课程,在培养高分子材料专业技术人才方面起着重要的作用。在互联网高度发达的今天,将基于Canvas教学平台的混合式教学引入“先进纤维材料”教学过程中,把常规的面对面课堂教学与网络教学的优势充分结合,激发学生对专业知识的学习兴趣,加深对所学内容的理解和记忆。同时,为了将教学内容变得更生动形象,针对每一章节重难点录制微课并在其中插入更加直观的视频动画,上传至Canvas教学平台,供学生在课前对所学内容进行自主学习,提高学生自主学习和个性化学习能力。