Biology Commons^™

Surface Chemical Reactions At The Atomic Scale: Gas Reactions With Semiconductors Studied With Scanning Tunneling Microscopy, R. S. Becker, Y. J. Chabal, G. S. Higashi, A. J. Becker

Scanning Microscopy

The vacuum tunneling microscope has been extensively utilized in the study of the surface atomic configuration of conducting materials. Analysis of features in both the tunneling images and in the tunnel junction I-V characteristic yields insight into a wide variety of processes occurring at surfaces. In the last few years, elementary chemical reactions occurring at surfaces have been examined in this manner, principally adsorption of simple gas species such as H₂, O₂, and NH₃ on semiconductors and metals. Adsorption sites have been deduced from changes brought about in surface configuration subsequent to gas exposure. The …

Recent Developments In Multichannel Raman Microprobing, J. Barbillat, M. Delhaye, E. Da Silva

Scanning Microscopy

This paper reviews the capabilities of multichannel Raman microprobing instruments with emphasis on some major innovative progress recently proposed which looks promising for the development of new fields of application. This new progress includes: confocal Raman microanalysis that provides better spatial resolution and background rejection, confocal Raman mapping that revitalizes the field of Raman imaging pioneered by us 20 years ago, the coupling of molecular Raman microanalysis to elemental electron microprobe, and finally, Raman spectroscopy with near-infrared excitation which permits avoiding the fluorescence limitation of visible Raman spectroscopy.

Anisotropic Secondary Electron Emission From Si(100) Surface Observed By Ultrahigh Vacuum Scanning Electron Microscopy, Yoshikazu Homma

Scanning Microscopy

The effect of surface atomic structure on secondary electron (SE) emission from a Si(100)2 X 1 surface is studied using an ultrahigh vacuum scanning electron microscope with an SE detector having angular resolvability. The double domain structure, alternate 2 X 1 and 1 X 2 domains, can be clearly imaged by SEs, indicating that the SE emission varies with the orientation of dimer rows on Si(100) surface: higher intensity in the direction parallel to the dimer rows and lower intensity in the perpendicular direction. The present results demonstrate that the SE emission is greatly influenced by the atomic configuration in …

Transmission Electron Microscopy And Nanoprobe Analysis Of Ferroelectric Thin Films, Maria Huffman, Mowafak M. Al-Jassim, Chuck Echer

Scanning Microscopy

Thin-film ceramic materials have a variety of electronic applications. Several deposition techniques are currently being used to produce such films with specific properties. For example, rf-sputtered ferroelectric perovskite films, with total thicknesses less than 0.5 μ.m, are being integrated with semiconductor devices as elements for non-volatile memories. Since there is a definite need to characterize these thin films after deposition, electron microscopy has been utilized as one of the most powerful techniques available for examining their morphology and microstructure. Transmission electron microscopy (TEM) examination of these oxides proved difficult. New TEM sample preparation techniques had to be developed in order …

X-Ray Topography, A. Zarka

Scanning Microscopy

The purpose of this paper is to discuss some elements of dynamical theory and to introduce some basic ideas on defect image formation in X-ray topographs. After some explanations of the basic principles of dynamical theory of X-rays, examples of defect contrast are given. Two examples of studies of quartz single crystals by X-ray topography are developed. First, the analysis of the X-ray spherical wave topographs of various Y-cut plates of synthetic quartz crystals show that the coherence of the lattice between the seed and the grown crystal is directly related to the density of the dislocations present in the …

Computation Of Scanning Tunneling Microscope Images Of Nanometer-Sized Objects Physisorbed On Metal Surfaces, J. P. Vigneron, I. Derycke, Th. Laloyaux, Ph. Lambin, A. A. Lucas

Scanning Microscopy

This communication deals with the application of a transfer-matrix strategy for the quantitative evaluation of the tunnel current in a scanning tunneling microscope (STM). The image given by a simple atomic-size object deposited on a metal surface is specifically examined in both modes of STM operation namely the constant-height and the constant-current modes. The two-dimensional corrugation induced at low temperature by Xe atoms physisorbed on an otherwise clean, unreconstructed Ni (110) surface is studied in detail. It is shown that the simple consideration of the elastic scattering of electrons by the three-dimensional potential barrier between the tip and the metal …

Monte Carlo Simulation Of X-Ray Spectra From Rh- And Cu-Targets Generated By Kv-Electrons, K. Araki, Y. Kimura, R. Shimizu

Scanning Microscopy

Monte Carlo simulation is applied to calculate X-ray generation in thick targets under kV electron bombardment. As a preliminary examination, we adopted the simple model based on the uses of: (1) screened Rutherford scattering formula and Bethe's stopping power for describing elastic scattering and energy loss process of penetrating electrons, respectively, (2) Burhop's ionization-cross-section and Sommerfeld's Bremsstrahlung equation for generation of characteristic and continuous X-rays, respectively. In the Monte Carlo simulation, however, more practical expressions were used for convenience of calculation to describe generation of X-rays.

To see how precisely this Monte Carlo simulation describes X-ray spectrum generated in a …

Spectral Decomposition Of Wavelength Dispersive X-Ray Spectra: Implications For Quantitative Analysis In The Electron Probe Microanalyzer, G. Remond, J. L. Campbell, R. H. Packwood, M. Fialin

Scanning Microscopy

The line shapes of Kα, Lα,β and Mα X-ray peaks of pure elements were analyzed by means of commercial wavelength dispersive spectrometers (WDS) attached to an electron probe micro-analyzer (EPMA). A pseudo-Voigt function, i.e., a linear combination of Gaussian and Lorentzian distributions, was used as a fitting profile for the X-ray peaks, with Gaussian offsets incorporated in the short wavelength (high energy) side to describe the observed asymmetry.

The asymmetry of X-ray peaks resulting from both instrumental distortions and satellite bands may lead to discrepancies in quantitative analysis with the EPMA as a function of the procedure used for deriving …

Electron Probe X-Ray Microanalysis Applied To Thin Surface Films And Stratified Specimens, J. L. Pouchou, F. Pichoir

Scanning Microscopy

The basic principles of X-ray microanalysis of thin surface films and stratified targets are summarized. The influence of the electron beam accelerating voltage on the analyzed depth is discussed. It is shown that in the field of soft X-rays, the effective depth of analysis is most often limited by the absorption of the radiation in the specimen itself. For high energy radiations, the importance of the secondary emission due to fluorescence excited by the continuous radiation and by the characteristic lines is outlined. The main concepts of the recent ø(ρz) models used for quantitation in the recent software packages are …

A Few Steps Towards A More Quantitative Understanding Of Contrast In The Scanning Electron Microscope, F. Hasselbach, U. Maier

Scanning Microscopy

The interaction volume of the electron beam with the specimen in a scanning electron microscope (SEM) is a highly complex function of the surface structure of the specimen, its chemical composition and the energy of the scanning electron beam.· The video signals formed by secondary electrons (SE) or backscattered electrons (BSE) reflect this complexity insofar as they may contain not only information of the interior of the pixel which has just been scanned and its neighborhood, but may depend on surface details hundreds of microns apart from the impinging point of the electron beam. This leads to artifacts in scanning …

Applications Of Charge Collection Microscopy: Electron-Beam-Induced Current To Semiconductor Materials And Device Research, Richard J. Matson

Scanning Microscopy

Among all of the possible techniques for the micro-characterization of semiconductor materials and devices in a scanning electron microscope (SEM), charge collection microscopy (CCM), more commonly known as electron-beam-induced current (EBIC), is probably both the most easily deployed and the most versatile characterization technique. Following a brief review of the basic theory of the generation and detection of the EBIC signals, various techniques and applications to the micro-characterization of experimental semiconductor materials and devices will be presented. The applications are primarily to emerging photovoltaic materials and devices. This report is not in any way intended as a complete overview of …

Synchrotron Radiation Induced X-Ray Microanalysis: A Realistic Alternative For Electron- And Ion-Beam Microscopy?, K. Janssens, F. C. Adams, M. L. Rivers, K. W. Jones

Scanning Microscopy

Synchrotron radiation induced X-ray micro fluorescence analysis (μ-SRXRF) is compared with more conventional microanalytical techniques such as secondary ion microscopy (SIMS) and electron probe X-ray microanalysis (EPXMA) for two typical microanalytical applications. μ-SRXRF and EPXMA are employed for the analysis of individual particles, showing the complementary character of both techniques. By means of element mapping of trace constituents in a heterogeneous feldspar material, the strong and weak points of μ-SRXRF in comparison to EPXMA and SIMS are illustrated. The most striking difference between μ-SRXRF and the other two microanalytical methods is the ability of SRXRF to probe deep into the …

Influence Of Primary Electron Beam Angle Of Incidence On Auger Electron Spectra, Mark A. Smith

Scanning Microscopy

A principal step in the extraction of Auger electron yields and line shapes from electron-excited spectra is an understanding of the attendant electron background. Experiments are reported here in which the influence of the primary electron beam angle of incidence on Auger spectral backgrounds has been separated from that of the angle of electron emission. The secondary electron background for clean polycrystalline palladium, on the high-energy side of the MNN peaks, have been studied as functions of primary beam angle of incidence and beam energy. For the range of beam energies investigated, < 10 keV, linearization of the secondary cascade is easily observed in log-log plots of intensity versus energy. When cascades are fitted with Sickafus-type functions, AE^-m (E = electron energy), the parameter m …

Fractal Description Of Electron Scattering In Solids: Several New Results And A Simple Modelization Of The Fractal Dimension, Raynald Gauvin, Dominique Drouin

Scanning Microscopy

The fractal behaviour of electron scattering in solids is studied with electron trajectories simulated by Monte Carlo simulations. More precisely, the Hausdorff-Besicovitch dimension is determined for several electrons trajectories simulated in solids of different compositions. Then, a simple model to compute the fractal dimension of electron trajectories in solids is presented, a model which raises a question concerning the maximum value of the backscattering coefficient. Results of Monte Carlo simulations of electron trajectories in several elements with total randomness for the polar and azimuthal angles of scattering are presented as a tentative answer to this question. Finally, the multi fractal …

Efficiency Of The Secondary Electron Detector In The Scanning Electron Microscope, Zbigniew Czyzewski, David C. Joy

Scanning Microscopy

The efficiency of the secondary electron detector in the scanning electron microscope (SEM) is one of the most important factors affecting the imaging process of the SEM. To compute the detector efficiency, the electrostatic field inside a specimen chamber must be known. A simple way of performing such calculations is to use a spreadsheet program which has a built-in capability of storing and performing some operations on three-dimensional matrices. Using a spreadsheet program makes it possible to solve the Laplace equation and calculate electron trajectories in geometrically complex electrostatic fields. This technique is applied to the estimation of detector efficiency …

Energy Loss Function And Source Function For Au 4f Photoelectrons Derived By Monte Carlo Analysis Of Reflection Electron Energy Loss Spectroscopy (Reels) And X-Ray Photoelectron Spectroscopy (Xps) Spectra, H. Yoshikawa, T. Tsukamoto, R. Shimizu

Scanning Microscopy

We have derived the energy loss function of Au for 1 keV electrons by Monte Carlo analysis of the reflection electron energy loss spectroscopy (REELS) spectra. This energy loss function was significantly different from the optical loss function widely used and has revealed that the surface excitation affects the energy loss spectrum of keV electrons.

X-ray photoelectron spectroscopy (XPS) background subtraction has been recently developed by using the energy loss function derived from the transmission electron energy loss spectroscopy (TEELS). We have demonstrated that the energy loss function derived from REELS has enabled a more accurate Au 4f XPS spectrum …

A Survey Of Electron Probe Microanalysis Using Soft Radiations: Difficulties And Presentation Of A New Computer Program For Wavelength Dispersive Spectrometry, M. Fialin, J. Hénoc, G. Remond

Scanning Microscopy

This paper aims to demonstrate that on-line peak integral technique with wavelength dispersive spectroscopy (WDS) provides accurate results with intensity measurement counting times as short as one or two minutes, owing to the high counting rates obtained with multilayer analyzers. A great advantage of a new computer program using this technique (available on SUN/UNIX work-stations operating Cameca SX-50 microprobes) consists in the original way that peak overlaps are treated. For each analytical point, overlapping counts emerging from an element B (B counts) are removed on-line from the measured raw counts in order to obtain the net counts corresponding to the …

Standardless Quantitative Analysis By X-Ray Spectrometry, János L. Lábár

Scanning Microscopy

Errors in standardless analysis arise from inaccuracies in atomic data, detection efficiency of the detector, the normalization and the sensitivity to the errors of the spectrum processing, and ZAF correction (which converts the ratio of the measured intensities into concentration). Other sources of error encountered in fully quantitative analysis (using standards) also remain in the standardless version. Calculation of the L_α standard intensities also requires incorporation of non-radiative transitions. Both the experimentally found dependence of the net L_α intensities on the atomic number and the corresponding peak-to-background ratios (P/B) indicate that an empirical increase in the …

Contrast Mechanism Of Scanning Tunneling Microscopy: The Two-Sided Point Of View, C. Julian Chen

Scanning Microscopy

It has been known for three decades that tunneling experiments should be explained by the electronic structures of both electrodes. Scanning tunneling microscopy (STM) is no exception. Since the development of STM in the early 1980s, experimental facts have repeatedly shown the necessity to explain the STM images and tunneling spectra from a two-sided point of view. In other words, the STM images and tunneling spectra should be explained by the interaction of the electron density distributions of the tip and the sample (in energy and space). In the early years of STM, due to a scarceness of experimental …

Environmental Scanning Electron Microscope: Some Critical Issues, G. D. Danilatos

Scanning Microscopy

In the environmental scanning electron microscope (ESEM), the gas flow around the main pressure limiting aperture establishes a density gradient through which the electron beam passes. Electron beam losses occur in this transition region and in the uniform gas layer above the specimen surface. In the oligo-scattering regime, the electron distribution consists of a widely scattered fraction of electrons surrounding an intact focussed probe. Secondary electrons are multiplied by means of gaseous ionization and detected both by the ionization current and the accompanying gaseous scintillation. The distribution of secondary electrons is governed by the applied external electric and magnetic fields …

The Nfiii/Oct-1 Binding Site Stimulates Adenovirus Dna Replication In Vivo And Is Functionally Redundant With Adjacent Sequences, Lianna K. Etchberger, P. Hearing

Biology Faculty Publications

The inverted terminal repeat (ITR) of adenovirus type 5 (Ad5) is 103 bp in length and contains the origin of DNA replication. Cellular transcription factors NFI/CTF and NFIII/OCT-1 bind to sites within the ITR and participate in the initiation of viral DNA replication in vitro. The ITR also contains multiple copies of two conserved sequence motifs that bind the cellular transcription factors SP1 and ATF. We have analyzed a series of viruses that carry deletions at the left terminus of Ad5. A virus carrying a deletion of the NFIII/OCT-1, SP1, and ATF sites within the ITR (mutant dl309-44/107) was wild …

Calcospherites In Rabbit Incisor Predentin, H. Mishima, Y. Kunuki, T. Sakae, Y. Kozawa, N. Watabe

Scanning Microscopy

Calcospherites from the lower incisor dentin of rabbits were investigated by scanning and transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and electron diffraction analyses. In the labial predentin, globular calcospherites of 8-31 μm were present at the root apex, decreasing in size toward the incisal region. The calcospherites at the intermediate region were of mulberry- as well as of spindle-shape of 1.5-4 μm diameter. The incisal pulp horn contained micro-calcospherites of 0.3-0.6 μmin diameter. In the lingual predentin, small granular calcospherites of 1. 8-3 μm were present at the root apex, increasing in size toward the intermediate region. Ultrathin …

Ultra-High Resolution Scanning Electron Microscopic Studies On The Sarcoplasmic Reticulum And Mitochondria In Various Muscles: A Review, Takuro Ogata, Yuichi Yamasaki

Scanning Microscopy

The three-dimensional structure of the sarcoplasmic reticulum (SR), transverse (T)-axial tubular system and mitochondria in various muscles was examined by means of ultra-high resolution scanning electron microscopy (SEM) after removal of the cytoplasmic matrices and myofilaments by the aldehyde-osmium-DMSO-osmium procedure. The striated muscles reviewed and presented are twitch and slow fibers of the frog, twitch and slow fibers of the chicken, twitch extrafusal fibers and intrafusal fibers of the rat, and cardiac muscle fibers of the rat and dog. In all of these striated muscle fibers, T-tubules run transversely and are coupled with terminal cisternae forming triads or dyads. Sarcotubules …

Strain Distribution During Growth Of Ge/Si(001) And The Effect Of Surfactant Layers, J. E. Macdonald, J. M. C. Thornton, A. A. Williams, P. Ashu, C. C. Matthai, H. A. Van Der Vegt, E. Vlieg

Scanning Microscopy

Grazing incidence X-ray diffraction has been employed to determine directly the distribution of strain in the plane of the interface during deposition of Ge onto Si(001). The corresponding strain distribution has also been deduced for a relaxed island whose atomic structure has been determined by molecular dynamics. The results illustrate the central role of elastic deformation of islands in the initial stage of strain relief. The results are also compared with those for growth with a Sb surfactant layer which suppresses island formation. An investigation of surfactant-like behaviour is also presented for homoepitaxial growth of Ag on Ag(111), where sub-monolayer …

Present Developments In Image Analysis, Peter Smart, Xiaoling Leng

Scanning Microscopy

The paper discusses novel methods of analysing oriented textures, explains some of the problems which had to be overcome to make these methods work, and indicates where future developments might be expected. This has required improvements in the methods of intensity gradient analysis, the development of large filter methods for mapping features defined in terms of their texture, and the introduction of ideas from the theory of regionalised variables.

Influence Of Annealing On The Interface Structure And Strain Relief In Si/Ge Heterostructures On (100) Si, D. J. Lockwood, J. -M. Baribeau, T. E. Jackman, P. Aebi, T. Tyliszczak, A. P. Hitchcock, R. L. Headrick

Scanning Microscopy

Research work on the general problem of the nature and thermal stability of the Si/Ge semiconductor interface is reviewed. We report on our recent studies of the interface structure in [(Si)_m(Ge)_n]_p superlattices and (Ge)_n layers buried in Si as revealed by Raman scattering, extended X-ray absorption fine structure, and X-ray techniques. Strain relaxation and interdiffusion in the superlattices caused by annealing have been investigated, and it is found that considerable strain-enhanced intermixing together with partial relaxation of Ge-Ge bonds occurs even for very short anneal times at 700°C. Further annealing leads to diffusion at …

Electron Beam Lithography For Large Area Patterning 3: Data Conversion And Electron Beam Deflection Control, Susumu Hoshinouchi, Hiroaki Tobuse, Hidenobu Murakami, Ryuichi Shimizu

Scanning Microscopy

Electron beam direct writing technologies, specifically for the large area patterning of electronic devices such as printed wiring boards, are studied in this paper. The vector scanning method with two kinds of beam deflection, main-deflection and sub-deflection, has been adopted for the fabrication of circuit patterns of various line widths. The sub-deflection of high frequency oscillation is superimposed on the main-deflection, which allows for controlling each line width with ease. A data conversion and a deflection control system with several strategies have been developed to reduce the conversion time and the volume of output data. It is revealed that circuit …

Electron Beam Lithography For Large Area Patterning 4: Exposure Of Resist On Internal Surface Of A Through-Hole, Susumu Hoshinouchi, Akio Yoshida, Hidenobu Murakami

Scanning Microscopy

Electron beam direct writing technologies, specifically for the large area patterning of electronic devices such as printed wiring boards, are studied in this paper. The exposure characteristics of the resist on the internal surface of a through-hole are examined. A thick film resist which is composed mainly of unsaturated acrylic resins is prepared on the internal surface of the hole by an electrodeposition process.

It is proven that a 20 μm thick resist on the internal surface can be exposed efficiently by a 60 keV electron beam. This phenomenon becomes even stronger by placing a gold plated metal plate on …

A Scanning Electron Microscopic Study Of The Chick Chorioallantoic Membrane: Cell Death And The Involvement Of Oxygen Free Radicals, A. Easterling, G. J. Burton, J. N. Skepper, M. H. Nasr-Esfahani

Scanning Microscopy

Cell death is a normal feature within the chick chorioallantoic membrane, occurring principally between days 10 and 14 of incubation.

Samples of chorioallantoic membrane were obtained on days 6, 8, 10, 12 and 14 of incubation, after the creation of artificial air chambers on day 3. These were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) after staining for acid phosphatase activity, and by light microscopy after demonstrating oxygen free radicals with nitro blue tetrazolium. On day 6, small defects in the plasmalemma, approximately 200 nm in diameter, could be seen by SEM. A sequence of events leading …

X-Ray Microanalysis Of Epithelial And Secretory Cells In Culture, Anne Von Euler, Eva Pålsgård, Christina Vult Von Steyern, Godfried M. Roomans

Scanning Microscopy

Cell cultures can be used to study ion transport processes. X-ray microanalysis of cell cultures at the cellular level gives interesting information that can complement electrophysiological and tracer studies. In this paper, methods for culturing and preparing a variety of epithelial and secretory cells (fibroblasts, insulinoma cells, bovine mammary epithelial cells, colon cancer cells) for X-ray microanalysis are presented. Results show that sometimes cell cultures are not homogeneous with respect to ion content or reaction to physiological stimuli. In colon cancer cell cultures, a "high K" and a "low K" cell subpopulation was found; these subpopulations also differed with respect …