High-angular-resolution electron energy loss spectroscopy of hexagonal boron nitride

High-angular-resolution electron energy loss spectroscopy (EELS) is used to study the anisotropic behavior of the boron and nitrogen K ionization edges in h-BN. This work makes significant progress toward improving the anisotropy measurements. The authors show experimentally by EELS the vanishment of the p* peak existing in these K edges in agreement with electronic structure calculations and previous soft x-ray absorption spectroscopy measurements

Effects of ion implantation and temperature on radiation-induced segregation in Ni-9Al alloys

Effects of Ne and Sc implantation on radiation-induced segregation (RIS) in Ni-9at.%Al were studied in-situ using the high-voltage electron microscope/Tandem accelerator at ANL. A highly-focused 900- keV electron beam generated radial defect fluxes which, in turn, induced transport of Al atoms toward the center of the electron- irradiated area via the inverse Kirkendall effect. Radial segregation rate of Al atoms was monitored by measuring the diameter of the {gamma}{prime}-Ni{sub 3}Al zone which formed in the Al-enriched area during irradiation. Ne and Sc implantation effects on RIS were investigated at 550 C; Ne effects were also examined at 625 C to determine effect of temperature on ability of Ne to act as defect trapping sites, causing RIS suppression. It was found that the RIS suppression effect of Ne increased with irradiation temperature and that Sc had a small RIS suppression effect which increased with Sc implantation dose. Ne bubbles which formed during implantation are believed to be responsible for its strong suppression effect. 6 figs, 12 ref

Effects of Ion Implantation and Temperature on Radiation-Induced Segregation In Ni-9Al Alloys

Effects of Ne and Sc implantation on radiation-induced segregation (RIS) in Ni-9at.%Al were studied in-situ using the high-voltage electron microscope/Tandem accelerator at ANL. A highly-focused 900- keV electron beam generated radial defect fluxes which, in turn, induced transport of Al atoms toward the center of the electron- irradiated area via the inverse Kirkendall effect. Radial segregation rate of Al atoms was monitored by measuring the diameter of the {gamma}{prime}-Ni{sub 3}Al zone which formed in the Al-enriched area during irradiation. Ne and Sc implantation effects on RIS were investigated at 550 C; Ne effects were also examined at 625 C to determine effect of temperature on ability of Ne to act as defect trapping sites, causing RIS suppression. It was found that the RIS suppression effect of Ne increased with irradiation temperature and that Sc had a small RIS suppression effect which increased with Sc implantation dose. Ne bubbles which formed during implantation are believed to be responsible for its strong suppression effect. 6 figs, 12 ref

Structure factor measurement in TiAl and silicon

It proved impossible to obtain results with sufficient precision for TiAl reproducibly (<0.1%) from samples of different thicknesses. In order to ascertain the origin of this inconsistency, this study concentrates on the development of the experimental and theoretical tools required for such refinement and measurements for Si have been performed

Tele-Presence Microscopy: An interactive multi-user environment for Collaborative research using high speed networks and the Internet

Tele-Presence Microscopy (TPM) is an advanced concept in the integration of computers and high speed networks with scientific instruments for operation, control, communication, and research, which makes use of ANL`s Advanced Analytical Electron Microscope and Analytical Scanning Electron Microscope as development/test bed sites. Implementation of a TPM facility allows a user from a remote location to either observe and/or control state-of-the-art instrumentation in a real time interactive mode. Using TPM, a user will be able to {ital actively} participate in scientific investigations at unique resources such as user facilities without being physically present at those locations. Manufacturers would be able to configure demonstration equipment and to remotely service/diagnose the system. Students would be able to initiate tele- presence operation of instruments which may not be available at their host institution; they would also be able to consult an advisor or nonlocal expert on-line. The generic TPM/LabSpace system is composed of both software and hardware which operate in a client/server relationship

Gaussian optics calculations of the parameters of a magnetic sector energy analyzer

The design of a magnetic deflection system for use as an electron energy loss spectrometer can be a complex process if one takes the most general approach. However, for application to materials research the design process can be reduced to three basic steps. First, the qualitative features of the overall system are defined--i.e., incident electron energy, required resolution, type of magnet, the desired focal properties, etc. Secondly, the design parameters necessary to meet these requirements are calculated using the appropriate equations. Finally, once the magnetic field has been specified, ray-tracing techniques can be employed to verify the system response to the conditions defined in the first two steps. The calculation of the parameters of a uniform field magnetic sector analyzer capable of energy resolutions of 20 ppM or better are considered. Higher resolution is attainable; however, for most materials work, more important considerations are the attainment of double focusing to improve S/N, the minimization of aberrations and the achievement of a flat image plane to facilitate parallel data recording

Processing and quantification of x-ray energy dispersive spectra in the Analytical Electron Microscope

Spectral processing in x-ray energy dispersive spectroscopy deals with the extraction of characteristic signals from experimental data. In this text, the four basic procedures for this methodology are reviewed and their limitations outlined. Quantification, on the other hand, deals with the interpretation of the information obtained from spectral processing. Here the limitations are for the most part instrumental in nature. The prospects of higher voltage operation does not, in theory, present any new problems and may in fact prove to be more desirable assuming that electron damage effects do not preclude analysis. 28 refs., 6 figs

Two dimensional CCD (charged coupled device) arrays as parallel detectors in electron energy loss and x-ray wavelength dispersive spectroscopy

Parallel detection systems for spectroscopy have generally been based upon linear detector arrays. Replacing the linear arrays with two dimensional systems yields more complicated devices; however, there are corresponding benefits which can be realized for both x-ray and electron energy loss spectroscopy. The operational design of these systems, as well as preliminary results from the construction of such a device used for electron spectroscopy, are presented. 10 refs., 8 figs

Electron-energy-loss-spectra library

A wide range of specimens has been studied using EELS over the last few years, resulting in a fairly extensive data base being accumulated. This work is now being prepared for general distribution to the scientific community in the form of a spectral library and will be periodically updated as additional measurements are obtained. At present this study contains in excess of 100 edges and their corresponding low loss spectra for the elements: Li, Be, B, C, N, O, F, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Hf, Ta, W, Pt, Au, Pb, and Bi, recorded from nominally pure elements or stoichiometric compounds

Intermediate voltage AEM`s: Have they fulfilled their potentials?

This paper discusses the spectroscopic technologies XEDS and EELS. The performance and limitations are described