Study of aluminium-modified Ge2Sb2Te5 thin films for the applicability as phase-change storage device material

Electrical and optical studies have been carried out on aluminium-modified Ge₂Sb₂Te₅ thin films to check its applicability as an active material in optical and electrical memory storage devices. Five polycrystalline bulk samples were prepared with compositions: Al_x(Ge₂Sb₂Te₅)_1?x; x = 0, 0.08, 0.14, 0.21, 0.25. Amorphous thin films were deposited from the polycrystalline bulk by thermal evaporation. Temperature-dependent resistance shows the increase in crystallization temperature of Ge–Sb–Te films on aluminium addition. Activation energy for conduction, conductivity, optical band gap, coefficient of refraction and extinction coefficient are studied with respect to Al content in both amorphous and crystalline phases of Ge–Sb–Te alloy films.     

高功率飞秒激光与透明介质的相互作用及其应用

随着飞秒(fs.10-15s)激光近些年来得到迅速发展,飞秒激光已广泛应用于物理、化学反应的动力学过程分析.利用飞秒激光的热效应可以忽略的特点进行超精细加工.利用飞秒激光与透明材料的非线性相互作用,可以实现材料内部有空间选择性的三维光功能微结构.文章重点介绍了飞秒激光与透明介质相互作用的原理,以及在三维超高密度光存储、三锥光功能微结构等方面及应用,国内外相关领域的最新进展,并展望了应用前景.     

Intelligent Fibrous Substrates with Thermal and Dimensional Memories

Binding of polyethylene glycols to any fibrous substrate (such as a natural cellulosic or wool, or synthetic fibers polyester, polyamide or polyolefin) is achieved by in situ network polymerization with polyfunctional resins and acid catalysts. The modified substrates contain crosslinked polyethylene glycols that impart several improved functional properties. Two of these properties (thermal adaptability and reversible shrinkage in the wet and dry states) make it appropriate to categorize the modified fibrous substrates as “intelligent materials”. The thermal and dimensional/shape memories of the substrates are influenced and, hence, controlled by the molecular weight of the polyol, crosslink density, curing conditions to affix the polyol and construction of the fibrous substrate. Verification of these effects has been noted by thermal analysis and infrared thermography (for thermal memories) and by measurement of power generated and work performed during wet shrinkage of appropriate substrates (for shape memories). Numerous potential commercial applications are described and some are being actively pursued. © 1997 John Wiley & Sons, Ltd.     

Forming‐free resistive switching characteristics and improved reliability in sub‐stoichiometric NbNx films

In this study, we demonstrate forming‐free and reliable resistive switching (RS) characteristics by controlling the stoichiometry of niobium nitride (NbN_x) films. Compared to a perfect stoichiometric NbN_x film, a decrease of 6% nitrogen content and an increase of 5% O₂ content are found in the sub‐stoichiometric NbN_x sample (s‐NbN_x), and a structural change for the s‐NbN_x film is observed from X‐ray diffraction results, which results in the possibility of abundant defect generation in the s‐NbN_x film at virgin state. In the RS test, the s‐NbN_x film normally carries out well without initial forming because of the already‐formed conducting filaments; in particular, in the reliability study, the s‐NbN_x film shows more stable dc cycling characteristics for 1000 cycles without any degradation and smaller variations in the operating current and voltage characteristics. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Charge trapping models of resistance switching in organic bistable devices with embedded nanoparticles

We discuss three different models of switching between the high conductivity and low conductivity state in organic bistable devices (OBD) with embedded nanoparticles. All models assume the same basic mechanism: charge trapping and de-trapping in metal nanoparticles. We show trapped charges can both induce an increase or a reduction of the total current depending on device configurations. The influence of energy disorder is investigated.     

Towards engineering in memristors for emerging memory and neuromorphic computing:A review

Resistive random-access memory(RRAM),also known as memristors,having a very simple device structure with two terminals,fulfill almost all of the fundamental requirements of volatile memory,nonvolatile memory,and neuromorphic characteristics.Its memory and neuromorphic behaviors are currently being explored in relation to a range of materials,such as biological materials,perovskites,2D materials,and transition metal oxides.In this review,we discuss the different electrical behaviors exhibited by RRAM devices based on these materials by briefly explaining their corresponding switching mechanisms.We then discuss emergent memory technologies using memristors,together with its potential neuromorphic applications,by elucidating the different material engineering techniques used during device fabrication to improve the memory and neuromorphic performance of devices,in areas such as ION/IOFF ratio,endurance,spike time-dependent plasticity(STDP),and paired-pulse facilitation(PPF),among others.The emulation of essential biological synaptic functions realized in various switching materials,including inorganic metal oxides and new organic materials,as well as diverse device structures such as single-layer and multilayer hetero-structured devices,and crossbar arrays,is analyzed in detail.Finally,we discuss current challenges and future prospects for the development of inorganic and new materials-based memristors.