基于Rotaxane类分子的稳定、重复、可反复擦写的纳米信息存储

Rotaxane类分子在溶液中可以发生可逆的分子构型改变,并随之引起分子电导特性的转变,在纳米电子器件和分子存储器件中具有潜在的应用前景.但是还不能确定这类分子在固体薄膜中是否具有类似于在溶液中的结构与电导转变,需要对Rotaxane类分子固态薄膜进行深入的结构和特性研究.文章作者在一类Rotaxane分子H1和H2的固态薄膜上获得了纳米尺度的电导转变和稳定、重复的、近于单分子尺度的纳米级存储;同时,成功地在H2分子薄膜上实现了信息记录点的可反复擦写.另外,在单个分子和亚分子的水平上直接观察到了Rotax     

纳米电子学中超高密度信息存储研究的新进展

超高密度信息存储是纳米电子学的重要课题，我们根据电荷转移原理，在有机复合薄膜上用扫描隧道显微镜首次得到直径为１３ｎｍ的信息点阵．信息记录点的形成起源于薄膜的局域电导变化，即此有机薄膜具有电学双稳态特性     

有机单体3-phenyl-1-ureidonitrile薄膜的超高密度信息存储

采用扫描隧道显微镜(STM)在3-phenyl-1-ureidonitrile(PUN)有机单体薄膜上进行了超高密度信息存储的研究.通过在STM针尖和高定向裂解石墨(HOPG)衬底之间施加一系列的电压脉冲,在薄膜上写入了一个稳定的5×6信息点阵,信息点的大小是0.8nm.电流电压(I-V)曲线表明,施加电压脉冲前后薄膜的导电性质发生了变化.信息点的写入机制可能是强电场作用下引发的PUN分子的局域聚合,从而导致薄膜由高电阻态向低电阻态转变. 关键词： 超高密度信息存储 有机薄膜 扫描隧道显微镜(STM)     

ULTRAHIGH DATA DENSITY STORAGE WITH SCANNING TUNNELING MICROSCOPY

Ultrahigh density data storage devices made by scanning probe techniques based on various recording media and their corresponding recording mechanisms, have attracted much attention recently, since they ensure a high data density in a non-volatile, erasable form in some kinds of ways. It is of particular interest to employ organic polymers with novel functional properties within a single molecule (or a single molecular complex) for fabricating electronic devices on a single molecular scale. Here, it is reported that a new process for ultrahigh density and erasable data storage, namely, molecular bistability on an organic charge transfer complex of 3-nitrobenzal malononitrile and 1,4-phenylenediamine (NBMN-pDA) switched by a scanning tunneling microscope (STM). Data density exceeds 10¹³ bits/cm² with a writing time per bit of ～1μs. Current-voltage (I/V) measurements before and after the voltage pulse from the STM tip, together with optical absorption spectroscopy and macroscopic four-probe I/V measurements demonstrate that the writing mechanism is conductance transition in the organic complex. This mechanism offers an attractive combination of ultrahigh data density coupled with high speed. The ultimate bit density achievable appears to be limited only by the size of the organic complex, which is less than 1nm in our case, corresponding to 10¹⁴ bits/cm². We believe that provided the lifetime can be improved, molecular bistability may represent a practical route for ultrahigh density data storage devices.     

High quality sub-monolayer,monolayer, and bilayer graphene on Ru（0001）

High quality sub-monolayer, monolayer, and bilayer graphene were grown on Ru(0001). For the sub-monolayer graphene, the size of graphene islands with zigzag edges can be controlled by the dose of ethylene exposure. By increasing the dose of ethylene to 100 Langmuir at a high substrate temperature(800℃), high quality single-crystalline monolayer graphene was synthesized on Ru(0001). High quality bilayer graphene was formed by further increasing the dose of ethylene while reducing the cooling rate to 5℃/min. Raman spectroscopy revealed the vibrational states of graphene, G and 2D peaks appeared only in the bilayer graphene, which demonstrates that it behaves as the intrinsic graphene. Our present work affords methods to produce high quality sub-monolayer, monolayer, and bilayer graphene, both for basic research and applications.     

氢原子吸附对金表面金属酞菁分子的吸附位置、自旋和手征性的调控

实现单个功能有机分子构型、电子结构和自旋态的可逆调控, 是未来分子电子学和分子自旋电子学应用的关键. 近年来, 我们利用极低温强磁场超高真空扫描隧道显微镜系统, 结合第一性原理计算, 系统研究了氢原子吸附对金表面吸附的金属酞菁分子的自旋、手性和吸附位置的调控. 通过将金表面吸附的酞菁锰分子暴露于氢气或氢原子环境, 使得分子中心的磁性离子吸附单个氢原子, 从而实现了体系近藤效应由“开”到“关”的转变. 基于密度泛函理论的第一性原理计算表明, 氢原子吸附使得锰离子3d轨道内的电荷重排导致了分子的自旋由3/2降为1; 同时分子与金基底的间距增大, 使得近藤效应消失. 通过施加局域电压脉冲或者给样品加热, 可以实现单个或所有分子脱氢, 从而恢复体系的自旋态和近藤效应. 氢原子吸附还导致分子的优先吸附位置从金表面的面心立方堆垛区域变成了六角密排堆垛区域. 三个氢原子吸附于同一酞菁锰分子上, 可导致分子对称性的降低及分子镜面对称轴与金基底镜面对称轴的偏离, 从而导致手征性的出现. 这种分子吸附结构的手征性, 导致分子轨道也呈现出手征性. 这项工作为金属酞菁未来在分子电子学、自旋电子学、气体传感器等方面的应用提供了新思路.     

有机纳米信息存储中的结构转变

采用真空热蒸发方法制备了有机单体薄膜对硝基苯腈p-nitrobenzonitrile(PNBN).利用扫描隧道显微镜(STM)在PNBN薄膜上进行信息记录点的写入,通过在STM针尖和高定向裂解石墨(HOPG)之间施加电压脉冲,直接观察到了信息记录点写入前后薄膜发生的局域结构转变.信息记录点的写入机制主要是这种纳米范围结构变化所导致的薄膜由高阻态向低阻态转变,高阻态对应0,低阻态对应1. 关键词： p-nitrobenzonitrile(PNBN) 扫描隧道显微镜(STM) 结构转变     

PIEZOELECTRIC Pb(Zr, Ti)O3 MICRO-DEVICES FOR SCANNING FORCE MICROSCOPY AND ULTRA-DENSITY DATA STORAGE

In this paper we report two types of micro devices based on Pb(Zr, Ti)O₃ (PZT) thin films for improving the throughput of scanning force microscopy (SFM) or data storage using SFM. One is a piezoelectric cantilever array integrated with force sensor as well as z-actuator on each cantilever for parallel operation. The 125-μm-long PZT micro cantilever with a natural resonant frequency of 189 kHz has a high actuation sensitivity of 75 nm/V. Independent parallel images using two cantilevers of the array were obtained. The other is a novel micro-SFM device that is expected to replace the cantilever, the deflection detection unit, and the macro-fabricated scanner which is the bottle neck limiting the single probe acquisition rate. The bridge-structured device has shown a microscopy sensitivity of 0.32 nA/nm in vertical direction and actuation abilities of 70-80nm/±V in the lateral direction.     

低维原子/分子晶体材料的可控生长、物性调控和原理性应用

本文介绍了高鸿钧课题组在物理所20年来的部分代表性工作.研究的主要方向为低维纳米功能材料的分子束外延可控制备、生长机制、物性调控及其在未来信息技术中的原理性应用.从材料的可控制备入手,结合第一性原理的理论计算,阐明材料生长机制和结构与物性的关系,进而实现物性调控和原理性应用.主要内容有:1)纳米尺度"海马"分形结构的形成及其生长机制;2)STM分辨率的提高及最高分辨Si(111)-7×7原子图像的获得;3)固体表面上功能分子的吸附、组装及其机制;4)稳定、重复、可逆的纳米尺度电导转变与超高密度信息存储;5)固体表面上单分子自旋态的量子调控及其原理性应用;6)原子尺度上朗德g因子的空间分辨及其空间分布不均匀性的发现;7)晶圆尺寸、高质量、单晶石墨烯的制备及原位硅插层绝缘化;8)几种新型二维原子晶体材料的可控构筑及其物性调控;9)"自然图案化"的新型二维原子晶体材料及其功能化.这些工作为低维量子结构的构造、物性调控及其原理性应用奠定了基础.     

MLi2H3(M=Na,K)与NH3反应的密度泛函理论研究

采用杂化密度泛函方法,对MLi₂H₃(M=Na, K)团簇与NH₃的反应机理进行计算分析,对反应中各驻点几何构型进行优化,经频率分析和内禀反应坐标计算以确证各驻点的正确性和连接关系.经单点能校正计算,给出反应相关的能量信息.结果表明：引入Na和K原子后,反应物LOMO轨道有大幅度的向Na、K原子处的转移. KLi₂H₃有较小的能隙和电离势及较高的费米能,有较高反应活性. Na、K元素的引入,能破坏反应物的稳定性,降低反应能垒.     

Comparison of tunneling through molecules with Mott-Hubbard and with dimerization gaps

In order to study the tunneling of electrons through an interacting, 1D, dimerized molecule connected to leads, we consider the persistent current in a ring embedding this molecule. We find numerically that, for spinless fermions, a molecule with a gap mostly due to interactions, i.e. a Mott-Hubbard gap, gives rise to a larger persistent current than a molecule with the same gap, but due only to the dimerization. In both cases, the tunneling current decreases exponentially with the size of the molecule, but more slowly in the interacting case. Implications for molecular electronic are briefly discussed. Received: 17 November 1997 / Revised: 16 January 1998 / Accepted: 16 January 1998     

Morphology,miscibility and mechanical properties of PMMA/PC blends

This study deals with some results on morphology, miscibility and mechanical properties for polymethyl methacrylate/polycarbonate (PMMA/PC) polymer blends prepared by solution casting method at different concentration between 0 and 100 wt%. Dynamic storage modulus and tan δ were measured in a temperature range from 30 to 180°C using dynamical mechanical analyzer (DMA). The value of the storage modulus was found to increase with the addition of the PC in the matrix. Transition temperature of pure PMMA and pure PC is found to be 83.8 and 150°C, respectively. The result shows that the two polymers are miscible for whole concentration of PC in PMMA. The distribution of the phases in the blends was studied through scanning electron microscopy (SEM). Also the mechanical properties like elongation at break and fracture energy of the PMMA/PC blends increase with the increase in concentration of PC in PMMA.