bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of scanning electron microscopy in interpreting chenopodium remains from three archaeological sites in northwestern Iowa
Authors: Jones Douglas William 
Published: June 2020

Within the past 20 years, archaeobotanical research in the Eastern United States has documented an early agricultural complex before the dominance of the Mesoamerican domesticates (corn, beans, and squash) in late prehistoric and historic agricultural systems. This early agricultural complex consisted of domesticated plants such as Iva annua var.macrocarpa (Sumpweed or Marshelder), Hellanthus annuus (Sunflower) and Chenopodium berlandieri, (Goosefoot or Lasbsquarters), and heavily utilized plants such as Polygonum erectum (Erect Knotweed), Phalaris caroliniana (May grass), and Hordeum pusillum (Little Barley).Recent research involving the use of Scanning Electron Microscopy (SEM) specifically on Chenopodium has established diagnostic traits of wild and domesticated species seeds. This is important because carbonized or uncarbonized seeds are the most commonly recovered Chenopodium material from archaeological sites. The diagnostic seed traits assist archaeobotanists in identification of Chenopodium remains and provide a basis for evaluation of Chenopodium utilization in a culture's subsistence patterns. With the aid of SEM, an analysis of Chenopodium remains from three Late Prehistoric sites in Northwest Iowa (Blood Run [Oneota culture], Brewster [Mill Creek culture], and Chan-Ya-Ta [Mill Creek culture]) has been conducted to: 1) attempt seed identification to a species level, 2) evaluate the traits of the seeds for classification as either wild or domesticated, and 3) evaluate the role of Chenopodium utilization in both the Oneota and Mill Creek cultures.
Factors influencing adhesive bonding at the bone/implant interface
Authors: Martini Julie A. , Doremus Robert H. 
Published: June 2020

Tracy and Doremus have demonstrated chemical bonding between bone and hydroxylapatite with transmission electron microscopy. Now researchers ponder how to improve upon this bond in turn improving the life expectancy and biocompatibility of implantable orthopedic devices.This report focuses on a study of the- chemical influences on the interfacial integrity and strength. Pure hydroxylapatite (HAP), magnesium doped HAP, strontium doped HAP, bioglass and medical grade titanium cylinders were implanted into the tibial cortices of New Zealand white rabbits. After 12 weeks, the implants were retrieved for a scanning electron microscopy study coupled with energy dispersive spectroscopy.Following sacrifice and careful retrieval, the samples were dehydrated through a graduated series starting with 50% ethanol and continuing through 60, 70, 80, 90, 95, and 100% ethanol over a period of two days. The samples were embedded in LR White. Again a graduated series was used with solutions of 50, 75 and 100% LR White diluted in ethanol.
STM imaging of the sample or the tip ? an in situ REM study
Authors: Lo W.K. , Spence J.C.H. 
Published: June 2020

Image interpretation for Scanning Tunneling Microscopy (STM) is complicated by inadequate tip characterization. Tip and surface features can be difficult to separate, especially for rough surfaces. Figure 1, an STM image of a gold platelet deposited onto graphite, illustrates some of the possible problems. The doubled image of the platelet and step, for example, is a commonly encountered image artifact caused by tunneling from multiple tip asperities. The shape of the platelet(s) may also be an artifact since they are usually round. Ordinarily, to confirm the interpretation of such objects, experiments would be repeated using different tips and specimens to test for reproducibility. This is not an ideal procedure since the exact experimental conditions are difficult to duplicate. Alternatively, by comparing images of the same topography taken by STM and an independent imaging method, one can expose these artifacts.STM image artifacts were studied using an STM operating inside a Philips EM 400T TEM. This allowed imaging of the same region by Reflection Electron Microscopy (REM) and STM, independently of each other.
Quantification of grain boundary segregation in TiO2 by STEM
Authors: Ikeda Jeri Ann S. , Chiang Yet-Ming , Garratt-Reed Anthony J. 
Published: June 2020

A complete characterization of interfacial segregation involves knowing both the concentration of a solute or impurity and its spatial distribution, often at the subnanometer scale. In a number of materials problems, however, it is the segregation per unit area of interface that is of greatest interest. Problems involving charged interfaces are one example. In space-charge segregation at interfaces, the aliovalent solute density per unit area of interface is equivalent to the charge-density per unit area. Application of space-charge theory, in essence the application of Gauss' law and Poisson' equation allows the electrostatic potential to be deconvolved from segregation data.We have developed a new technique for measuring the solute segregation density at interfaces, here applied to the quantification of space-charge segregation at grain boundaries in TiO2. Using the results of a recent study by Furdanowicz et al. showing that beam broadening in nanoprobe STEM is much less than predicted by many conventional models, we use the VG HB5 in scan mode to analyze a volume containing the grain boundary.
EELS in the High-Resolution STEM
Authors: Brown L. M. 
Published: June 2020

The advent of efficient parallel recording systems for electron energy-loss spectra in electron microscopes, particularly those equipped with field emission guns which permit the formation of a useful nanometre probe, has transformed these instruments into remarkably versatile tools for solid state science. It is now possible in one's own laboratory to acquire spectra of quality comparable to those obtained from dedicated synchrotron sources, and in addition to record energy-filtered convergent-beam patterns and energy-selected images, in addition to the usual STEM outputs.The system in use in our laboratory has been developed by McMullan and co-workers. Its main feature is the use of a charge-coupled device to record both spectra and convergent beam patterns. The system is under constant development, and in its latest version offers a choice of three detectors: a slow scan CCD camera for PEELS and microdiffraction (CBED from the probe optimised for best spatial resolution); a TV-rate CCD for rapid readout, instrument alignment and ‘super-resolution’ experiments; and a specialised scintillator-photomultiplier bright-field detector.
Electron energy loss spectroscopy of diamond-like carbon thin films
Authors: Kulik J. , Lifshitz Y. , Lempert G.D. , Rotter S. , Rabalais J.W. , Marton D. 
Published: June 2020

Carbon thin films with diamond-like properties have generated significant interest in condensed matter science in recent years. Their extreme hardness combined with insulating electronic characteristics and high thermal conductivity make them attractive for a variety of uses including abrasion resistant coatings and applications in electronic devices. Understanding the growth and structure of such films is therefore of technological interest as well as a goal of basic physics and chemistry research. Recent investigations have demonstrated the usefulness of energetic ion beam deposition in the preparation of such films. We have begun an electron microscopy investigation into the microstructure and electron energy loss spectra of diamond like carbon thin films prepared by energetic ion beam deposition.The carbon films were deposited using the MEIRA ion beam facility at the Soreq Nuclear Research Center in Yavne, Israel. Mass selected C+ beams in the range 50 to 300 eV were directed onto Si {100} which had been etched with HF prior to deposition.
A conduction-cooled stage for high-resolution Cryo-SEM
Authors: Sheehan John G. 
Published: June 2020

The goal is to examine with high resolution cryo-SEM aqueous particulate suspensions used in coatings for printable paper. A metal-coating chamber for cryo-preparation of such suspensions was described previously. Here, a new conduction-cooling system for the stage and cold-trap in an SEM specimen chamber is described. Its advantages and disadvantages are compared to a convection-cooling system made by Hexland (model CT1000A) and its mechanical stability is demonstrated by examining a sample of styrene-butadiene latex.In recent high resolution cryo-SEM, some stages are cooled by conduction, others by convection. In the latter, heat is convected from the specimen stage by cold nitrogen gas from a liquid-nitrogen cooled evaporative heat exchanger. The advantage is the fast cooling: the Hexland CT1000A cools the stage from ambient temperature to 88 K in about 20 min. However it consumes huge amounts of liquid-nitrogen and nitrogen gas: about 1 ℓ/h of liquid-nitrogen and 400 gm/h of nitrogen gas. Its liquid-nitrogen vessel must be re-filled at least every 40 min.
In situTEM measurements of the electrical properties of interface dislocations
Authors: Ross F. M. , Hull R. , Bahnck D. , Bean J. C. , Peticolas L. J. , King C. A. 
Published: June 2020

We describe an investigation of the electrical properties of interfacial dislocations in strained layer heterostructures. We have been measuring both the structural and electrical characteristics of strained layer p-n junction diodes simultaneously in a transmission electron microscope, enabling us to correlate changes in the electrical characteristics of a device with the formation of dislocations.The presence of dislocations within an electronic device is known to degrade the device performance. This degradation is of increasing significance in the design and processing of novel strained layer devices which may require layer thicknesses above the critical thickness (hc), where it is energetically favourable for the layers to relax by the formation of misfit dislocations at the strained interfaces. In order to quantify how device performance is affected when relaxation occurs we have therefore been investigating the electrical properties of dislocations at the p-n junction in Si/GeSi diodes.
Ex situ and In situ TEM study of the relaxation of thin films by the modified frank-read mechanism
Authors: LeGoues F.K. 
Published: June 2020

In recent papers, we have described a novel mechanism for strain relaxation of thin films. Because of its strong resemblance to the well known Frank-Read sources of dislocations, it was called the “Modified-Frank-Read” (MFR) mechanism. This process was first observed during the growth of compositionally graded SiGe/Si(001) thin films, where it results in dislocations pile-ups being injected deep into an initially perfect substrate, leaving the topmost part of the film relaxed and nominally defect free. This last observation opens the door to a wide range of electronic applications since it makes it possible to grow electronic grade buffer layers of arbitrary composition and lattice parameter.The exact mechanism of the reproduction of dislocations was identified through tilting experiment and analysis of several compositionally graded SiGe/Si(001) structures. These also provided the important parameters controlling this mode of strain relaxation. We thus demonstrated that the MFR mechanism corresponds to the multiplication of “corner dislocations” (dislocations whose line forms a 90° angle) by simultaneous glide on two (111) planes.
Degradation of visible cathodoluminescence from porous silicon
Authors: Batstone J.L. , Tischler M.A. , Collins R.T. 
Published: June 2020

Porous Si has recently been shown to luminesce efficiently in the visible region of the spectrum. This discovery has lead to much excitement at the prospect of developing Si-based optoelectronic devices. However, the mechanism of this visible luminescence from an indirect-gap semiconductor is still the subject of much debate. In addition, the peak wavelength and efficiency of the luminescence is extremely sensitive to the preparation conditions and subsequent treatment of the sample. In this paper, Cathodoluminescence (CL) data are presented to show the degradation of luminescence when the samples are exposed to an electron beam.Porous silicon films were prepared by anodically etching p− Si(001) substrates in a solution of HF: H2O:C2H5OH at current densities of 1-20mA/cm2. Cathodoluminescence was excited by electron beam irradiation of the samples in a JEOL JSM6400 scanning electron microscope (SEM) equipped with an Oxford Instruments wavelength-dispersive CL system and liquid He cold stage. Monochromatic CL images were obtained in the wavelength range 600-800nm.
The morphology and microstructure of polycrystalline CdTe thin films for solar cell applications
Authors: Jones K.M. , Hasoon F.S. , Swartzlander A.B. , Al-Jassim M.M. , Chu T.L. , Chu S.S. 
Published: June 2020

Polycrystalline thin films of II-VI semiconductors on foreign polycrystalline (or amorphous) substrates have many applications in optoelectronic devices. In contrast to the extensive studies of the heteroepitaxial growth of compound semiconductors on single-crystal substrates, the nucleation and growth of thin films of II-VI compounds on foreign substrates have received little attention, and the properties of these films are often controlled empirically to optimize device performance. A better understanding of the nucleation, growth, and microstructure will facilitate a better control of the structural and electrical properties of polycrystalline semiconductor films, thereby improving the device characteristics. Cadmium telluride (CdTe) has long been recognized as a promising thin-film photovoltaic material. Under NREL's sponsorship, the University of South Florida has recently developed a record high efficiency (14.6% under global AM1.5 conditions) thin-film CdS/CdTe heterojunction solar cell for potential low-cost photovoltaic applications. The solar cell has the structure:glass (substrate)/SnO2:F/CdS/CdTe/HgTe (contact)The CdS films were grown from an aqueous solution, while the CdTe films were deposited by the closespaced sublimation method.
Interface morphology of thermal oxide grown on polycrystalline silicon by different processes
Authors: Yen H. , Kvam E. P. , Bashir R. , Venkatesan S. , Neudeck G. W. 
Published: June 2020

Polycrystalline silicon, when highly doped, is commonly used in microelectronics applications such as gates and interconnects. The packing density of integrated circuits can be enhanced by fabricating multilevel polycrystalline silicon films separated by insulating SiO2 layers. It has been found that device performance and electrical properties are strongly affected by the interface morphology between polycrystalline silicon and SiO2. As a thermal oxide layer is grown, the poly silicon is consumed, and there is a volume expansion of the oxide relative to the atomic silicon. Roughness at the poly silicon/thermal oxide interface can be severely deleterious due to stresses induced by the volume change during oxidation. Further, grain orientations and grain boundaries may alter oxidation kinetics, which will also affect roughness, and thus stress.Three groups of polycrystalline silicon films were deposited by LPCVD after growing thermal oxide on p-type wafers. The films were doped with phosphorus or arsenic by three different methods.
Formation of stacking-fault tetrahedra in low defect density oxygen-implanted silicon-on-insulator material
Authors: Lee June-Dong , Krause Stephen , Roitman Peter 
Published: June 2020

Fabrication of integrated circuits on SOI (Silicon-On-Insulator) material is very attractive because it offers high component density, immunity to latch-up and radiation hardness. Among various SOI techniques SIMOX Separation by IMplantation of OXygen) provides the best material, with carrier mobilities and defect densities approaching bulk silicon values, Early SIMOX wafers were implanted at temperatures below 600°C and annealed at high temperature (>1300°C), which gave a high defect density (109cm−2), including threading dislocations and narrow stacking faults (SFs), as shown in Figure 1. Higher temperature (>600°C) implantation of SIMOX reduced defect densities to 106cm-2 with pairs of narrow SFs in the top silicon layer, as shown in Figure 2. This paper describes a further reduction of defect density in SIMOX material through various annealing conditions, which has resulted in a defect density less than 105cm−2. A new formation mechanism for stacking fault tetrahedra is also discussed.Silicon (100) wafers were sequentially implanted (620°C) and annealed (at 1320°C for 5 hours) to doses of 0.5, 0.5, and 0.8×l018cm-2.
Characterization of stacked dielectric structures by TEM, electron holography and electron energy loss spectroscopy
Authors: Waytena G. , Weiss J.K. , Rez P. 
Published: June 2020

Thinner gate oxide regions, less than 100Å wide, are needed as MOS devices are scaled down in size to improve performance and increase the number of devices per chip. Triple layer dielectrics, in which a Si3N4 film is embedded between two SiO2 layers, are being investigated since the nitride layer provides a better diffusion barrier against dopants, metals and impurities as well as higher effective dielectric constant than a single layer of SiO2. To minimise atom diffusion, low temperature growth techniques such as Remote Plasma Enhanced Chemical Vapour Deposition (RPECVD) are being considered. As low temperature growth is not an equilibrium process non-stochiometric compositions can be formed. The aim of this work is to investigate structural characterisation of these layers in cross section by TEM and compositional analysis by PEELS.Two oxide-nitride-oxide (ONO) structures, both with nominally 50Å of nitride sandwiched between 10Åoxide layers in one specimen (10-50-10), and 30Å oxide layers in the second specimen (30-50-30) were grown by RPECVD at Research Triangle Institute. Cross section TEM specimens were prepared in according to standard procedures.
Antiphase boundaries and misfit dislocations in gaAs grown on ge(001)
Authors: Guelton N. , Saint-Jacques R.G. , Lalande G. , Cossement D. , Dodelet J.P. 
Published: June 2020

This work reports TEM investigation of the GaAs/Ge (100) heterojonction grown by close-spaced vapor transport (CSVT). It confirms that i) in layers deposited by this technique, the antiphase boundary (APB) density can be strongly reduced by using annealed misoriented substrates and that ii) the <011> misfit dislocations are mainly of the 60° type. It has been found that they are confined within 150 nm from the interface.The CSVT is an efficient and cost effective technique that allows the growth of epitaxial layers of semiconductors. A temperature gradient is maintained between the closely spaced (1mm) solid source and substrate. A transporting agent (water vapor) is used to react with the source and form volatile compounds which are subsequently decomposed at the surface of the substrate to form a thin film of the source material. Prior to initiation of deposition, the Ge substrate is heated at 825°C for 30 min in H2 atmosphere while the source temperature is maintained at 775°C, i.e. at a lower temperature to avoid any deposition on the substrate. This procedure allows elimination of oxydes and leads to step doubling.
Mapping the composition of materials at the atomic level
Authors: Ourmazd A. , Baumann F.H. , Kim Y. , Kisielowski C. , Schwander P. 
Published: June 2020

This paper briefly outlines how transmission electron microscopic lattice imaging techniques can be used to map the composition of crystalline materials at the atomic level.Under appropriate conditions, a conventional lattice image is a map of the sample structure, because the dominant reflections used to form lattice images are relatively insensitive to compositional changes in the sample. Such reflections may be termed “structural”. In many cystalline materials, compositional changes occur by atomic substitution on a particular subset of lattice sites. In these systems, compositional changes are accompanied by the appearance of reflections, which we name “chemical”. Such reflections, for example the (200) in the zinc-blende structure, owe their existence to chemical differences between the various atomic species present on the different lattice sites. For fundamental reasons these reflections are often weak; they come about because of incomplete cancellation of out of phase contributions from different sublattices. “Chemical lattice imaging” exploits dynamical scattering to maximize the intensity of such reflections, and uses the objective lens as a bandpass filter to enhance their contribution to the image.
A non-imaging concentrator for fiber optic mediated remote micro-Raman spectroscopy
Authors: McKinley B. J. , Sheem Sang , Lutz John , Milanovich Fred P. 
Published: June 2020

The recent availability of moderate power near-infrared diode lasers (780nm) and near-infrared sensitive ccd detectors have caused a noticeable resurgence in the application of Raman spectroscopy in analytical chemistry. We have long maintained an interest in Raman spectroscopy and have established a micro-Raman facility within the Chemistry Department of our organization. Recently, we have taken advantage of the aforementioned progress in spectroscopic equipment and have upgraded our micro-Raman facility to include a ccd detector and an imaging spectrograph.Since our micro-Raman spectrometer is designed around an ellipsoidal collection mirror, with Raman signal being directed through the illumination sample stage it has application to microscopic or small transparent samples. The improved performance of the device and the availability of highly transmissive optical fibers led one of us (B.J.M.) to propose an apparatus that could replace the existing illuminator with a miniature device that maintains a high collection efficiency and can be used remotely or in-situ by utilizing optical fibers.
Fluorescence imaging by confocal microspectrometry
Authors: Da Silva E. , Lenain B. , Manfait M. 
Published: June 2020

Confocal microfluorometry possesses many advantages. In particular, it provides the possibility to control the size of the analyzed surface and the depth of focus.The laser focussed on a line under microscope has been achieved either with cylindrical optics or by spot deflection (to conserve the Gaussian distribution of the laser beam).Associated with a 2D detector, this focussed line gives the spectral distribution for all the points of the line. A motorized stage in the direction perpendicular to the line gives all the data to rebuild a spectral image.We present a new scanning method rigorously confocal and giving, in addition, the possibility to change continuously the spread factor (defined by the number of pixels of the detector divided by the dimension of the line onto the sample under microscope), from few pixels by micrometer up to 20 pixels by micrometer.Figure 1 shows the principle of the system; a first optical scanner scans a line onto the sample under microscope.