bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for a raised rim on pits in mica induced by keV/nucleon ions
Authors: Fei L. , Fraundorf P. 
Published: June 2020

Nuclear tracks have been extensively studied and widely used in applications like archeological and geological dating, solar flare iostope determination, extraterrestrial material studies, super heavy elementary particle searches, etc. for more than three decades. Recently, scanning force microscopy (SFM) has proven to be useful for studying the pits induced by ions in the track recording energy range from several keV to several MeV per nucleaon on track recording material (e.g. mica) surfaces. SFM can provide topographical information on chemically etched orunetchedtrack pits at near atomic resolution in all three dimensions.We report here using a commercial SFM (NanoScope III, Digital Instruments, CA) in the study of a muscovite mica surfaces irradiated with 150keV Ar+ions. The mica was freshly cleaved before the irradiation. The SFM was operated with the amplitude resonance (tapping) mode to lower the interaction between a tip and specimen. We found pits on the mica surface after, but not before the irradiation, like those shown in Fig. la. Their number density was orders of magnitude less than the expected argon flux.
In or on? Location of noble metal particles on zeolite/binder support
Authors: Spinnler G. E. , Liu J. 
Published: June 2020

The location of metal particles contained in a zeolite-alumina binder support matrix has been difficult to solve using analytical techniques including electron microscopy. Imaging of metal particles, particularly noble metal particles on relatively light matrices such as zeolites or aluminas, has been easily accomplished using high angle annular darkfield imaging (HAADF). Since transmission imaging provides a projection through the sample, location of the particles in the sample or on the surface is not obvious. Surfacesensitive signals such as secondary electrons (SE) and Auger electrons (AE) are necessary to detect particles on the sample surface. HAADF, SE, and AE imaging have been applied to locate noble metal particles in a zeolite support with an alpha alumina binder.The samples were analyzed in a UHV HB501S STEM (MIDAS, Microscope for Imaging and Diffraction Analysis of Surfaces) at the Center for High Resolution Electron Microscopy at Arizona State University. The samples were prepared by crushing and dry deposition on a holey carbon grid.
Defect formation in oxygen-multiply implanted silicon-on-insulator material
Authors: Park J.C. , Lee J.D. , Krause S.J. 
Published: June 2020

High dose oxygen implantation (SIMOX) has been a successful fabrication technology of silicon-on-insulator (SOI) material for CMOS circuits with reduced power consumption and higher operating speed. However, high density (~108 cm-2) of the through-thickness defects (TTD) in the top Si layer of SIMOX is one of the most serious problems. Hill et al. reported multiple implant/anneal method to remarkably reduce defect densities to <104 cm-2. In the multiple implant/anneal material, however, ~106 cm2 of the final dominant defects, including stacking fault pyramids (SFP) and the precipitate-dislocation complexes (PDC), still remained after high temperature annealing. In this work, the microstructures and formation mechanism of the final defects were studied by various TEM techniques.Silicon (100) wafers were sequentially triple implanted to doses of 6/6/6×l017 at 200kev and 620°C. After each implantation the wafers were held at 1000°C for 2 hours and annealed at 1325°C for 4 hours in argon ambient plus 5% oxygen. Cross-section (XTEM) and plan-view (PTEM) transmission electron microscopy specimens were examined by using a weak beam dark field (WBDF) and high resolution electron microscopy (HREM) techniques in JEM 2000FX and Topcon 002B operating at 200kev.
TEM and AFM studies of structural defects in α-GaN films
Authors: Qian W. , Skowronski M. , De Graef M. , Rohrer G. , Doverspike K. , Rowland L. B. , Gaskill D. K. 
Published: June 2020

Interest in wide band-gap GaN and related group-III nitrides has grown recently due to their potential applications for short wavelength optoelectronic devices. One of the main obstacles for their application is the high density of defects formed during heteroepitaxy. Though important progress has been made by using a low temperature A1N buffer layer% recently reported films still contain a defect density (mainly threading dislocations) on the order of 1010 cm-2. This paper reports our current studies of structural defects in α-GaN thin films grown on a-plane (110) and c-plane (0001) sapphire substrates by organometallic vapor phase epitaxy (OMVPE). Atomic force microscopy (AFM), conventional and high resolution transmission electron microscopy (TEM) were used to investigate the nature and origin of these defects.Single crystal α-GaN films were grown using a low temperature A1N or GaN buffer layer in an inductively-heated, water cooled, vertical OMVPE reactor operated at 57 torr.
High energy As ion implantation to GaAs
Authors: Jasinski J. , Liliental-Weber Z. , Kaminska M. , Washburn J. , Jagadish C. 
Published: June 2020

Over the last few years there have been many studies of GaAs layers grown in the temperature range from 180°C to 300°C called LT-GaAs. These studies were motivated by the potential applications of that material in microwave and fast optoelectronic devices. Annealed LT-GaAs layers have interesting electrical properties including high resistivity and short photocarrier lifetime connected with the nonstoichiometry of that material. However, it is still not clear whether arsenic antisite point defects or arsenic precipitates formed during annealing cause these interesting properties of LT GaAs.A second method of creating highly nonstoichiometric GaAs beside low temperature MBE growth is implantation with a high dose of arsenic. This method first applied two years ago showed that 200 keV arsenic ion implantation also leads to semi-insulating properties and that successive post-implantation annealing results in arsenic precipitate formation, similar to that observed in LT GaAs. Recently, more elaborate studies concerning photocarrier lifetime, resistivity, mobility and some structural characteristics were performed on GaAs implanted with high energy arsenic ions.
Microstructure and microanalysis of neodymium iron boron magnets sintered with aluminum
Authors: Chandramouli M. , Thomas G. 
Published: June 2020

The magnetic properties of NdFeB magnets sintered with 15 vol.% Al at 850 °C and 1000 °C for 1 hour are dependent on microstructure. Complementary use of SEM and TEM techniques are crucial to elucidate the microstructural differences responsible for the properties. The hysterisis loops shown in Fig. 1 indicate that the higher sintering temperature sample has a larger dip near zero applied field and lower coercivity. This behavior is consistent with a larger volume fraction of soft magnetic phases.Microstructural analysis performed using a JEOL 35 CF SEM does not show significant differences between the samples. As revealed in Fig. 2, a representative backscattered image of the 850 °C sample, the microstructure consists of dark pockets with a gray matrix region with small, bright contrast pockets. Quantitative microanalysis confirmed that the gray matrix phase had a composition consistent with Nd2Fe14B, the ferromagnetic phase in conventionally prepared Nd-Fe-B permanent magnets. The small bright pockets were found to have a high Nd content while the large dark pockets were rich in Al.
Determination of the degree of radial order in Kevlar fibers using x-ray linear dichroism microscopy
Authors: Smith A. P. , Ade H. , Hsiao B. , Subramoney S. 
Published: June 2020

The Scanning Transmission X-ray Microscope (STXM) located at beamline X1A at the National Synchrotron Light Source at Brookhaven National Laboratory can be used to acquires high resolution, chemically and orientationally sensitive images with 50 nm spatial resolution, as well as point spectra from 0.1 μm2 areas. Chemical (valence) sensitivity can be achieved via the X-ray Absorption Near Edge Structure (XANES) at the carbon K edge. In addition, linear dichroism microscopy exploits the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays. Previous x-ray linear dichroism microscopy work has demonstrated the ability to determine the orientation of specific chemical groups within polymeric systems at high spatial resolution. Here, we have extended this technique to quantitatively determine the degree of radial order in various grades of poly(p-phenylene terephthalamide) (Kevlar™) fibers.The orientational dependence of the absorption cross-section yields “butterfly” patterns when thin sections of certain grades of Kevlar fibers cut at 45° with respect to the fiber axis are imaged at specific photon energies.
Characterization of pulsed laser deposited Zno-WS2 thin solid film lubricants
Authors: Walck S. D. , Zabinski J. S. , McDevitt N.T. , Bultman J. E. 
Published: June 2020

ZnO-WS2 is a potential high temperature solid film lubricant for aerospace applications that exhibits adaptive lubricant behavior. An adaptive lubricant undergoes phase and/or chemical changes in response to thermal, environmental, and tribological conditions; with the resulting phase or wear debris also being lubricious. Pulsed laser deposited (PLD) ZnO-WS2 thin films deposited at room temperature (RT) and wear-tested at room temperature have been shown to have coefficients of friction of 0.04 or less which are comparable to WS2 films, but have much longer wear lives. In the as-deposited state, PLD ZnO-WS2 films are amorphous, but when wear-tested, the phases WS2, WO3, and ZnWO4 are produced. Of these, WS2 is a lubricant phase at low temperatures (⪯ ~450°C) while ZnWO4 is a lubricant phase above about 600°C. The purpose of this work was to characterize the microstructural and chemical changes that occur when the RT-PLD ZnO-WS2 films are heated in air.The RT-PLD ZnO-WS2 films were deposited in a system having a base pressure of 9×l0-7 Pa with a typical pressure during deposition of 6×10-5 Pa.
Surface chemical sensitivity combined with high-resolution EM
Authors: Landree E. , Collazo-Davila C. , Grozea D. , Plass R. , Jayaram G. , Marks L.D. , Stair P.C. 
Published: June 2020

Although high resolution electron microscopy (HREM) has proved to be an invaluable tool in the study of surfaces, one critical drawback is its inability to obtain specific surface chemical state information. The ideal investigation would combine the imaging capabilities of HREM with the surface chemical information obtainable from X-ray Photon Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) without exposing the sample surface to possible contaminants. We have taken a step in this regard with the addition of a new Specimen Preparation Evaluation and Analysis for Research (SPEAR) side chamber to the existing Hitachi UHV-9000 microscope, designed by Superior Vacuum Technology (Figure 1). Currently we are able to combine all of the imaging tools of HREM with surface chemical sensitivity, in an attempt to achieve the ideal surface analysis instrument.Samples are introduced and retrieved from the system through a load-lock mechanism. Pumped by a 210 Liter/sec Balzers’ Turbomolecular pump, this introduction chamber is capable of going from atmospheric pressure to 10-10 torr in four to eight hours.
The CM120 Biotwin: a high-contrast objective lens, optimum cryo-vacuum and improved EDX performance
Authors: Lücken Uwe , Felsmann Michael , Busing Wim M. , de Jong Frank 
Published: June 2020

A new microscope for the study of life science specimen has been developed. Special attention has been given to the problems of unstained samples, cryo-specimens and x-ray analysis at low concentrations.A new objective lens with a Cs of 6.2 mm and a focal length of 5.9 mm for high-contrast imaging has been developed. The contrast of a TWIN lens (f = 2.8 mm, Cs = 2 mm) and the BioTWTN are compared at the level of mean and SD of slow scan CCD images. Figure 1a shows 500 +/- 150 and Fig. 1b only 500 +/- 40 counts/pixel. The contrast-forming mechanism for amplitude contrast is dependent on the wavelength, the objective aperture and the focal length. For similar image conditions (same voltage, same objective aperture) the BioTWIN shows more than double the contrast of the TWIN lens. For phasecontrast specimens (like thin frozen-hydrated films) the contrast at Scherzer focus is approximately proportional to the √ Cs.
The information limit of a 200kv field emission TEM
Authors: Kaneyama T. , Kawasaki M. , Tomita T. , Honda T. , Kersker M. 
Published: June 2020

The Point resolution of a transmission electron microscope is normally defined by the reciprocal of the spatial frequency of the first zero in the phase contrast transfer function at the Scherzer defocus condition. When a field emission gun (FEG) is used as the electron source, the information limit, that point at which the contrast beyond the first zero goes to zero contrast, becomes equally important. We have investigated the primary microscope parameters that affect the information limit.A 200kV FE-TEM (JEM-2010F) equipped with a ZrO/W shottkey emitter and Gatan Parallel EELS (PEELS) was used for the experiments. The aberration coefficients of the objective lens are Cs = 1mm and Cc = 1.4mm. The specimen used is an evaporated amorphous Ge thin film with small gold islands.The resolution performance of the microscope depends not only on the performance of the objective lens, the high voltage stability, stability of the lens and deflector power supplies, operating parameters of the FEG, and the overall mechanical stability of the microscopes.
Estimation and analysis of 3-D chromosome motion
Authors: Marshall W.F. , Agard D.A. , Sedat J.W. 
Published: June 2020

The mechanical properties of chromosomes in vivo are at present poorly characterized, yet an understanding of such properties is likely to be important for understanding both the behavior of chromosomes during mitosis as well as the establishment and maintenance of specific chromosome configurations in the nucleus. In order to better investigate the mechanics of chromosomes inside living cells we have developed algorithms for quantitative analysis of chromosome motion. This allows us to directly determine chromosome mobility, and to visualize the trajectories of specific regions, such as telomeres or centromeres. Previously developed tools for analysis of 3D structure can then be extended to 4 dimensions, allowing quantitative description of chromosome behavior. The motion vector field itself can also be analyzed for specific patterns of motion.Three dimensional motion estimation is difficult in fluorescence microscopic images, due to limited spatial resolution, particularly in the axial direction, which result in a significant aperture problem because each part of a chromosome looks identical to any other part of any other chromosome, such that intensity patterns are not useful in motion estimation.
Analytical solutions for complex problems using multiple diagnostic techniques
Authors: Heimbrook L. A. 
Published: June 2020

The ability to apply multiple diagnostic techniques to complex material, biological, and device problems with the goal of obtaining analytical solutions is the daily objective of the typical analytical laboratory. This paper will describe the use of both microscopy and surface analysis diagnostic tools to evaluate routine and highly complex material and device problems often found in the semiconductor industry. The characterization requirements for silicon and III-V materials and devices cover a wide range of technology research and development programs. These programs involve the characterization of starting materials, doping and implant technologies, thin film technology, particle and contamination issues and final device inspection. Continued advances in ultra-shallow silicon devices and multi-quantum-well (MQW) lasers rely on the accurate introduction of doping elements, the ability to deposit high quality materials of specified layer thicknesses and on advances in fabrication and characterization tools.The complex analysis problems of evaluating ultra shallow junctions in sub-micron silicon devices and the measurement of grating depths and duty cycles in semiconductor lasers are the characterization challenges which will be addressed in this paper.
Three muscle isoforms of α-actinin form unipolar actin bundles
Authors: Taylor K. A. , Taylor D. W. 
Published: June 2020

α-Actinin is an F-actin binding protein that is ubiquitous in eucaryotic cells. It is the smallest member of the spectrin superfamily and consists of two, identical polypeptide chains of 95-103 kDa. α-Actinin is an elongated molecule of 34 nm length and consists of a string of peptide domains with different functions. The N-terminal domain of ˜255 residues has actin binding activity, the central core consists of four 122 residues triple-helical repeats and the C-terminal domain contains two E-F hand Ca2+ binding motifs.The physiological importance α-actinin lies in its subcellular location and its interactions with other proteins. The F-actin crosslinking activity of α-actinin is its best known function. In striated muscle aactinin is found in the Z-disk. In smooth muscle, α-actinin is found in both cytoplasmic dense bodies, which are analogs of the Z-disk, and adhesion plaques, which are cell membrane anchoring sites of actin filaments. In dense bodies and Z-disks, oppositely oriented, unipolar bundles of actin filaments overlap so it has been commonly assumed that α-actinin is functioning as a bipolar crosslinker but the unipolar orientation of actin filaments at the cell membrane implies a unipolar bundling activity.
Cryo-electron and optical microscopy study of lipid-encapsulated microtubules
Authors: Bisher M. E. , Fygensont D. K. , Booy F. , Libchabert A. , Treacy M. M. J. 
Published: June 2020

The dimeric protein tubulin is found in every eukaryotic cell. In the presence of GTP and Mg++ cations, tubulin polymerizes into long hollow cylinders known as microtubules, that are 24 nm in diameter and can grow as long as 10-100 μm in length. Microtubules play an important role in living cells: they act as guides for internal molecular transport (most notably the separation of genetic material during anaphase in cell division), they are a major component of the cytoskeleton, and are important structural constituents of cilia and flagellae. Locomotion, morphogenesis and reproduction, are fundamental cellular processes that rely on the polymerization of microtubules and on their ability to re-organize - a feature termed dynamic instability.Tubulin, purified from fresh cow brain, exhibits this dynamic instability in the laboratory in the absence of microtubule-associated protein. Length fluctuations can be observed by differential interference contrast (DIC) optical microscopy. The instability persists when tubulin is encapsulated in lipid vesicles (liposomes), formed by adding the phospholipids DOPC and DOPS, and applying the freeze-thaw technique to the mixture. Fig. 1 shows a DIC optical micrograph of a ˜5 (im lipid vesicle that is distorted, or impaled, by a 12 μm rod which is presumably a microtubule, or a bundle of microtubules. Frequently, such microtubules are observed to buckle because of reaction forces from the membrane.
New tools for Atomic Force Microscopy
Authors: Prater C. B. 
Published: June 2020

The Atomic Force Microscope (AFM) has been widely used in the physics, chemistry, and materials science communities, and is becoming more common in life sciences research. To better serve the biological community, new instruments have been developed recently that combine AFM and various forms of optical microscopy including EPI-fluorescence, DIC, and confocal microscopy. In addition, new techniques like fluid Tapping Mode™ have been developed to allow gentle, non-destructive imaging of biological samples, including live specimens in physiological conditions. Other new techniques can provide information about sample elasticity or molecular adhesion along with nanometerscale topography measurements.Until recently, most AFMs scanned the sample under a stationary probe using a small piezoelectric scanner. This arrangement placed serious limits on the size and type of sample that could be used as a sample substrate. Now instruments have been developed that scan the AFM probe over a fixed sample that then allows imaging of larger, more convenient sample substrates, including cover slips, slides, and even petri dishes.
Mussel adhesive protein as a novel substrate for Atomic Force Microscopy
Authors: D'Costa Neill P. , Hoh Jan H. 
Published: June 2020

Atomic Force Microscopy (AFM) requires immobilization of samples to a suitable substrate. Immobilized samples must withstand forces, particularly lateral forces, exerted by the tip during imaging. Air-drying is the simplest way of immobilizing molecules onto a substrate. However, this often compromises the integrity of structural features because of forces at the air-liquid interface. In solution the most common method is simple adsorption. While very convenient, this method works only for a limited number of samples. To overcome this problem procedures involving covalent chemical cross-linking have been developed. We have developed an alternative AFM substrate based on the mussel adhesive protein (MAP) from Mytilus edulis. This substrate is simple to prepare and can immobilize a wide range of samples, including gold particles, silica spheres, proteins, and nucleic acids.MAP is a polyphenols marine adhesive by which the mussel attaches itself to different surfaces. Studies of purified MAP indicate that it possesses a unique chemistry.
Critical issues in the application of image cytometry to the early detection of lung and cervical cancer
Authors: Garner D.M , MacAulay C.E. , Palcic B. 
Published: June 2020

Screening for cervical cancer (“Pap screening”) is probably the largest single application of absorbance microscopy in medicine, with 50-60 million samples screened per year in the United States alone. Pap screening also represents one of the great success stories in cancer management having reduced the morbidity and mortality due to cancer of the uterine cervix by 50 - 80% in regions where mass Pap screening is carried out. Despite this success, the subjective manual examination of stained cellular specimens with a microscope in current Pap screening practice results in significant over treatment. We estimate that for every 30 women currently treated for early cervical cancer, only one would actually develop invasive cancer in the absence of the Pap screening programme.One key question then is: “Could image cytometry, the objective measurement of cells, improve the current Pap screening programmes by reducing the number of unnecessary medical interventions, without subjecting the patients to undo risk?”