竖立在晶态金表面上的短单壁碳纳米管

合成和提纯了单壁碳纳米管（ＳＷＣＮＴＳ）,用胶体将其竖直地组装在金薄膜表面上,用此组装制造了扫描隧道显微镜（ＳＴＭ）的针尖,成功地观测金晶粒的形貌像和高定向石墨的原子像,ＳＷＣＮＴＳ竖立在金表面上对于电学特性测量,制造场发射电子源,组装纲伙电子器件,制作扫描探针显微镜（ＳＰＭ）针尖等有重要意义。     

STM碳纳米管针尖的研究

合成和提纯了单壁碳纳米管（SWCNTs)。使用水溶胶体,SWCNTs被组装在钨（W）针尖上,它可以用作扫描隧道显微镜（STM）的针尖,得到高定向石墨（HOPG）和金（Au)膜表面的原子分辨像,用场发射显微镜（FEM）研究了SWCNTs的场发射特性,得到了原子分辨的场发射图,与计算的（9,9）扶手椅型的SWCNT结构相一致,研究了SWCNTs的电学特性,观察到了负阻特性。     

扫描隧道显微镜钨针尖氧化层去除的化学方法

电化学腐蚀得到的扫描隧道显微镜(STM)钨针尖表面通常覆盖了一层钨的氧化膜,这层氧化膜的存在很大程度上影响了STM扫描图像质量.本实验采用氢氟酸对新制备出的钨针尖进行去氧化层处理,并通过对比两组高序热解石墨(HOPG)STM图像和金样品的扫描隧道谱来论证这种去氧化层手段的有效性.     

基于自相关的AFM快速成像

原子力显微镜(AFM)的原理是利用针尖与样品表面原子间的微弱作用力来作为反馈信号,维持针尖——样品间作用力恒定,同时针尖在样品表面扫描,从而得知样品表面的高低起伏。然而,原子力显微镜得到的数据是一维的,如何从这一维的数据恢复出被扫描样本的二维图像是一个值得关心的问题。本文主要通过以自相关为核心的相关算法,以Labview为平台,快速从得到的一维数据恢复出被扫描样品的二维图像,从而为进一步的研究提供了便利。同时扩展该算法的用途以作为一种简易滤波器。     

升高模式扫描电容显微镜

分析了升高模式扫描电容显微镜（LM-SCM）的工作原理，得出了像的对比度正比于样品表面电容梯度分布，且在一定针尖-样品模型下，也可得到样品表面的电容分布。利用LM-SCM研究了金电极的表面电容梯度分布，其横向分辨率优于50nm，显示出其在纳米电子学中的巨大应用前景。     

针尖扫描原子力显微镜的光点跟踪设计

提出了一种用于针尖扫描原子力显微镜(AFM)的光点跟踪设计方案,结构简单,容易实现。设计方案对扫描器的负载能力要求不高,而且能使原子力显微镜实现较大范围的针尖扫描。实验结果表明,采用此光点跟踪设计方案的针尖扫描原子力显微镜能实现最大100μm×100μm范围的扫描,z方向上的误差最大1 nm,能很好地满足大样品扫描的需要。     

扫描隧道显微镜钨针尖的制备与表征

采用直流电化学刻蚀方法制备扫描隧道显微镜钨针尖,研究了电化学刻蚀过程中NaOH溶液浓度、钨丝浸入长度和刻蚀电压对针尖形貌的影响。通过扫描电子显微镜(SEM)测量针尖曲率半径和针尖纵横比值,以表征针尖的尺寸和形状;通过能谱仪(EDS)分析针尖表面成分,以表征表面清洁度;通过场发射显微镜(FEM)得到Fowler-Nordheim (F-N)曲线来检测针尖发射性能。实验结果表明,当溶液浓度为2 mol/L、钨丝浸入长度为4 mm、刻蚀电压为3 V时,可以得到曲率半径约为100 nm、纵横比值为13的针尖,且表面无钨的氧化层。FEM结果显示当对针尖施加500 V的负偏压时,针尖可以稳定发射50 nA量级的电流,且针尖性能具有良好的一致性。     

振动模式扫描极化力显微镜及其应用

振动模式扫描极化力显微镜采用一种新的扫描探针显微成像方式，它可以在极化力介导的非接触方式和轻敲方式之间自由切换。在极化力介导的非接触方式中，极化力叠加在范德华力上，克服了一般的原子力显微镜(AFM)非接触模式中因成像力程太短而不容易稳定的缺点；通过调节针尖的高度，从极化力介导的非接触方式进入到极化力介导的轻敲方式，又能部分消除AFM轻敲模式中毛细力的干扰，还可以用比AFM轻敲模式中最小稳定成像力更小的力进行成像。针尖的高度可以通过调节Asp(Amplitude setpoint)或插入扫描高度参数(lift scan height)来控制，这一方法简单易行。利用这一模式对肢体金颗粒和DNA的高度进行测量，在一定程度上证明了轻敲模式中针尖压力的确会造成柔软生物样品的变形。     

磁力显微镜在钢铁材料磁畴分析中的应用

扫描探针显微镜（SPM）是通过探测针尖与样品间不同的相互作用力而获得表面的不同性质，在扫描探针测量技术上发展起来的磁力显微镜（MFM）主要用于材料表面的磁场力分布。     

压电陶瓷扫描管在纳米加工中的应用

用一圆筒形压电陶瓷作三维微位移器，控制扫描隧道显微镜金属探针，利用场蒸发原理，实现了纳米加工。用Ａｕ，Ｃｕ和Ｎｉ等金属针尖在金表面制作了纳米尺寸的图案，汉字，其中组成这些图案和汉字的每个原子堆的直径约１０－４０ｎｍ，实验表现出非常好的可控性，重复性和稳定性。     

躺在石墨表面上的碳纳米管

用扫描隧道显微镜 ( STM)测试分析了高定向石墨 ( HOPG)表面的碳纳米管 .在大气中室温下获得了碳纳米管原子结构 ,测量了碳管的 I- V特性 .结果表明 ,STM观察到的一般情况下的碳管容易呈簇集状态 ,与透射电镜 ( TEM)观察到的碳纳米管一致 ;在稀释和超声之后 ,STM观察到大量的单根碳管 .作者认为产生这种差别的原因 ,和碳管的疏水亲近效应强弱有关     

Towards nanoreliability of sensors incorporating interfaces between single-walled carbon nanotubes and metals: molecular dynamics simulations and in situ experiments using electron microscopy

In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (SWCNTs) embedded in metal matrices. We conducted experimental pull-out tests of SWCNTs embedded in Pd and found maximum forces in the range F ≈ (10 to 65) nN. These values are in good agreement with forces obtained from molecular dynamics simulations taking into account surface functional groups (SFGs) covalently linked to the SWCNT material. The dominant failure mode in experiment is a SWCNT rupture, which can be explained with the presence of SFGs. For further in depth investigations, we present a tensile actuation test system based on a thermal actuator to perform pull-out tests inside a transmission electron microscope with the objective to obtain in situ images of SWCNT–metal interfaces under mechanical loads at the atomic scale. First experiments confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope.     

Development of a technique for high resolution electron microscopic observation of nano-materials at elevated temperatures

A technique for high resolution transmission electron microscopic (TEM) observation of nano-materials at very high temperatures has been developed. A spirally wound tungsten wire, normally used as the heating element of a high resolution-high temperature-specimen heating holder, was coated with a thin carbon film and the carbon film was used as the substrate of nanometer-sized specimen. The carbon film was securely self-adhered on the heater and the form of the carbon film remained unchanged until the tungsten heater is heated to around 1173 K. Temperature distribution on the carbon film has been measured by observing the sublimation of ZnS particles. Behavior of gold atoms on a surface of gold nano-particles dispersed on the carbon film has been clearly observed at 773 K in a scanning transmission electron microscope (STEM).     

The scanning tunneling microscopy and spectroscopy of GaSb1-xBix films of a few-nanometer thickness grown by molecular beam epitaxy

The ultrahigh vacuum scanning tunneling microscope (STM) was used to characterize the GaSb1-xBix films of a few nanometers thickness grown by the molecular beam epitaxy (MBE) on the GaSb buffer layer of 100 nm with the GaSb (100) sub-strates.The thickness of the GaSb1-xBix layers of the samples are 5 and 10 nm,respectively.For comparison,the GaSb buffer was also characterized and its STM image displays terraces whose surfaces are basically atomically flat and their roughness is generally less than 1 monolayer (ML).The surface of 5 nm GaSb1-xBix film reserves the same terraced morphology as the buffer layer.In contrast,the morphology of the 10 nm GaSb1-xBix film changes to the mound-like island structures with a height of a few MLs.The result implies the growth mode transition from the two-dimensional mode as displayed by the 5 nm film to the Stranski-Krastinov mode as displayed by the 10 nm film.The statistical analysis with the scanning tunneling spectroscopy (STS)measurements indicates that both the incorporation and the inhomogeneity of Bi atoms increase with the thickness of the GaSb1-xBix layer.     

单壁碳纳米管表面增强拉曼散射的新方法

依据碳纳米管独特的力学性能,在银表面直接研磨单壁碳纳米管(SWCNTs),在形成纳米级粗糙银表面的同时,SWCNTs管也吸附在银表面上,在银表面粗糙程度和SWCNTs厚度适中的区域得到了高质量的表面增强拉曼散射(SERS)谱。理论分析和实验结果表明,该方法是正确可行的。     

碳纳米管随机网络场效应晶体管电学性能分析

利用电子束蒸发技术在Si衬底形成Au电极作为底栅电极,在底栅电极上生长SiO₂薄膜。超声分散CVD法合成的商用单壁碳纳米管(SWCNTs),使用匀胶机将单壁碳纳米管悬浮液均匀旋涂于SiO₂薄膜上。再利用荫罩式电子束蒸发技术,在单壁碳纳米管随机网络薄膜表面制备漏源电极。该工艺过程避免了碳纳米管过多的化学接触,有效地保护了碳纳米管的性状。在室温条件下对器件电学性能进行测试和分析。使用该方法制备的单壁碳纳米管随机网络薄膜场效应晶体管,具有器件性能稳定、重复性和一致性较好等优点,并可用于构建碳纳米管逻辑电路。该方法对于研究基于碳纳米管的大规模、低成本的集成电路,具有较高的借鉴价值。     

基于单壁碳纳米管可饱和吸收体的被动锁模光纤激光器研究

基于单壁碳纳米管(SWCNTs)作为光学可饱和吸收体(SA)的恢复时间快(<1ps)、饱和光强低、锁模自启动、工作光谱范围宽且制备方法简单、成本低、化学稳定性好、易与光纤兼容等优点,利用SWCNTs-SA实现了稳定脉冲序列输出的实验结果。利用聚甲基丙烯酸甲酯(PMMA)易成膜且机械性能良好的特点,将SWCNTs与PMMA一起分散在二氯化苯(DCB)溶液中,运用光学诱导作用将SWCNTs吸附在单模光纤(SMF)端面,并加热固化成膜。在光纤激光器环形腔结构中引入SWCNT/PMMA薄膜作为SA,获得了具有稳定的重复频率为8.366MHz的基频锁模脉冲序列,其中心波长在1 562nm,脉冲宽度为1.2ps。     

Solid‐State Approach for Fabrication of Photostable,Oxygen‐Doped Carbon Nanotubes

A novel procedure for effective fabrication of photostable oxygen‐doped single‐walled carbon nanotubes (SWCNTs) in solid‐state matrices has been developed. SWCNTs drop‐cast on various types of substrates are coated with oxide dielectric thin films by electron‐beam evaporation. Single tube photoluminescence spectroscopy studies performed at room and cryogenic temperatures reveal that such thin film‐coated tubes exhibit characteristic spectral features of oxygen‐doped SWCNTs, indicating the oxide thin film coating process leads to oxygen doping of the tubes. It is also found that the doping efficiency can be effectively controlled by the thin film deposition time and by the types of surfactants wrapping the SWCNTs. Moreover, aside from being the doping agent, the oxide thin film also serves as a passivation layer protecting the SWCNTs from the external environment. Comparing the thin film coated SWCNTs with oxygen‐doped tubes prepared via ozonolysis, the former exhibit significantly higher photostability and photoluminescence on‐time. Therefore, this one‐step deposition/oxygen‐doping procedure provides a possible route toward scalable, versatile incorporation of highly photostable oxygen‐doped SWCNTs in novel optical and optoelectronic devices.     

粗糙GaAs(001)表面对In015Ga085As薄膜生长的影响

通过改变衬底降温速率的方法利用分子束外延(MBE)和扫描隧道显微镜(STM)联合系统制备了不同形貌的GaAs(001)表面。采用SPIP软件测量统计和Bauer定则理论分析,研究了粗糙GaAs(001)表面对In015Ga085As薄膜生长的影响。结果表明粗糙GaAs(001)表面存在大量的岛和坑,表面能增加,易于In015Ga085As薄膜层状生长形成平整表面。经计算,面积为100×100 nm2的粗糙GaAs(001)表面相对平坦GaAs(001)表面,其表面能增加了4.6×103 eV,大于生长厚度为15 ML的In015Ga085As薄膜应变能(2.3×103 eV),说明In015Ga085As薄膜在粗糙GaAs(001)表面的外延生长模式为层状生长。