Electrostatic force microscopy (EFM) is a widely used scanning-probe technique for the characterization of electronic properties of nanoscale samples without the use of electrical contacts. Here we review the basic principles of EFM, developing a quantitative framework by which EFM measurements of extended nanostructures can be understood. We support our calculations with experimental data of EFM of carbon nanotubes and conducting or insulating electrospun polyaniline-based nanofibers. Furthermore, we explore routes towards extending EFM as a means of non-invasively probing the local electronic density of states of carbon nanotubes.

The results of SPM-based localized electrical examination of precipitation hardened Waspaloy microstructures using Electrostatic Force Microscopy (EFM) and Current-Atomic Force Microscopy (I-AFM) are reported herein. The measurements were conducted on two differently etched specimens with the same initial microstructure. Selective etching by preferentially removing the γ′ or the γ phase resulted in a non-uniform surface topography leaving the less reactive phase standing in relief relative to the depressed phase. The presence of a non-uniform surface topography affected the measured EFM response by causing an inhomogeneous surface voltage distribution. A non-linear tip-surface interaction could have further complicated the measured EFM response by making it non-localized. The EFM phase obeyed a supplementary behavior upon reversing the polarity of the DC bias. Using I-AFM, the tip current was found to be the highest at γ-γ′ interphase boundaries, which was attributed to the relaxation of the lattice atoms in the relief zone formed upon etching.

We report on the Magnetic Resonance Force Microscopy (MRFM) experiments performed on a 50 nm thick permalloy and a combined 20 nm thick permalloy – cobalt film. We studied the evolution of the MRFM spectra as a function of the vertical probe-sample distance and the lateral position as probe was scanned across the permalloy/cobalt interface. Our numerical simulations of the ferromagnetic resonance (FMR) modes excited in the presence of a non-uniform tip field of the cantilever compare well with experimental findings. This work demonstrates the capability of MRFM to perform local FMR spectroscopy of different materials in continuous ferromagnetic films.

Staphylococcus aureus is one of the most frequently isolated bacteria from infected medical implants. S. aureus has the capacity to adhere to the surface of an implant where it forms a biofilm. We used atomic force microscopy to probe binding forces between a fibronectin-coated tip and isolates of S. aureus, which were obtained from either patients with infected prostheses or healthy humans. A unique force-signature was observed for binding events between the tip and the cells. There is a strong distinction (p=0.01) in the binding force-signature observed for S. aureus isolated from the infected vs. healthy populations. This observation suggests a fundamental correlation between nanometer scale binding forces and the clinical outcome of patients with implanted medical devices.

Local electrical property of coincidence site lattice boundaries (CSLBs) in location-controlled silicon islands, which are fabricated using micro-Czochralski process (grain filter), was characterized by scanning spreading resistance microscopy (SSRM) and scanning spreading resistance microscopy (SCM). Some CSLBs found in a silicon island are analyzed as Sigma 3 and Sigma 9 by electron back scattering diffraction pattern. These CSLBs are determined as {111}Sigma 3 and {221}Sigma 9 by referring to previous observation results made by transmission electron microscopy. {111}Sigma3 CSLBs shows no activity for SCM or SSRM; this is consistent with previous prediction that {111}Sigma 3 CSLB is not electrical active. We verified a capability of SCM and SSRM for characterizing local electrical property of coincidence site lattice boundary in silicon.

Using a scanning nonlinear dielectric microscopy (SNDM), we observed two standard Si samples with epitaxial staircase structures, which have known dopant density values calibrated by using secondary ion mass spectroscopy (SIMS). As the result, good quantitative correlation between dopant density values and SNDM signals was obtained without the phenomenon of contrast reversal effect, which is associated with conventional scanning capacitance microscopy (SCM) measurements. Thus, it is expected that SNDM will be an effective method for observing the quantitative measurement of two-dimensional dopant profiling on semiconductor devices.

Nanoindentation using an Atomic Force Microscope (AFM) or a nanoindenter was modelled using Finite Element Analysis (FEA). Force versus indentation depth data were taken for a system consisting of a compliant layer on a stiffer substrate. It was found that the FEA results may be expressed analytically by a simple function that describes the reduced modulus value obtained with Oliver and Pharr's method for any moduli values, thickness of layer or radius of the indenter tip. Initial results obtained by varying the Poisson's ratio of the layer and substrate are also presented.

Fibrous materials are used in a variety of applications due to their relatively high surface area to volume as well as anisotropic behavior. Electrospinning is a popular fabrication method which produces polymer nanofibres with a potentially high molecular alignment. In this work we examine the surface free energy of electrospun polyvinyl-alcohol nanofibres and its relation to molecular ordering using scanning probe microscopy adhesion measurements. Comparisons are made with bulk polymer material to show that a high degree of molecular orientation is present at least at the surface of the polymer nanofibre. As a result, the surface free energy of electrospun polymer nanofibres is greater than that of a bulk polymer. This effect indicates that the electrospinning process is effective at polymer alignment over a variety of experimental parameters.

Molecular electronics devices continue to be pursued as a technology that offers the prospect of scaling device dimensions down to a few nanometers and also promote a practical introduction for high-density memory applications. One of several molecular devices is a cross-bar memory device fabricated by nanoimprint lithography process, which has achieved the production of 30-nm half-pitch patterning. However, today's production procedures such as nanoimprint lithography, optical lithography, and electron-beam lithography, do not allow for the resolution to achieve sub-10-nm line-width structures. Recently we have proposed a double nano-“baumkuchen” (DNB) structure, composed of two thin slices of alternating metal/insulator nano-“baumkuchen” as a lithography-free nano-structure fabrication technology. The DNB has potential application in a high-density memory device, the cross point of which can scale down to ultimately a few nanometers feature sizes because the pattering resolution is determined by the metal-deposition rate, ranging from 0.01 nm/s to the order of 0.1 nm/s. One element of the DNB structure is called a quantum cross (QC) device that consists of two metal nano-ribbons having edge-to-edge configuration. In the area of edge-to-edge QC devices there has been no experimental reports, meanwhile face-to-face devices such as cross-bar devices and spin tunneling devices, have been widely studied both theoretically and experimentally. In our present work, as the first experimental attempt toward the fabrication of QC devices, we have studied gold thin films evaporated on polyethylene naphtalate (PEN) organic films, which can be a candidate of metal/insulator part used for QC devices, by using the atomic force microscope (AFM). Au thin films were thermally evaporated on PEN films in the high vacuum chamber including the film-rolled-up system. The Au thickness was measured by a mechanical method using the stylus surface profiler and an optical method using the diode pumped solid state (DPSS) green laser. Surface morphologies of Au thin films on PEN films were analyzed by the AFM at room temperature. As the thickness of Au films evaporated on PEN films decreases from 20 nm to 5 nm, the AFM surface roughness is reduced from 4.8 nm down to 1.5 nm in the scanning area of 500~500 nm2. The Au grain size is 28.0-4.6 nm for 5-nm-thick Au films and 45.8-5.8 nm for 10-nm-thick Au films, respectively. As a result of the scaling investigation of the surface roughness, the surface roughness of 5-nm-thick Au films is 0.22 nm, corresponding to one atomic size, in the scanning scale of 5 nm. These experimental results indicate that Au thin films on PEN films are suitable as a candidate of metal/insulator(organic films) hybrid materials used for QC devices, and may open up a noble research field to clarify the electric characterization of QC devices using a few atoms or molecules leading to high-density memories.

As the critical design requirements decrease, we need to understand how confinement affects the performance of the materials we use. One example of this occurs with the lubricant used on magnetic recording disks to reduce wear between the disk and head reader during unexpected intermittent contact. Lubricants for use in hard drives need to have sufficient reflow and redistribution properties which are stable in a wide range of temperatures experienced in today's hard drive. Since the material properties of the confined system often differ from the bulk properties, the tools needed to properly investigate these systems need to be developed and understood. In this study, we utilized atomic force microscopy (AFM) techniques, to study the confinement effects on lubricant stability with temperature. Our studies have demonstrated distinct changes in adhesion force with changes in the thickness of the confining substrate layer. As adhesion is a component of friction, these changes in adhesion are directly related to lubricant performance and its ability to reduce wear between disk and reader.

In this study, a well-controlled humidity system is used to enhance the sensitivity of AFM for characterizing surface chemical heterogeneity of patterned self-assembled monolayers (SAMs) and hydrophilic-hydrophobic polymeric brush specimens. Dependence of the AFM friction contrasts on the surface energy differences between the hydrophilic regions and hydrophobic regions of the chemically heterogeneous samples has been investigated as a function of relative humidity (RH). Effects of RH and surface chemistry on tip-sample adhesion are also investigated. Both AFM image contrast and tip-sample adhesion forces between the hydrophilic and hydrophobic regions significantly depend on RH and follow the similar trend as a function of RH. The results clearly demonstrate that, by using proper RH at the tip-sample environment, chemically heterogeneous regions can be distinguished with the AFM.

We discuss the possibilities of analysis of electrically active defects in semiconductors and dielectrics by means of Isothermal Capacitance-Transient Spectroscopy and Isothermal Charge-Transient Spectroscopy, applied on sub-micrometer scale. While the first of them utilizes the relaxation of the depletion layer, caused by emission of trapped charges and requires sufficient conductivity, the second directly integrates the transient current and can be applied also to low-conductivity materials like dielectrics.

We present some results obtained on pentacene thin films. By means of our charge-transient spectrometer we have achieved a resolution of hundreds of electrons but we believe it can be further improved approximately by one order of magnitude. In materials with relatively high defect concentration, using optimal shape of the probe, a resolution on the order of tens of manometers can be achieved. At low defect concentrations, e.g. in device quality silicon, a resolution on the hundred-nm level is expected.

Polymer nanofibres produced by electrospinning techniques have unique mechanical properties due to their large surface area to volume ratio and potentially high molecular orientation. The effects of temperature on mechanical properties is challenging to measure due to the small fibre diameters produced. In this paper, scanning probe microscopy (SPM) is successfully used to elucidate the mechanical performance of individual electrospun polyvinyl alcohol (PVA) nanofibres over a range of temperatures. As observed in the results, thermal transitions have a dramatic effect on the mechanical behaviour of the nanofibres and are highlighted using SPM techniques analogous to dynamic mechanical thermal analysis but at the nanoscale. Interestingly, nanofibre thermal transitions are shown to be mediated by fibre diameter and the driving force of reducing the surface area of the nanofibre.

We have developed an atomic force microscopy (AFM) observation technique with which Si trench sidewall surface can be scanned with the tip of cantilever to investigate its nano-scale morphologies. By developing a new technique of cleaving the substrate at the center of a micron-sized trench along its longitudinal direction [011], the sidewall nano-scale morphology of the trench could be observed with the AFM technique. By comparing of cross sections of the images, we also investigated the difference between Si and carbon nanotube (CNT) tips for the AFM observations. According to the results, the CNT tip proved to show a superior signal-to-noise (S/N) ratio compared with the Si tip. The CNT tip enables us to observe the step patterns of the sidewalls of micron-sized trench structures in the various phases of hydrogen annealing.

Three dimensional scaffolds (3D) are promising for future nanoscale materials and tissue engineering applications being that they have architecture and mechanical properties similar to natural tissue. In this work, poly(lactic acid) fibers were prepared via electrospinnig with average diameters of 2580 nm. Using Enzymatic Surface-Initiated polymerization (ESIP), poly(3-hydroxybutyrate) were coated on poly(lactic acid) fibers. This provides an alternative method to enzymatic surface modification of fibers. ESIP of PHB produces a granular film providing surface topography and increases mechanical properties of PLA fibers alone. When using covalent approaches, PHB granules provide surface topography of 200-500 nm with a polydisperse coverage area. Compressive modulus measurements of PLA and PHB/PLA scaffolds were 25 kPa and 73 kPa, respectively. The percent crystallinity of PLA and PHB/PLA scaffolds was 17% and 30%, respectively. This rough topography, in addition to the crystallinity of the scaffold, facilitates Soas-2 osteoblast cell attachment. We have observed attachment of the osteoblast cells along the length of the oriented PLA and PHB/PLA composite scaffolds with different morphologies, rounded and stretched, throughout a depth of 90 µm.

We show a different method in doing near-field Raman imaging with sub-diffraction limit spatial resolution. A dielectric microsphere (for example polystyrene microsphere) is trapped by optical tweezers. The microsphere is used to focus the laser to the sample, and also to collect the scattered Raman signals. We show the capability of this method in imaging various types of samples, such as SiGe/Si structures, gold nanopattern and carbon nanotubes. This method is comparatively easier to perform, better repeatability, and stronger signal than the normal near-field Raman techniques.

Atomic force microscopy (AFM) is an important tool for high resolution studies in biophysics and mechanical studies directed at biological materials. A strong suit of AFM is its ability to measure hardness/elasticity, nonspecific adhesion or ligand-receptor interactions at the picoNewton scale. Molecular interactions are critical factors in a variety of biological phenomenon; such as the initiation, modulation and termination of DNA replication, transcription, enzyme activity, infection, immune responses, tissue generation, wound healing, cell differentiation, apotopsis and physiological responses from drugs, hormones or toxic agents. Using AFM, scientists can probe and quantify these interactions in their native, liquid environments at physiological pH or perform dynamic experiments in situ by removing or adding ions, solutes and reagents to the sample environment. Bioconjugation chemistry and surface chemistry are crucial because a selective ligand must be immobilized on the tip of an AFM probe so that the AFM can resolve the mechanical force required to separate the ligand and its target. The resulting data can be used to calculate forces of unbinding, derive rate constants and infer structural information about the binding pocket. Biomolecular recognition experiments with AFM can be greatly enhanced through the use of relatively short (~8-10 nm), heterobifunctional, elastic, polyethylene glycol (PEG) linkers to immobilize ligands. Heterobifunctional linkers are used in order to permit their sequential immobilization and bioconjugation, while minimizing undesirable polymerizations or self-conjugation. The linkers have an N-hydroxysuccinimide ester at one end to permit their attachment to aminated silicon or silicon nitride AFM probes. Other reactive functional groups, such as a biotin, maleimide, disulfide, aldehyde, or a photoreactive group reside at the opposite end of the linker to permit the direct or indirect attachment of intact antibodies, Fab fragments, peptides, nucleic acids or other biological entities. The PEG linkers are flexible, so an attached ligand has freedom to diffuse within a defined volume of space and approach the binding site in a thermodynamically favorable manner. PicoTREC, an accessory for the Agilent AFM, uses ligand-PEG modified cantilevers to generate a topography image and a recognition image of biomolecular interactions. As the modified cantilever gently oscillates at defined amplitude, it is scanned across a sample and PicoTREC converts the information derived from ligand-receptor interactions into a high resolution, nanometer-scale map. Consequently, the locations of discrete molecular interactions can be easily determined and compared with a topography image of the sample.

High speed atomic force microscopy (AFM) holds the promise of investigating dynamic systems in real time with single molecule resolution. With the big push towards understanding more complex systems such as cell mechanics or cell-cell and cell-virus interactions, a tool is required that can extract information about these processes in real time in a physiological environment. Atomic force microscopy has been successfully used for investigations of many biological systems and materials in real life conditions, but taking AFM images takes too long to follow many biologically relevant processes. Therefore, attempts have been made to develop high speed AFM by reengineering all the components of an AFM system and much progress has been made. To be useful for investigations of biological systems however, it is often essential to keep imaging forces low in order to get good image quality and not to damage the sample. In this paper we will discuss new small AFM cantilevers we've developed to combine high resonance frequencies for faster imaging with low spring constants for gentle imaging.

The deposition of films and coatings is sometimes influenced by the presence of small amounts of moisture, which can affect the nucleation and growth processes. It is important to understand the behavior of coating materials–especially in semiconductors–in terms of hydrophilicity/hydrophobicity along with adhesion forces. Our technical approach centers on the use of the atomic force microscope (AFM) which was found to be a reliable tool for studying the surface characteristics of materials. In addition to obtaining topographic information, the AFM can also probe attractive or repulsive forces between the tip and the sample surfaces. In this research, a systematic study of the influence of humidity on the adhesion forces between different AFM tips (silicon and silicon nitride) and both hydrophilic and hydrophobic materials (quartz, calcite, mica, graphite) has been conducted using atomic force microscopy. Several force-distance curves measured by the M5 AFM have been gathered at a series of different humidity levels and different locations on the samples. In this paper, measurements of the adhesion force for hydrophobic and hydrophilic materials versus humidity are presented. The results show that the adhesion force on graphite which has hydrophobic character is independent of humidity variation. Results also show that the adhesion force for fused quartz, mica, and calcite which are hydrophilic materials, change dramatically with increasing humidity due to capillary forces. This is in good agreement with theoretical calculations.

The focus of this paper is to investigate the synergistic influence of contact loads, surface stress state and chemical environment on material removal during mechanical stimulation of copper surface. A unique setup is used to generate well characterized stress states on a polished copper specimen. Stressed surface of copper specimen is stimulated using tip of the atomic force microscope (AFM) and material removed during stimulation is measured as a function of contact loads, surface stress state and chemical environment. Measured material removal rates display a complex dependence on contact pressures and in-plane stress state which changes as the pH of chemical environment changes from acidic to basic. A surface material removal mechanism based on a single asperity wear and stress-assisted dissolution is proposed to explain the experimental observations