浮栅存储器的单粒子辐射效应研究进展

综述了浮栅存储器的单粒子效应国外研究进展,对浮栅存储器控制电路及存储单元的单粒子效应进行详细分析和讨论。指出控制电路是浮栅存储器单粒子效应的关键部件以及重离子轰击使浮栅存储器数据保持特性退化;阐述了浮栅存储单元辐射后可能的电荷损失机制。最后指出纳米晶浮栅存储器具有好的抗辐射能力。     

银纳米颗粒单层膜的组装及其SERS特性研究

用柠檬酸三钠还原硝酸银制备银溶胶,再添加己烷和乙醇,银纳米颗粒会组装在水面上。利用LB拉膜机滑障沿水面压缩银纳米颗粒,使得银纳米颗粒紧密有序地排列在水面上。把这层银纳米颗粒转移到硅衬底上,即得到一种密集排列的银纳米颗粒单层膜SERS基底,采用扫描电子显微镜（SEM）研究该基底的表面形貌,并以罗丹明6G（Rh6G）作为探针分子检测其SERS活性,结果表明,银纳米颗粒具有较好的均一性和聚集度,且Rh6G在该单层膜基底上得到了非常好的SERS效应。     

基于碳纳米管的LB膜制备技术

采用混酸处理法对碳纳米管进行了羧化改性，然后进一步运用十八胺双性分子对羧化改性后的碳纳米管进行了表面修饰，深入探讨了基于双性分子表面改性后碳纳米管的LB膜制备过程，并分析了其制备工艺中超声时间、酸量和氧化处理等实验参数对羧化改性的影响，制备出了基于碳纳米管的单层及多层LB膜。初步研究了硅基底表面碳纳米管LB膜的减摩性能．实验结果表明，带有双性分子的十八胺可通过一定的实验条件连接到碳纳米管表面，通过双性分子的亲油性而有效改善碳纳米管在有机溶剂中的溶解性，为碳纳米管LB膜的制备提供了必要条件；此种碳纳米管LB膜可在低载荷下，将硅基底的耐磨性能提高50％以上．     

一种新型可溶喹吖啶酮衍生物LB膜的制备及其光谱特性

采用表面压-分子面积(π一A)等温曲线和紫外-可见吸收谱的方法研究了一种新型喹吖啶酮衍生物材料LB膜的制备及其光谱特性．实验表明,这种新型喹吖啶酮衍生物能够在水面上形成稳定的单分子膜,它与花生酸(AA)混合后不仅可以形成很好的单分子膜,而且可以较好地转移到固体基片上制备成LB膜多层膜．这种新型喹吖啶酮衍生物LB膜的紫外-可见吸收谱的吸收峰位较稀溶液发生了红移,这是由极性溶剂分子与其相互作用的结果．它在溶液和LB膜中都是以单体的形式存在．     

利用STM制作有机LB膜超高密度存储器

利用有机材料制作高密度存储器是当前纳米电子学研究的一个热点.有机LB膜的有序分子排列和能精确控制厚度的膜层被认为是高密度存储器理想的基体.具有原子分辨率及纳米量级局域作用微区的扫描隧道显微镜(STM)的出现则提供了制作超高密度存储器一种有力的高技术手段.本文介绍利用STM在有机LB膜上制作超高密度存储器.以硬脂酸制备多层LB膜,其形貌由STM成像.施加于STM针尖上的脉冲偏压,在LB膜表面的局域区域产生足够的强电场,使该微区转换为低阻导电状态,以高、低阻态分别表示两种逻辑状态,就完成了一次"写入"操作.LB膜材料的高、低阻态由STM的伏安特性(I-V)和扫描隧道谱(dI/dV-V)加以表征.用幅值较小的脉冲实现"读出"操作.该材料LB膜上存储的信息能保持很长时间,显示了潜在的应用前景.     

膜模拟化学在纳米材料中的应用研究

论述了膜模拟化学在纳米材料中的应用研究,介绍了由表面活性剂或磷脂形成的有序组合体的结构和特征,利用反相胶束,微乳、泡囊,聚离子以及单分子层和多分子层制备了纳米材料,其中包括纳米颗粒,单颗粒膜和无机有机复合膜,评论这些纳米材料的结构和性质。     

导电聚合物有序超薄膜成膜性能的研究

采用LB膜诱导沉积法制备PEDOT高度有序导电聚合物薄膜,采用的工艺是将十八胺(ODA)与聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT-PSS)先形成ODA包裹PEDOT-PSS纳米粒子的组装体,然后再将其铺展于气/液界面,制备PEDOT-PSS复合LB膜。实验表明,PEDOT-PSS纳米粒子对单分子层具有包裹作用,形成了稳定的复合单分子膜;不同膜压下制备的膜表面形貌不同,较高膜压下得到颗粒紧密排列的薄膜,亚相温度23℃、PEDOT-PSS浓度1×10-3mol/L、压缩速率5mm/min、拉膜速率为1mm/min的条件下薄膜具有较好的成膜性能。     

高分子纳米LB膜的制备及其光刻性能研究

合成并表征了N-十六烷基丙烯酰胺（HDA）和对叔丁基苯酚甲基丙烯酸酯（BPhMA）的共聚物p（HDA-BPhMA）s。当HDA含量较高时，共聚物可在气，液界面上形成稳定，排列紧密的单分子薄膜，并可以Y型膜的方式沉积在各种固体基片上，形成多层均匀的Langrnuir-Blodgett（LB）膜。这种LB膜被成功地应用于光刻，获得了分辨率为0.5μm的LB膜图形。以该图形为抗蚀层，可将图形进一步转移至金属薄膜上，得到分辨率较高的金属图形，在图形转移的过程中，这种LB膜显示出较高的抗蚀性，有望作为纳米抗蚀薄膜材料在亚微米刻蚀领域得到应用。     

双层透明耐磨超疏水膜层的制备及界面结构控制

以正硅酸乙酯为前驱体,以溶胶-凝胶法制备的SiO_2溶胶作为黏结剂,首先将SiO_2溶胶在玻璃上旋涂成膜作为底层黏结层,再将亲水型气相SiO_2纳米颗粒与SiO_2溶胶混合后在底层上旋涂成膜作为上层微纳米凹凸膜层,制得双层透明耐磨微纳米凹凸膜层;同时采用KH560嫁接改性的SiO_2纳米颗粒替代未处理的SiO_2纳米颗粒,制得改性双层透明耐磨微纳米凹凸膜层,研究了膜层制备工艺以及SiO_2纳米颗粒改性对膜层界面结构的影响。结果表明,当旋涂转速为400 r/min、膜厚为1.39μm时,底层黏结层具有优异的透光性和耐磨性;紫外臭氧照射20 min后,水接触角为0°,形成高化学活性的亲水性表面。经氟硅烷表面修饰,双层透明耐磨微纳米凹凸膜层和改性双层透明耐磨微纳米凹凸膜层的水接触角分别为151.23°、150.82°,呈现超疏水性;在1 kg/cm~2的荷载作用下,往复打磨200次后,它们的水接触角分别达到121.97°和126.45°,平均面粗糙度保持率高达51.62%和66.33%,下降幅度小,呈现优良的耐磨特性。耐磨特性与界面处的空隙、孔洞密切关联;SiO_2纳米颗粒的改性能够有效地减少界面处的空隙、孔洞,提升膜层的耐磨特性。     

纳米材料制备

【发明名称】一种利用电泳法制备金属/有机多层膜的方法【公开号】1286322【申 请人】中国科学技术大学【摘 要】本发明金属/有机多层膜的制备方法,特征在于先用射线辐照还原含有表面活性剂和OH自由基瘁灭剂的无机盐水溶液制备配位体稳定的金属纳米粒子,再采用电泳法淀积金属/有机多层膜;其金属层为致密、排列有序的单晶或取向膜,质量比现有LB膜的金属层好;本方法采用的原料价廉易得,克服了现有LB技术制备的金属/有机多层膜种类少、金属层不连续的缺点,大大增加了金属/有机多层膜的种类。     

In Situ Self-Assembly of Nanoscale Particles into Macroscale Ordered Monolayers with Enhanced Memory Performance

In situ fabrication of macroscale ordered monolayers of nanoparticles (NPs) on targeted substrates is highly desirable for precision electronic and optical devices, while it remains a great challenge. In this study, a solution is provided to address this challenge by developing a colloidal ink formulation and employing the direct-ink-writing (DIW) technique, where on-demand delivery of ink at a targeted location and directional evaporation with controllable rate are leveraged to precisely guide the deposition of polystyrene-grafted gold NPs (Au@PS NPs) into a macroscale monolayer with an ordered Au NP array embedded in a PS thin film. A 2D steady-state diffusion-controlled evaporation model, which explains the parameter dependence of the experimental results and gives semiquantitative agreement with the experimental evaporation kinetics is proposed. The ordered monolayer is used as both nanocrystal floating gates and the tunneling layer for nonvolatile memory devices. It shows significantly enhanced performance compared with a disordered NP film prepared by spin coating. This approach allows for fine control of NP self-assembly to print macroscaleordered monolayers directly onto substrates, which has great promise for application in broad fields, including microelectronic and photoelectronic devices, sensors, and functional coatings.     

Memory effect of a polymer thin-film transistor with self-assembled gold nanoparticles in the gate dielectric

A self-assembled film of gold nanoparticles is integrated into the gate dielectric of an organic thin-film transistor to produce memory effects. The transistor is fabricated on a heavily doped n-type silicon (n/sup +/-Si) substrate with a thermally grown oxide layer of 100 nm thick. n/sup +/-Si serves as the gate electrode while the oxide layer functions as the gate dielectric. Gold nanoparticles as the floating gate for charge storage are deposited on the gate oxide by electrostatic layer-by-layer self-assembly method. A self-assembled multilayer of polyelectrolytes, together with a thin spin-coated poly(4-vinyl phenol) layer, covers the gold nanoparticles and separates them from the poly(3-hexyl thiophene) channel. Gold nanoparticles are charged or discharged with different gate bias so that the channel conductance is modulated. The memory transistor has an on/off ratio over 1500 and data retention time of about 200 s. The low-temperature solution-based process is especially suitable for plastic-based circuits. Therefore, the results of this study could accelerate achievement of cheap and flexible organic nonvolatile memories.     

A Tunneling Dielectric Layer Free Floating Gate Nonvolatile Memory Employing Type‐I Core–Shell Quantum Dots as Discrete Charge‐Trapping/Tunneling Centers

A nonvolatile memory with a floating gate structure is fabricated using ZnSe@ZnS core–shell quantum dots as discrete charge‐trapping/tunneling centers. Systematical investigation reveals that the spontaneous recovery of the trapped charges in the ZnSe core can be effectively avoided by the type‐I energy band structure of the quantum dots. The surface oleic acid ligand surrounding the quantum dots can also play a role of energy barrier to prevent unintentional charge recovery. The device based on the quantum dots demonstrates a large memory window, stable retention, and good endurance. What is more, integrating charge‐trapping and tunneling components into one quantum dot, which is solution synthesizable and processible, can largely simplify the processing of the floating gate nonvolatile memory. This research reveals the promising application potential of type‐I core–shell nanoparticles as the discrete charge‐trapping/tunneling centers in nonvolatile memory in terms of performance, cost, and flexibility.     

Symmetric Ultrafast Writing and Erasing Speeds in Quasi‐Nonvolatile Memory via van der Waals Heterostructures

Due to the large gap in timescale between volatile memory and nonvolatile memory technologies, quasi‐nonvolatile memory based on 2D materials has become a viable technology for filling the gap. By exploiting the elaborate energy band structure of 2D materials, a quasi‐nonvolatile memory with symmetric ultrafast write‐1 and erase‐0 speeds and long refresh time is reported. Featuring the 2D semifloating gate architecture, an extrinsic p–n junction is used to charge or discharge the floating gate. Owing to the direct injection or recombination of charges from the floating gate electrode, the erasing speed is greatly enhanced to nanosecond timescale. Combined with the ultrafast write‐1 speed, symmetric ultrafast operations on the nanosecond timescale are achieved, which are ≈10⁶ times faster than other memories based on 2D materials. In addition, the refresh time after a write‐1 operation is 219 times longer than that of dynamic random access memory. This performance suggests that quasi‐nonvolatile memory has great potential to decrease power consumption originating from frequent refresh operations, and usher in the next generation of high‐speed and low‐power memory technology.     

Visualization of charges stored in the floating gate of flash memory by scanning nonlinear dielectric microscopy

By applying scanning nonlinear dielectric microscopy (SNDM), we succeeded in clarifying that electrons existed in the poly-Si layer of the floating gate of a flash memory. The charge accumulated in the floating gate can be detected by SNDM as a change in the capacitance of the poly-Si (floating gate) by scanning the surface of the SiO(2)-SiN(4)-SiO(2) (ONO) film covering the floating gate. There was a clear black contrast region in the SNDM image of the floating gate area, where electrons were injected. However, no clear contrast appeared in the floating gate where electrons were not injected. We confirmed that SNDM is one of the most useful methods of observing the charge accumulated in flash memory.     

Silicon nanocrystals synthesized by electron-beam co-evaporation method and their application for nonvolatile memory

In this paper, the silicon nanocrystals (Si NCs)/SiO₂ hybrid films designed for nonvolatile memory applications are prepared by electron-beam co-evaporation of Si and SiO₂. Transmission electron microscopy images and Raman spectra verify the formation of Si NCs. Metal-oxide-semiconductor capacitor structure with Si NCs embedded in the gate oxide is fabricated to characterize the memory behaviors. High-frequency capacitance-voltage and capacitance-time measurements further demonstrate the memory effect of the structure resulting from the charging or discharging behaviors of Si NCs. It is found that the memory window can be changed by adjusting the Si/SiO₂ wt. ratio in source material. The memory devices with Si NCs/SiO₂ hybrid film as floating gate yield good retention characteristics with small charge loss.     

Nonvolatile Perovskite‐Based Photomemory with a Multilevel Memory Behavior

Solution‐processable organic–inorganic hybrid perovskite materials with a wealth of exotic semiconducting properties have appeared as the promising front‐runners for next‐generation electronic devices. Further, regarding its well photoresponsibility, various perovskite‐based photosensing devices are prosperously developed in recent years. However, most exploited devices to date only transiently transduce the optical signals into electrical circuits while under illumination, which necessitates using additional converters to further store the output signals for recording the occurrence of light stimulation. Herein, a nonvolatile perovskite‐based floating‐gate photomemory with a multilevel memory behavior is demonstrated, for which a floating gate comprising a polymer matrix impregnated with perovskite nanoparticles is employed. Owing to the well photoresponsibility introduced by the embedded nanoparticles, the device is enabled to access multiple wavelength response and the functionalities of recording power/time‐dependent illumination under no vertical electrical field. Intriguingly, a nonvolatility of photorecording exceeding three months with a high On/Off current ratio over 10⁴ can be achieved.     

Preparation and characterization of conducting poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Langmuir-Blodgett film

The self-assembly of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) nanoparticles at an air/water interface was achieved by means of the electrostatic force between an octadecylamine (ODA) monolayer and PEDOT-PSS nanoparticles. A surface pressure (π)-area (A) isotherm and X-ray photoelectron spectroscopy of the composite film were used to confirm the electrostatic force between the SO₃⁻ group of PSS and the NH₄⁺ group of aliphatic amines. Monolayer and multilayer composite films of ODA/PEDOT-PSS and ODA-stearic acid (SA)/PEDOT-PSS were fabricated. These solid Langmuir-Blodgett films were investigated by the UV-Vis spectrum, atomic force microscopy, and X-ray diffraction method. It is observed that ODA-SA/PEDOT-PSS films had a higher film-forming capability than ODA/PEDOT-PSS films and an ordered multilayer structure was developed. The conductive properties of ODA-SA/PEDOT-PSS LB films were investigated in detail. Factors influencing the film conductivity such as the layer number and surface pressure were discussed and the conductive mechanism was also studied.     

A Centimeter‐Scale Inorganic Nanoparticle Superlattice Monolayer with Non‐Close‐Packing and its High Performance in Memory Devices

Due to the near‐field coupling effect, non‐close‐packed nanoparticle (NP) assemblies with tunable interparticle distance (d) attract great attention and show huge potential applications in various functional devices, e.g., organic nano‐floating‐gate memory (NFGM) devices. Unfortunately, the fabrication of device‐scale non‐close‐packed 2D NPs material still remains a challenge, limiting its practical applications. Here, a facile yet robust “rapid liquid–liquid interface assembly” strategy is reported to generate a non‐close‐packed AuNP superlattice monolayer (SM) on a centimeter scale for high‐performance pentacene‐based NFGM. The d and hence the surface plasmon resonance spectra of SM can be tailored by adjusting the molecular weight of tethered polymers. Precise control over the d value allows the successful fabrication of photosensitive NFGM devices with highly tunable performances from short‐term memory to nonvolatile data storage. The best performing nonvolatile memory device shows remarkable 8‐level (3‐bit) storage and a memory ratio over 10⁵ even after 10 years compared with traditional devices with a AuNP amorphous monolayer. This work provides a new opportunity to obtain large area 2D NPs materials with non‐close‐packed structure, which is significantly meaningful to microelectronic, photovoltaics devices, and biochemical sensors.     

聚苯乙炔单分子膜成膜特性研究

研究了聚苯乙炔单分子膜的成膜特性及其结构，结果表明，聚苯乙炔能在较大的表面压范围内形成稳定的单分子膜，并具有不可重复压缩性，表面压力的各向异性和松弛特性，ＴＥＭ照片显示，聚苯乙炔分子链在单分子膜中是有序排列的，转移比和ＸＰＳ研究证明，单分子膜向铝片的沉积是成功的。