扫描显微探针

 随着１９８２年世界上第一台原子分辨的隧道扫描显微镜（ＳＴＭ）问世,掀起了对物质表面微结构研究的热潮,而且蔓延到表面化学以及生物大分子等领域．同时对ＳＴＭ原理及检测技术的推广,促使了原子力显微镜（ＡＦＭ）、近场光学显微镜（ＳＮＯＭ）的发明．现在,以ＳＴＭ、ＡＦＭ、ＳＮＯＭ为代表的高分辨显微镜已经形成了一类新的显微成像技术──扫描探针显微术（ＳＰＭ）．ＳＰＭ最显著的特点就是采用一个极微小的探针（针尖一般在纳米尺度）,在样品表面极小的距离内移动,同时获得样品表面信息．当这极小的探针与样品表面的相互作用强烈依赖于极小的距离（大约是指数关系）,仪器的稳定性则是获得理想图像的关键.     

扫描探针显微术与纳米科技

 扫描探针显微术（ＳｃａｎｎｉｎｇＰｒｏｂｅＭｉｃｒｏｓｃｏｐｙ,ＳＰＭ）是８０年代初发展起来的一类新型的表面研究新技术,其核心思想是利用探针尖端与表面原子间的不同种类的局域相互作用来测量表面原子结构和电子结构。它的出现使得纳米科技在近十年来得到了突飞猛进的发展。１．扫描探针显微术扫描探针显微术中最早研制成功的是扫描隧道显微镜（ＳｃａｎｎｉｎｇＴｕｎｎｅｌｉｎｇＭｉｃｒｏｓｃｏｐｙ,ＳＴＭ）,它是宾尼和罗雷尔于１９８１年发明的,二人１９８６年因此被授予诺贝尔物理奖。     

扫描隧道显微镜和原子力显微镜

 在微观领域对物质进行观察和研究中,人们发明了各种显微镜。但是光学显微镜由于受到光的波长的限制而无法达到很高的分辨率,Ｘ射线衍射技术则要求观察样品必须是晶体,透射电镜则需要对观察样品进行超薄切片。所有这些要求使人们的观察受到了限制,因此人们开始研制更加先进的显微镜。１９８２年宾尼格、罗雷尔及其同事们成功地研制出世界上第一台扫描隧道显微镜（ＳＴＭ）,导致了显微领域中的一场革命,并在它的基础上研制出一系列的扫描探针显微镜,如原子力显微镜、磁力显微镜和激光力显微镜等。ＳＴＭ的出现使人类第一次可以实时地观测单个原子在物质表面的排列状态和与表面电子行为有关的物理性质和化学性质。     

扫描隧道显微术最新进展与原子搬迁

自从扫描隧道显微镜问世以来，已陆续发展了一系列新型扫描探针显微仪器，如原子力显微镜、磁力显微镜、摩擦力显微镜等等，这些显微仪器不仅能以极高分辨率研究样品表面的形貌和物理化学性质，而且最近几年还被成功地用于操纵单个的原子和分子，文章着重介绍了ＳＴＭ在这方面的进展情况。     

表面微观形貌测量及其参数评定的发展趋势

由于表面加工质量的不断提高，对微观形貌测量技术提出了更高的要求。传统触针式轮廓仪测量具有稳定、可靠、测量动态范围大等优点，但会划伤被测表面；而非接触式形貌测量技术克服了接触式测量易划伤表面的缺点，它主要包括光学散射法、各种光探针法、光学显微干涉法以及采用ＳＥＭ、ＳＴＭ、光子隧道显微镜和原子力显微镜（ＡＦＭ）来探测表面微观形貌的方法。各种测量方法均有其优点和局限性。光学测量方法由于受衍射限制，使其横向分辨率很难提高，在测量大斜率及台阶表面时，测量误差很大。而ＡＦＭ被公认为是一种理想的表面微观形貌测量方法。此外，在表面微观形貌评定方面，国际上正积极探索各种三维评定参数以取代原来的二维参数。     

光子扫描隧道显微镜的光电成像系统研究

本文论述了光子扫描隧道显微镜（ＰＳＴＭ）的显微成像机理、成像规律，针对具体的物理模型进行数值模拟计算，并得到了与实际探测相一致的场分布规律。采用自行研制的光子扫描隧道显微镜（ＰＳＴＭ）的显微实验系统对多种样品进行了表面显微成像研究，获得了关于样品表面三维立体图像信息，通过多种图像处理手段对原始图像进行后期处理，得到了更具视觉效果、更为逼真的样品表面图像。     

近场扫描光学显微镜中一种新的切向力检测系统

在近场扫描光学显微镜（ＮＳＯＭ）［１］中,近场距离控制一般采用切向力控制法。检测切向力有两种方法：光学检测法和非光学检测法。目前普遍采用非光学检测法,基本上是采用压电陶瓷管控制探针和样品的距离。本文提出一种新的切向力检测系统,利用双压电片实现近场距离控制。实验结果表明,检测灵敏度大大提高,扫描力显微（ＳＦＭ）像的分辨率可达纳米量级。     

近场扫描光电显微镜中一种新的切向力检测系统

在近场扫描光学显微镜（ＮＳＯＭ）＾［１］中,近场距离控制一般要用切向力控制法。检测切向力有两种方法：光学检测法和非光学检测法。目前普遍采用非光学检测法,基本上是采用压电陶瓷管控制探针和样品的距离。本文提出一种新的切向力检测系统,利用双压电片实现近场距离控制。实验结果表明,检测灵敏度大大提高,扫描力显微（ＳＦＭ）像的分辨率可达纳米量级。     

扫描力显微镜研究进展

在讨论扫描力显微镜基本原理基础上，详细介绍了近期ＳＦＭ成像模式和技术的发展以及它们在表面研究中的应用。     

STM的同胞兄弟--原子力显微镜(AFM)

介绍了在扫描隧道显微镜（ＳＴＭ）基础上发展起来的原子力显微镜（ＡＦＭ）的工作原理、关键部分、工作模式及其应用。     

Magnetic force microscopy study of magnetic stray-field effects due to mechanical surface modifications of patterned Permalloy thin films

The domain structure of magnetic thin films is strongly influenced by the presence of surface defects. We have used a scanning tunneling microscope for local surface modifications of thin Permalloy films by mechanical interaction between tip and sample. The changes of the magnetic stray-field distribution due to local topographic modifications have been probed by magnetic force microscopy. The relationship between the surface morphology and the micromagnetic structure is studied for different types of surface modifications.     

Magnetic properties of epitaxial Co nanodisk arrays packed on atomically smooth and vicinal Si substrates

Arrays of circular nanodisks have been formed from epitaxial Co films deposited on atomically smooth and vicinal Si(111) single crystals by using a focused Ga⁺ ion beam. The surface roughness has been determined by scanning tunneling microscopy. The coercive force and the processes of magnetization reversal in films and arrays of epitaxial Co nanodisks have been studied. It has been shown that the coercive force of the Co nanodisk arrays on the atomically smooth Si(111) surface is larger and that on the vicinal Si(111) surface is smaller than that in the epitaxial films. The studies of the magnetic structure of the nanodisks by magnetic-force microscopy in combination with the micromagnetic simulation have shown that the processes of magnetization reversal in the nanodisks on the atomically smooth substrates occur through the vortex-like states and, on the vicinal substrates, through the C-type state.     

Formation and characterization of high-density Fe cluster-assembled films with soft magnetic behaviors

High-density, magnetically soft Fe cluster-assembled films were obtained at room temperature by an energetic cluster deposition. Size-monodispersed Fe clusters with the mean cluster size d = 9, 13 and 16 nm were produced using a plasma-gas-condensation technique. Ionized clusters in cluster beam were accelerated electrically and deposited onto the substrate together with neutral clusters from the same cluster source. The morphology, microstructure and magnetic properties of the cluster-assembled films have been studied by an atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and superconducting quantum interference device magnetometer. By increasing the impact energy of the ionized clusters up to 0.6 eV/atom, the Fe cluster-assembled film has a packing fraction of 0.86±0.03, and reveals a soft magnetic behavior. In addition, it is found that oxidization of the cluster-assembled films is remarkably suppressed with the increase in the density of the films.     

Influence of the surface morphology of single-crystal Si(111) substrates on the magnetic properties of epitaxial cobalt films

The epitaxial films Co(111)/Cu(111)-R30°/Si(111) have been grown on the atomically smooth and vicinal Si(111) surfaces. The roughnesses of the substrate and the cobalt film have been determined using scanning tunneling microscopy. The dependence of the coercive force has been investigated as a function of the azimuthal angle. The dependence of the magnetic anisotropy and the coercive force on the surface roughness has been determined. It has been shown that, in the epitaxial cobalt films deposited on the atomically smooth silicon surfaces, crystalline anisotropy of the 〈110〉 type leads to the isotropy of the magnetization reversal processes. The step-induced uniaxial anisotropy has been observed upon deposition on the vicinal surfaces. The films deposited on the atomically smooth surfaces have a complex domain structure.     

Study of Perylenetetracarboxylic Acid Dimethylimide Films by Cyclic Thermal Desorption and Scanning Probe Microscopy

Some results of studying the direct-current (DC) conductivity of perylenetetracarboxylic acid dimethylimide films by cyclic oxygen thermal desorption are presented. The microscopic parameters of hopping electron transport over localized impurity and intrinsic states were determined. The bandgap width and the sign of major current carriers were determined by scanning probe microscopy methods (atomic force microscopy, scanning probe spectroscopy, and photoassisted Kelvin probe force microscopy). The possibility of the application of photoassisted scanning tunneling microscopy for the nanoscale phase analysis of photoconductive films is discussed.     

Nanofabrication of weak links based on scanning force methods

Variable thickness bridges of superconducting Nb thin films have been fabricated for the first time by a combination of conventional photolithography and scanning force nanofabrication methods. The weak link behavior of these superconducting nanobridges was verified by low-temperature transport measurements, in particular by measuring the critical current as a function of an externally applied magnetic field. Future applications of miniaturized weak link structures may include highresolution scanning SQUID microscopes.     

Vector magnetisation measurements on thermally evaporated CoCr multilayers and solid solutions for spintronic applications

Structure, morphology and magnetic properties of thermally evaporated Co/Cr multilayers and of the solid solution obtained by isothermal treatment of the layered samples have been studied to evaluate their potential application as high-coercivity materials for hard spin injectors in spintronic devices such as magnetic tunneling junctions. The thermal treatment was performed in a partial pressure of inert gas to allow interdiffusion of Cr and Co. Structure and composition of the materials, as well as the effects of the annealing treatment, have been investigated by field emission scanning electron microscopy and energy-dispersive X-ray analysis. The magnetic configuration of these films was investigated by magnetic force microscopy. Simultaneous measurements of two mutually perpendicular magnetisation components were performed by means of a vector vibrating sample magnetometer, and showed that the in-plane coercivity can be increased by proper thermal treatment from less than 10 Oe to about 240 Oe. However, annealing may result in a loss of compositional and morphologic homogeneity of the films.     

Effect of the number of iron oxide nanoparticle layers on the magnetic properties of nanocomposite LbL assemblies

Aqueous colloidal suspension of iron oxide nanoparticles has been synthesized. Z-potential of iron oxide nanoparticles stabilized by citric acid was −35±3 mV. Iron oxide nanoparticles have been characterized by the light scattering method and transmission electron microscopy. The polyelectrolyte/iron oxide nanoparticle thin films with different numbers of iron oxide nanoparticle layers have been prepared on the surface of silicon substrates via the layer-by-layer assembly technique. The physical properties and chemical composition of nanocomposite thin films have been studied by atomic force microscopy, magnetic force microscopy, magnetization measurements, Raman spectroscopy. Using the analysis of experimental data it was established, that the magnetic properties of nanocomposite films depended on the number of iron oxide nanoparticle layers, the size of iron oxide nanoparticle aggregates, the distance between aggregates, and the chemical composition of iron oxide nanoparticles embedded into the nanocomposite films. The magnetic permeability of nanocomposite coatings has been calculated. The magnetic permeability values depend on the number of iron oxide nanoparticle layers in nanocomposite film.     

Lattice constants of Langmuir-Blodgett films measured by atomic force microscopy

Langmuir-Blodgett (LB) films are examples of soft organic and related biological samples. Therefore it is essential to make sure that the mechanical scanning process does not disturb the specimen. We describe atomic force microscopy measurements of the lattice constants of Cd arachidate LB films. A lattice constant d_hk is revealed correctly by scanning parallel to the corresponding lattice line [hk]. Scanning in deviating directions enlarges the lattice spacing. The phenomena are explained with a simple model. Previous studies where such artefacts have not been reported are discussed.     

Polymerization of Langmuir–Blodgett films of diacetylenes

Monolayer and multilayer assemblies of Langmuir–Blodgett films of 10–12 pentacosadyinoic acid (12–8 diacetylene) were deposited on flat gold substrates. Micrometre-size features were patterned by polymerization of the films by using standard electron beam lithography. Polymerized areas on a monolayer and bilayer, as well as multilayer films, were examined by scanning electron microscopy, atomic force microscopy and resonant Raman spectroscopy. It was established that polymerized areas on a monolayer and bilayer LB film adhere onto the gold substrate after development. The exposure curve, sensitivity, contrast and resolution of the polymer have been determined by using atomic force microscopy and correlated with the deposition conditions and molecular parameters. Stresses induced in the organic film during polymerization lead to an in-plane buckling of the micrometre-size polymer structure. A simple self-consistent theory was developed to predict critical strain and critical length of buckling. The observed effect of buckling of polymers might open an avenue for a wide range of important practical applications in the area of nanomechanical engineering.