M_(1—β)(TCNQ):用于可擦式高密度存贮器的信息薄膜材料

利用我们自己开发的新型分子电子材料的光致变色性能可制成可擦写的光盘,它的特点是可用任意波长的激光写入,用热、电或光擦除。已经做到Ag_(1-β)(TCNQ)的写擦循环次数N>1000,反差系数K>50%。利用它的电开关性能则预计可在cm~2的基片上用“5μm平面工艺”制成两种1兆位(MB)存贮器。第一种称为“金属有机存贮器(OMM)”,是全固态的电擦除可编程只读存贮器(E~2 PROM),可做在硅片上并与硅器件兼容;另一种称为“可擦式存取存贮管(EAST)”,是一个特殊的电子管,可用作随机存取存贮器(RAM),用电子束进行信息的写入、读出、擦除。这两种存贮器的存贮密度都可接近于光盘存贮器而存取时间相当于半导体存贮器。它们都不用半导体单晶,没有p-n结;器件面积小、工艺简单。可以认为是分子电子学方面真正有实用价值的一些工作的开端。     

基于溶-凝胶制备工艺的SiO_2基复合相变材料研究综述

相变材料可吸收或释放潜热,从而拥有储能调温潜力。溶-凝胶工艺制备的SiO_2基体可为相变材料提供优良的骨架结构,改善相变材料的泄露问题。总结国内外相关文献,介绍了溶-凝胶制备工艺及SiO_2基复合相变材料的形貌。阐述了SiO_2基体与相变材料间的化学相容性、SiO_2基体对相变材料结晶性能的影响以及SiO_2基复合相变材料的热物性、热循环稳定性和储/放热性能。最后对引入碳纤维/碳纳米管和金属/金属氧化物粒子等功能型材料,以增强其导热性能及光热转化能力的两类增强型SiO_2基复合相变材料进行了概述。     

数字式音像记录用光致变色膜的静态和动态性质

一种新的光致变色络合物M1－β（TCNQ），可作为可擦式光盘的良好存贮媒质。本文对这种薄膜进行了静态和动态测试，并对不同金属比的材料作了比较。已得到的结果为：信噪比约50dB，写入度30dB，擦除度28dB，反复擦除次数＞10。因此近期可望在数字式音像记录方面成为一种实用化材料。     

肉豆蔻酸-十四醇/二氧化硅复合相变材料的制备及性能研究

利用肉豆蔻酸(MA)和十四醇(TD)复合制备出二元共熔混合物作为储能基元,以二氧化硅作为载体材料,采用溶胶-凝胶法制得MA-TD/SiO_2定形复合相变材料。在70℃温度条件下,采用扩散-渗透圈法确定MATD相变材料和正硅酸乙酯(TEOS)的最佳质量配比为1∶2。扫描电镜(SEM)观测发现复合相变材料外观近球形,储能基元被固定到SiO_2多孔网络中;DSC检测结果表明复合相变材料的相变起始温度为23.46℃,相变潜热为83.07kJ/kg;红外光谱(FT-IR)测试结果显示相变材料和SiO_2之间为物理复合,未出现新物质;300次0～60℃冷热循环后MA-TD/SiO_2复合相变材料的失重率仅为0.67%,具有良好的热稳定性。     

(Fe0.5 Co0.5)73.5 Cu1 Mo3 Si13.5 B9合金高温磁性的研究

研究了460～580℃等温退火(30min)后纳米晶(Fe0.5 Co0.5)73.5 Cu1Mo3Si13.5B9合金高温软磁性能.结果表明,在Fe73.5Cu1Mo3Si13.5B9纳米晶合金中用Co取代部分Fe仍可形成双相纳米晶结构,并且可显著提高合金的高温特性.与Fe73.5Cu1Mo3Si13.5B9纳米晶软磁合金相比,其室温μi略有下降,但表征高温磁稳定性的居里温度明显提高,同时磁导率在高温下衰减变缓,从而拓宽了纳米晶软磁材料的高温使用范围.文中初步探讨了用Co取代部分Fe后使高温特性得到改善的机理.     

脂肪酸/SiO_2复合相变材料的制备和性能

以癸酸(CA)、月桂酸(LA)、肉豆蔻酸(MA)和棕榈酸(PA)为相变材料并根据理论公式估算低共熔脂肪酸的组成配比和理论热性能,制备了4组三元低共熔脂肪酸。针对适用于夏炎热地区建筑领域的相变储能材料,选取月桂酸-肉豆蔻酸-棕榈酸(LA-MA-PA)为相变芯材,用溶胶-凝胶法制备了LA-MA-PA/SiO_2复合相变材料,并测试了这种复合相变材料的结构和性能。结果表明:LA-MA-PA具有良好的热稳定性和结构稳定性,可均匀地嵌入到SiO_2多孔网络结构中,且相变芯材与载体复合后无新物质生成。LA-MA-PA/SiO_2球体颗粒光滑饱满,分散性良好其粒径约为3μm,经历100次热循环后脂肪酸没有明显的渗漏。这种复合相变材料的相变温度和潜热分别为29.6℃和91.1 J/g,具有良好的热稳定性。     

溶胶-凝胶法制备脂肪酸/SiO_2复合储能相变材料研究

以SiO_2为担载材料、癸酸-硬脂酸脂肪酸低共熔物为相变芯材,通过溶胶-凝胶法制备脂肪酸/SiO_2复合储能相变材料,并通过SEM,FT-IR,DSC及TG对其结构和性能进行了分析和表征。结果表明:当癸酸-硬脂酸的掺量为55%时,脂肪酸能牢固封存于SiO_2的三维空间网络结构中,复合储能相变材料颗粒均匀,表面光滑圆润;当超过SiO_2负载量时,多余的脂肪酸会暴露于基体表面,造成颗粒团聚、黏结且分散性差;SiO_2作为担载材料与相变芯材之间仅为简单的物理嵌合关系,同时还能提高复合储能相变材料的高温稳定性,使其在150℃以下具有稳定的热性能;复合储能相变材料的相变温度和潜热分别为29.9℃和68.2J/g,适合作为储能蓄热材料应用于低温相变领域。     

具有高分散稳定性的磷酸锆悬浮液的液固相变循环性能

由于纳米颗粒有聚集和沉降的倾向,纳米悬浮液作为一种相变材料,其液固相变循环稳定性与其冷冻/熔化性能一样重要,然而相关研究却很少。本研究将具有高分散稳定性的磷酸锆(ZrP)碟片悬浮液作为一种新型相变材料,并将其冷冻/熔化性能和循环稳定性与水和石墨烯纳米悬浮液进行比较。实验结果表明:所有样品的过冷度随着冷冻/熔化循环次数的增加而减少;在相同次数的冷冻/熔化循环中,ZrP和石墨烯纳米悬浮液的过冷度比水低,且粒子浓度较大的纳米悬浮液过冷度较小。分析表明,ZrP和石墨烯纳米片和冰晶均可诱导纳米悬浮液中的成核。与石墨烯纳米悬浮液相比,ZrP纳米悬浮液的过冷度在粒子质量浓度为0.1%时较大,但在质量浓度为1.0%时较小。比较两种纳米悬浮液经过冷冻/熔化循环后的分散稳定性,结果表明,与石墨烯纳米悬浮液相比,ZrP纳米悬浮液具有更好的液固相变循环稳定性,因而能更有效减小过冷度。     

PTCR铁电陶瓷热疲劳过程中的反常现象

对(Ba1-xPbx)TiO3基PTCR热敏元件进行的热疲劳研究发现:元件的热疲劳特征与热循环温度以及材料的居里温度密切相关.当热循环温度低于材料的居里温度时,元件的室温电阻率随热循环次数的增加而增加;但当热循环温度高于材料的居里点时,元件的室温电阻率在初始热循环阶段出现负增长现象,然后才随循环次数的增加而增加.对不同温度下的热疲劳机理进行了探讨,并提出Bi是提高(Ba1-xPbx)TiO3系热敏元件性能稳定性较为理想的掺杂元素.     

LiNi_(0.5)Mn_(0.5-x)Co_xO_2(0≤x≤0.12)正极材料的制备及其电化学性能

将简单共沉淀与高温固相法相结合制备了LiNi_(0.5)Mn_(0.5-x)Co_xO_2(0x≤0.12)正极材料,使用XRD、SEM、EDS和XPS等手段表征其物相结构、形貌、各元素的含量和价态,根据恒电流充放电和电化学交流阻抗谱表征其电化学性能。结果表明,LiNi_(0.5)Mn_(0.5-x)Co_xO_2正极材料具有a-NaFeO_2型层状结构;成功地将Co引入到材料的晶格内部分替代了Mn;Ni和Mn的价态分别为+2和+4,Co的价态为+3,引入Co使材料出现氧缺失。引入Co可明显改善材料的倍率性能、循环稳定性和低温性能。在2.75~4.35 V和0.2C条件下x=0.12的电极材料其首次放电比容量为180.8 m Ah·g-1,100次循环后容量保持率为92.3%,-20℃的放电比容量为25℃放电比容量的66.3%。     

Ultra-high-density phase-change storage and memory

Phase-change storage is widely used in optical information technologies (DVD, CD-ROM and so on), and recently it has also been considered for non-volatile memory applications. This work reports advances in thermal data recording of phase-change materials. Specifically, we show erasable thermal phase-change recording at a storage density of 3.3 Tb inch(-2), which is three orders of magnitude denser than that currently achievable with commercial optical storage technologies. We demonstrate the concept of a thin-film nanoheater to realize ultra-small heat spots with dimensions of less than 50 nm. Finally, we show in a proof-of-concept demonstration that an individual thin-film heater can write, erase and read the phase of these storage materials at competitive speeds. This work provides important stepping stones for a very-high-density storage or memory technology based on phase-change materials.     

MnBi films for magnetooptic recording

Progress made during the past years in the area of magnetooptic data storage by the computer industry has been most impressive. Many material media and physical phenomena have been developed for this particular application. It now appears that a large capacity (gsim 10^{10}bits) magnetooptic data store possessing major advantages over the conventional recording techniques could be developed. Of the many materials and techniques advanced to date, the use of thin films of MnBi for thermomagnetic writing, erasing, and magnetooptic reading has received particularly intensive study because of the many unique properties of this film medium. In order to provide an assessment of the potential of this medium for optical memory application, we have included in this review the pertinent material physical properties of MnBi; the memory characteristics in regard to read, write, and erase operation; the physical process involved in the writing and erasure by thermomagnetic technique; the technique for detection of written information; and the utilization of this medium for magnetic holographic storage. Emphasis is given to the material properties and physical phenomena, rather than the systems considerations in using MnBi films for optical memory.     

Mechanism of conductance switching: An optical investigation

Electronic conductance switching in devices based on thin films of an organic molecule has been studied. Switching between two conducting states has been induced by voltage pulse, while the states have been probed by optical and electrical measurements simultaneously. In situ optical measurements showed that electroreduction of molecules led to conductance switching and appearance of high-conducting state in the device. We could “write” or “erase” a state by applying electrical pulse and “read” it by measuring electronic absorbance and conductivity. The “write” and “read” processes have been carried out for many cycles to exhibit a correspondence between conductance switching and electrochromism.     

Study on NIR optical rewritable film based on dithienylethene and upconversion nanocrystals

Tm3+ and Yb3+ codoped NaYF4 upconversion (UC) nanoparticles (NPs) with intense ultraviolet (UV) fluorescence were synthesized using a solvothermal approach. NIR optical rewritable film incorporated with the UCNPs and dithienylethene (DTE) were performed for optical storage based on the photochromic reaction of DTE induced by the intense UV from themultiphoton UC fluorescence of NaYF4NPs. The photochromic DTE did not exhibit obvious fatigue after repetitious write/erase cycles using NIR/green irradiation.     

Material science aspects of phase change optical recording

Chalcogenide thin films are used as the recording medium for phase change-type optical memory discs. The films are switched between amorphous and crystalline states using the heat of a focussed laser beam. Large reflectivity differences between amorphous and crystalline states are then used to store and retrieve the information. An active chalcogenide layer for this purpose should have a high optical absorption coefficient (α), and good structural and thermal stability. It should be possible to switch the chalcogenide layer between amorphous and crystalline states repeatedly within a short duration, the optical contrast should be high, and the material must have large cycling capability. Keeping the above requirements in mind, we have carried out systematic investigation of structural, optical and crystallization behaviour of thin films of various compositions of GaGeTe, Sb₂Te₃ and BiSe. These studies have shown that these materials can be good candidates for use as recording media in erasable phase-change optical recording.     

可擦重写光盘记录介质材料及其特性

可擦重写光盘因其能对已写入文件进行改写,因此比只读光盘、一次写入光盘具有更大的灵活性,从而具有很好的应用前景。论述了两种可擦重写光盘记录介质即磁光盘记录介质与相变光盘记录介质的记录机理,并详细阐述了两种记录介质的性能要求。     

Modeling the grating-formation process in thick bacteriorhodopsin films

We model the grating-formation process in bacteriorhodopsin films for the interference of two plane waves. We simulate the temporal dependence of grating recording and readout, and we examine the behavior of the diffraction efficiency with respect to exposure, write and read wavelengths, and film parameters such as initial optical density and lifetime of the upper state. Gratings written in thick bacteriorhodopsin films are generally nonuniform and nonsinusoidal owing to the absorption and saturation properties of the material. The simulations also show that one can often obtain optimization of hologram recording and readout by writing and reading at wavelengths far off the peak of the ground-state absorbance spectrum, especially for films with high values of the peak optical density.     

Study of rapidly solidified Cu–Cr–RE alloys

Electrical engineering materials of Cu–Cr–RE have been made using the technology of rapid solidification, composite green compacts, extrusion and so on. By means of the analysis of optical metallographs, electron microscopy, physical and mechanical properties as well as electrical properties, and the examining of the hardness, softening temperature, etc. the authors selected Cu–Cr–Y alloy, which has excellent comprehensive properties. The authors have also made a deep study of the chromium and yttrium elements, which affect the structure, the recrystallization temperature, the strength at room and high temperature, the resistivity and contact resistance, and have also compared the properties of the Cu–Cr and Cu–Cr–Y alloy. The results show that rapidly solidified technology and added rare–earth elements not only enhance the fine grain boundary strengthening, but also the second phase strengthening. Cu/Cu–Cr–Y composite material improves the thermal stability and thermal endurance, and also maintains a better electrical conductivity and thermal conductivity.     

Study of rapidly solidified Cu–Cr–RE alloys

Electrical engineering materials of Cu–Cr–RE have been made using the technology of rapid solidification, composite green compacts, extrusion and so on. By means of the analysis of optical metallographs, electron microscopy, physical and mechanical properties as well as electrical properties, and the examining of the hardness, softening temperature, etc. the authors selected Cu–Cr–Y alloy, which has excellent comprehensive properties. The authors have also made a deep study of the chromium and yttrium elements, which affect the structure, the recrystallization temperature, the strength at room and high temperature, the resistivity and contact resistance, and have also compared the properties of the Cu–Cr and Cu–Cr–Y alloy. The results show that rapidly solidified technology and added rare-earth elements not only enhance the fine grain boundary strengthening, but also the second phase strengthening. Cu/Cu–Cr–Y composite material improves the thermal stability and thermal endurance, and also maintains a better electrical conductivity and thermal conductivity.     

Floating gate memories reliability

Besides conventional IC failure mechanisms, the floating gate (FG) device reliability is affected by data retention, characteristic of non-volatile memories, and endurance, typical of electrically erasable arrays. The subjects of this work are EPROM and flash EEPROM, the leading and most promising devices among the FG non-volatile memories. The degradation mechanisms observed in programming and erasing steps are investigated. EPROM data retention is associated with intrinsic and defect related charge loss with both electronic and ionic processes involved. Experimental results are presented. The reliability problems associated with repeated write/erase cycles are introduced, and their effects on EEPROM endurance discussed. Finally, a fishbone diagram for data retention is proposed. The complexity of technology and the cell scaling down with increasing chip size impose lower failure rate goals and reliability becomes integrated within the manufacturing process.