Showing papers on "Scanning ion-conductance microscopy published in 2007"

Scanning Electrochemical Microscopy for Direct Imaging of Reaction Rates

Abstract: Not only in electrochemistry but also in biology and in membrane transport, localized processes at solid-liquid or liquid-liquid interfaces play an important role at defect sites, pores, or individual cells, but are difficult to characterize by integral investigation. Scanning electrochemical microscopy is suitable for such investigations. After two decades of development, this method is based on a solid theoretical foundation and a large number of demonstrated applications. It offers the possibility of directly imaging heterogeneous reaction rates and locally modifying substrates by electrochemically generated reagents. The applications range from classical electrochemical problems, such as the investigation of localized corrosion and electrocatalytic reactions in fuel cells, sensor surfaces, biochips, and microstructured analysis systems, to mass transport through synthetic membranes, skin and tissue, as well as intercellular communication processes. Moreover, processes can be studied that occur at liquid surfaces and liquid-liquid interfaces.

Science of Microscopy

Abstract: Imaging With Electrons.- Atomic Resolution Transmission Electron Microscopy.- Scanning Transmission Electron Microscopy.- Scanning Electron Microscopy.- Analytical Electron Microscopy.- High-Speed Electron Microscopy.- In Situ Transmission Electron Microscopy.- Cryoelectron Tomography (CET).- LEEM and SPLEEM.- Photoemission Electron Microscopy (PEEM).- Aberration Correction.- Imaging With Photons.- Two-Photon Excitation Fluorescence Microscopy.- Nanoscale Resolution in Far-Field Fluorescence Microscopy.- Principles and Applications of Zone Plate X-Ray Microscopes.- Near-Field Scanning Probes.- Scanning Probe Microscopy in Materials Science.- Scanning Tunneling Microscopy in Surface Science.- Atomic Force Microscopy in the Life Sciences.- Low-Temperature Scanning Tunneling Microscopy.- Holographic And Lensless Modes.- Electron Holography.- Diffractive (Lensless) Imaging.- The Notion of Resolution.

Scanning electron microscopy of nanoscale chemical patterns.

Abstract: A series of nanoscale chemical patterning methods based on soft and hybrid nanolithographies have been characterized using scanning electron microscopy with corroborating evidence from scanning tunneling microscopy and lateral force microscopy. We demonstrate and discuss the unique advantages of the scanning electron microscope as an analytical tool to image chemical patterns of molecules highly diluted within a host self-assembled monolayer and to distinguish regions of differential mass coverage in patterned self-assembled monolayers. We show that the relative contrast of self-assembled monolayer patterns in scanning electron micrographs depends on the operating primary electron beam voltage, monolayer composition, and monolayer order, suggesting that secondary electron emission and scattering can be used to elucidate chemical patterns.

Invited Review Article: A review of techniques for attaching micro- and nanoparticles to a probe’s tip for surface force and near-field optical measurements

Abstract: Cantilevers with single micro- or nanoparticle probes have been widely used for atomic force microscopy surface force measurements and apertureless scanning near-field optical microscopy applications. In this article, I critically review the particle attachment and modification techniques currently available, to help researchers choose the appropriate techniques for specific applications.

Simultaneous IR material recognition and conductivity mapping by nanoscale near-field microscopy

Abstract: Nanostructures are at the heart of ever-shrinking electronic and photonic devices. The engineering of nanocomposite materials, building blocks, and conduction properties necessitate advanced microscopy tools to assess critical dimensional, compositional, structural, and conduction properties for analysis and quality control. Here we demonstrate with industrial bipolar and metal-oxide-semiconductor (MOS) devices that mid-IR scattering-type near-field optical microscopy (s-SNOM) has the potential to probe all of these parameters, and thereby excels electron and other scanning-probe microscopies. Within a single IR image, all relevant components such as Al, Ti, TiN, Si, Si3N4, and SiO2 are positively identified by material-specific amplitude and phase contrasts in addition to local conductivity in the form of mobile-carrier concentration, here over the range 10–10 cm. We image cross sections of the devices routinely prepared for failure analysis at 30 nm resolution, and this limit could be pushed below 10 nm in the course of future development. Resolution combined with high specificity to material and conductivity properties makes IR s-SNOM a promising tool beyond the microelectronics field for chemical nanotechnology, molecular electronics, photonics, and bioanalytics. IR spectroscopy has tremendous merit in the chemical and structural analyses of materials and in conduction assessment, but until now the limited spatial resolution has prevented its application in industrial failure analysis and quality control. Instead, scanning electron microscopy (SEM) is employed, which offers nanoscale resolution and sensitivity to materials, particularly when combined with Auger, energy-dispersive X-ray (EDX), or wavelength-dispersive X-ray (WDX) spectroscopies. However, only qualitative doping information with decoration-etched samples can be obtained. Transmission electron microscopy (TEM) offers elemental sensitivity in combination with EDX or electron energy loss spectroscopy (EELS), but it suffers from complicated and time-consuming sample preparation. Moreover, the feature sizes of semiconductor structures have already been reduced below the minimum thickness of TEM samples so that details can no longer be imaged. Scanning probe microscopy (SPM) provides topography, and in the extended versions of scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM), also doping but poor material sensitivity. We introduce IR s-SNOM as a method of choice, as SNOM generally extends SPM by the optical near-field interaction between tip and sample, and it thus enables the power of optical spectroscopies, such as fluorescence, Raman, or IR, to be exploited with nanoscale spatial resolution. In particular, IR s-SNOM has a demonstrated specificity to chemical composition, material category, structural variation, and electrical conduction. Our IR s-SNOM technique is based on atomic force microscopy (AFM) as described previously; imaging relies on a commercial, Pt-coated, cantilevered tip operating in tapping mode (frequency X ≈ 30 kHz) with a 20–30 nm radius of curvature. The tip is illuminated by a focused CO2 laser beam at a wavelength k = 10.7 lm. The backscattered light is analyzed interferometrically to record both amplitude and phase. Pure near-field image contrast is attained by pseudoheterodyne interferometric detection at a harmonic frequency nX, with n>1, yielding amplitude sn and phase!n signals simultaneously. According to a point-dipole model, these parameters relate to the complex dielectric value of the sample, e= e1 + ie2. Thus, s-SNOM enables us to distinguish the different materials and doping levels that can be described by a point-dipole model. In this model the field E scattered by the tip is approximated by a dipolar near-field interaction between the tip apex and the sample surface, yielding

A cryogenic Quadraprobe scanning tunneling microscope system with fabrication capability for nanotransport research

Abstract: We describe the development and the capabilities of an advanced system for nanoscale electrical transport studies. This system consists of a low temperature four-probe scanning tunneling microscope (STM) and a high-resolution scanning electron microscope coupled to a molecular-beam epitaxy sample preparation chamber. The four STM probes can be manipulated independently with subnanometer precision, enabling atomic resolution STM imaging and four-point electrical transport study of surface electronic systems and nanostructured materials at temperatures down to 10 K. Additionally, an integrated energy analyzer allows for scanning Auger microscopy to probe chemical species of nanostructures. Some testing results are presented.

Tip dilation and AFM capabilities in the characterization of nanoparticles

Abstract: Scanning-probe microscopy has been routinely employed as a surface characterization technique for more than 20 years. Tip deconvolution, the longest-standing problem associated with particle image analysis in atomic force microscopy (AFM), can be solved by scanning a pre-characterized nanosphere prior to imaging unknown particles.

Dynamic electrochemical-etching technique for tungsten tips suitable for multi-tip scanning tunneling microscopes

Abstract: We present a method to prepare tungsten tips for use in multi-tip scanning tunneling microscopes. The motivation behind the development comes from a requirement to make very long and conical-shape tips with controlling the cone angle. The method is based on a combination of a “drop-off” method and dynamic electrochemical etching, in which the tip is continuously and slowly drawn up from the electrolyte during etching. Its reproducibility was confirmed by scanning electron microscopy. Comparison in tip shape between the dynamic and static methods was shown. [DOI: 10.1380/ejssnt.2007.94]

The study of silver nanoparticles by scanning electron microscopy, energy dispersive X-ray analysis and scanning tunnelling microscopy

Abstract: The authors present results of studies on commercially available silver nanoparticles fabricated by Amepox Microelectronics and delivered in the form of silver powder. The studies were carried out by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and scanning tunnelling microscopy (STM). Chemical analysis performed with the use of EDX revealed that the powder contains about 74% of silver. Further studies of the silver granulate by use of SEM explicitly indicated the presence of micromete-size conglomerates composed of much smaller particles. Silver powder was dissolved in n-hexane, and colloid solution was obtained, in which the particles were subjected to the process of segregation. The colloid, obtained with this method, in which one expected to find particles of smaller sizes, was deposited on the Au(111) surface. The results of the studies of the sample prepared by means of STM enabled us to estimate the distribution of silver nanoparticles size, which appeared to be normal with a relatively small standard deviation.

Bulk Cr tips for scanning tunneling microscopy and spin-polarized scanning tunneling microscopy

Abstract: A simple, reliable method for the preparation of bulk Cr tips for scanning tunneling microscopy (STM) is proposed and its potentialities in performing high-quality and high-resolution STM and spin-polarized STM (SP-STM) are investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to what happens with conventional W tips, rest atoms of the Si(111)-7×7 reconstruction can be routinely observed, probably due to a different electronic structure of the tip apex. SP-STM measurements of the Cr(001) surface showing magnetic contrast are reported. Our results reveal that the peculiar properties of these tips can be suited in a number of STM experimental situations.

Comparison study of live cells by atomic force microscopy, confocal microscopy, and scanning electrochemical microscopy

Abstract: In this report, three kinds of scanning probe microscopy techniques, atomic force microscopy (AFM), confocal microscopy (CM), and scanning electrochemical microscopy (SECM), were used to study live cells in the physiological environment. Two model cell lines, CV-1 and COS-7, were studied. Time-lapse images were obtained with both contact and tapping mode AFM techniques. Cells were more easily scratched or moved by contact mode AFM than by tapping mode AFM. Detailed surface structures such as filamentous structures on the cell membrane can be obtained and easily discerned with tapping mode AFM. The toxicity of ferrocenemethanol (Fc) on live cells was studied by CM in reflection mode by recording the time-lapse images of controlled live cells and live cells with different Fc concentrations. No significant change in the morphology of cells was caused by Fc. Cells were imaged by SECM with Fc as the mediator at a biased potential of 0.35 V (vs. Ag/AgCl with a saturated KCl solution). Cells did not change visib...

Analytical imaging and microscopy techniques.

Abstract: Examination of microorganisms in their natural habitat may be achieved most effectively through the application of a variety of microscope-based techniques. A major goal of the use of microscopic techniques is to achieve minimum disturbance of the system under observation. The major guidelines for all types of laser scanning microscopy (LSM) imaging are to obtain an image using the lowest-intensity laser and the smallest-pinhole aperture to minimize photodamage, optimize image quality (i.e., signal-to-noise ratio), and minimize the thickness of the optical section. Probes useful for fluorescence microscopy may be divided into three different types. Intrinsic probes are already present inside the sample (e.g., pigments such as chlorophyll or phycoerythrins and phycocyanins). Extrinsic probes are those which bind directly to a target (e.g., the general nucleic acid stains, such as 4 ,6 -diamidino-2-phenylindole [DAPI] or the SYTO series). Extrinsic covalently bound probes are usually high-molecular-weight molecules with a high specificity but no fluorescence (e.g., antibodies, lectins, and gene probes). Fluorescence in situ hybridization (FISH) of oligonucleotide probes to specific bacteria has previously been used in conjunction with confocal laser scanning microscopy (CLSM) and epifluorescence microscopy to document microbial diversity in a range of environments, including sewage sludge, river biofilms, and the rhizosphere. A number of emerging microscopy techniques, particularly in fluorescence imaging, may be applied to microbiological samples. These include FLIM, FCS, coherent anti-Stokes Raman scattering (CARS) microscopy, second harmonic imaging microscopy, 4Pi microscopy, stimulated emission depletion microscopy, and near-field scanning optical microscopy (NSOM).

Spherical aberration correction in nonlinear microscopy and optical ablation using a transparent deformable membrane

Abstract: We describe the design and utilization of a deformable membrane to minimize the negative spherical aberration that occurs when a standard water-dipping objective is used to focus within a higher-index sample. In connection with two-photon laser scanning microscopy, we demonstrate twofold improved axial resolution of structures as deep as 1mm in gels and brain tissue. In conjunction with plasma-mediated ablation, we demonstrate enhanced production of optical damage deep within a glass substrate. The present method provides a simple and inexpensive correction for a limited yet important class of optical aberrations.

Scanning probe microscopy study of microcells from the organ surface Bonghan corpuscle

Abstract: Microcells from organ surface Bonghan corpuscles [B. H. Kim, J. Acad. Med. Sci. DPR Kor. 90, 1 (1963)] of mammals have been studied by using optical microscopy, transmission electron microscopy and immunohistochemistry. In order to further investigate their physical and electrical properties at better resolution, many different modes of scanning probe microscopy were used in this research. Their surface morphology was studied by topography imaging and error-signal imaging of atomic force microscopy and their mechanical properties were investigated by force modulation microscopy. Electrostatic force microscopy was also used for their electrical characterization.

Scanning ion conductance microscopy with distance-modulated shear force control

Abstract: A scanning ion conductance microscope (SICM) is based on a tapered nanopipette as a nanoscale conductance probe that is scanned over a sample submerged in an electrolyte solution. In conventional SICM scanning the ion current through the pipette aperture is at the nano- and picoampere level and is influenced by both sample topography and local conductance. Here we present an SICM with integrated shear-force distance control that allows measuring the ion current independently of sample topography. The nanopipette is hereby transversally vibrated and the shear forces that arise are detected optically with the help of two periscopes that are partially submerged in the electrolyte. We also present a new imaging mode designed to facilitate shear-force imaging of soft samples. This mode is based on a periodic modulation of the pipette–sample distance combined with triggered sampling, reducing the probability for sample and pipette damage and increasing the image quality. We apply this imaging mode to polycarbonate membranes and mammalian cells.

Usage of AFM, SEM and TEM for the research of carbon nanotubes

Abstract: This report is focused on a studying of single-walled carbon nanotubes (SWCNTs) by different microscopic methods. It is important for the number of researches to know basic parameters of SWCNTs, especially a diameter and length of one nanotube or a bundle of nanotubes and a number of nanotubes in the bundle. For determination of these parameters Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used.

Scanning ion-conductance microscopy

Abstract: In the present work, the development of a combined specialized scanning ion-conductance microscope (SICM) and fluorescence microscope for non-invasive topographical and optical studies on soft samples immersed in electrolyte solution is reported. In SICM, the scanning probe is an electrolyte-filled glass-nanopipette with a tip aperture diameter of about 50 nanometers. Conductivity of an ionic current through the tip, driven by electrodes inside and outside of the pipette, depends on the distance between tip and sample surface (topographical mapping) and on the sample's chemical properties (chemical mapping). For enhancing the sensitivity of the microscope, it is operated in alternating current mode by applying an oscillation to the probe and using a lock-in detection of the modulated current as feedback signal. The presented combination of scanning ion-conductance and fluorescence microscopy demonstrates parallel acquisition of correlated topographical and chemical or optical information. Characterization of the microscope's properties is presented with a detailed analysis of the interaction of all essential elements participating in its operation. Conceptual design and implementation of the control-software that operates on the instrument's specialized real-time hardware is described. Successful employment of the SICM at a resolution beyond the Rayleigh criterion combined with fluorescence-optical studies is presented, demonstrating the manifold capabilities of this instrument for applications in the interacting fields of physics, biology, and chemistry.

Single-step electrochemical method for producing very sharp Au scanning tunneling microscopy tips.

Abstract: A single-step electrochemical method for making sharp gold scanning tunneling microscopy tips is described. 3.0M NaCl in 1% perchloric acid is compared to several previously reported etchants. The addition of perchloric acid to sodium chloride solutions drastically shortens etching times and is shown by transmission electron microscopy to produce very sharp tips with a mean radius of curvature of 15 nm.

Combined scanning force microscopy and scanning tunneling spectroscopy of an electronic nanocircuit at very low temperature

Abstract: The authors demonstrate the combination of scanning force microscopy and scanning tunneling spectroscopy in a local probe microscope operating at very low temperature (60mK). This local probe uses a quartz tuning fork ensuring high tunnel junction stability. They performed the spatially resolved spectroscopic study of a superconducting nanocircuit patterned on an insulating substrate. Significant deviations from the theoretical prediction are observed.

Scanning force microscopy three-dimensional modes applied to conductivity measurements through linear-chain organic SAMs

Abstract: We present here a new approach, based on the use of three-dimensional operation modes of scanning force microscopy. The protocol used reveals the advantages of independent but simultaneous data acquisition to discriminate between different interaction regimes and obtain accurate measurements. The procedure is applied to investigate the conducting characteristics of submonolayer linear-chain organic films for which the bare metallic substrate provides an excellent in situ reference for molecular lattice periodicity, film thickness determination and conductivity measurements.

New Technique for Ultra-thin Serial Brain Section Imaging Using Scanning Electron Microscopy

Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007

Fluorocarbon Resist for High‐Speed Scanning Probe Lithography

Abstract: Quick as a flash: High-speed scanning probe lithography in perfluorooctane leads to direct deposition of fluorinated amorphous carbon at velocities in the cm s-1 range. Features as small as 27 nm are fabricated on 100-m2 areas within seconds. The nanoscale patterns are characterized by using photoelectron emission microscopy and secondary ion mass spectrometry.

Variable Pressure and Environmental Scanning Electron Microscopy

Abstract: The use of elevated gas pressures in the sample chamber of a scanning electron microscope (i.e., variable pressure SEM, or VPSEM) together with specialized electron detectors create imaging conditions that allow biological samples to be examined without any preparation. Specific operating conditions of elevated pressures combined with sample cooling (usually restricted to the environmental SEM range) can allow hydrated samples to be maintained in a pristine state for long periods of time. Dynamic processes also can be easily observed. A wider range of detector options and imaging parameters introduce greater complexity to the VPSEM operation than is present in routine SEM. The current instrumentation with field emission electron sources has nanometer-scale beam resolution (approx 1 nm) and low-voltage beam capability (0.1 kV). However, under the more extreme variable pressure conditions, useful biological sample information can be achieved by skilled operators at image resolutions to 2 to 4 nm and with primary electron beam voltages down to 1.0 kV. Imaging relating to electron charge behavior in some biological samples, generally referred to as charge contrast imaging, provides information unique to this VPSEM and environmental SEM that closely relates to luminescence imaged by confocal microscopy.