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Seismic isolation of an electron microscope

Description: A unique two-stage dynamic-isolation problem is presented by the conflicting design requirements for the foundations of an electron microscope in a seismic region. Under normal operational conditions the microscope must be isolated from ambient ground noise; this creates a system extremely vulnerable to seismic ground motions. Under earthquake loading the internal equipment forces must be limited to prevent damage or collapse. An analysis of the proposed design solution is presented. This study… more
Date: January 1, 1980
Creator: Godden, W.G.; Aslam, M. & Scalise, D.T.
Partner: UNT Libraries Government Documents Department
open access

US Atom-Resolving Microscope Project

Description: The largest project in transmission electron microscopy in this country has recently been initiated. This project has been given the name Atomic Resolution Microscopy and its goal is to provide the instrumentation and expertise necessary to conduct materials research directly at the atomic level. Taking advantage of the best available technology in electron-optical design, its core instrumentation is a unique machine, the Atomic Resolution Microscope (ARM), which is to be built by commercial ma… more
Date: March 1, 1980
Creator: Gronsky, R.
Partner: UNT Libraries Government Documents Department
open access

AN EVALUATION OF POTENTIAL LINER MATERIALS FOR ELIMINATING FCCI IN IRRADIATED METALLIC NUCLEAR FUEL ELEMENTS

Description: Metallic nuclear fuels are being looked at as part of the Global Nuclear Energy Program for transmuting longlive transuranic actinide isotopes contained in spent nuclear fuel into shorter-lived fission products. In order to optimize the performance of these fuels, the concept of using liners to eliminate the fuel/cladding chemical interactions that can occur during irradiation of a fuel element has been investigated. The potential liner materials Zr and V have been tested using solid-solid diff… more
Date: September 1, 2007
Creator: Keiser, D. D. & Cole, J. I.
Partner: UNT Libraries Government Documents Department
open access

Experimental and theoretical studies of particle generation afterlaser ablation of copper with background gas at atmosphericpressure

Description: Laser ablation has proven to be an effective method for generating nanoparticles; particles are produced in the laser induced vapor plume during the cooling stage. To understand the in-situ condensation process, a series of time resolved light scattering images were recorded and analyzed. Significant changes in the condensation rate and the shape of the condensed aerosol plume were observed in two background gases, helium and argon. The primary particle shape and size distribution were measured… more
Date: May 31, 2007
Creator: Wen, Sy-Bor; Mao, Xianglei; Greif, Ralph & Russo, Richard E.
Partner: UNT Libraries Government Documents Department
open access

A CCD Camera with Electron Decelerator for Intermediate Voltage Electron Microscopy

Description: Electron microscopists are increasingly turning to Intermediate Voltage Electron Microscopes (IVEMs) operating at 300 - 400 kV for a wide range of studies. They are also increasingly taking advantage of slow-scan charge coupled device (CCD) cameras, which have become widely used on electron microscopes. Under some conditions CCDs provide an improvement in data quality over photographic film, as well as the many advantages of direct digital readout. However, CCD performance is seriously degraded… more
Date: March 17, 2008
Creator: Downing, Kenneth H; Downing, Kenneth H. & Mooney, Paul E.
Partner: UNT Libraries Government Documents Department
open access

STROBOSCOPIC IMAGE CAPTURE: REDUCING THE DOSE PER FRAME BY AFACTOR OF 30 DOES NOT PREVENT BEAM-INDUCED SPECIMEN MOVEMENT INPARAFFIN

Description: Beam-induced specimen movement may be the major factor that limits the quality of high-resolution images of organic specimens. One of the possible measures to improve the situation that was proposed by Henderson and Glaeser (Henderson and Glaeser, 1985), which we refer to here as 'stroboscopic image capture', is to divide the normal exposure into many successive frames, thus reducing the amount of electron exposure--and possibly the amount of beam-induced movement--per frame. The frames would t… more
Date: August 1, 2006
Creator: Typke, Dieter; Gilpin, Christopher J.; Downing, Kenneth H. & Glaeser, Robert M.
Partner: UNT Libraries Government Documents Department
open access

Emergence of Strong Exchange Interaction in the Actinide Series: The Driving Force for Magnetic Stabilization of Curium

Description: Using electron energy-loss spectroscopy in a transmission electron microscope, many-electron atomic spectral calculations and density functional theory, we examine the electronic and magnetic structure of Cm metal. We show that angular momentum coupling in the 5f states plays a decisive role in the formation of the magnetic moment. The 5f states of Cm in intermediate coupling are strongly shifted towards the LS coupling limit due to exchange interaction, unlike most actinide elements where the … more
Date: January 4, 2007
Creator: Moore, K; der Laan, G v; Haire, D; Wall, M; Schwartz, A & Soderlind, P
Partner: UNT Libraries Government Documents Department
open access

Markov Random Field Based Automatic Image Alignment for ElectronTomography

Description: Cryo electron tomography (cryo-ET) is the primary method for obtaining 3D reconstructions of intact bacteria, viruses, and complex molecular machines ([7],[2]). It first flash freezes a specimen in a thin layer of ice, and then rotates the ice sheet in a transmission electron microscope (TEM) recording images of different projections through the sample. The resulting images are aligned and then back projected to form the desired 3-D model. The typical resolution of biological electron microscop… more
Date: November 30, 2007
Creator: Moussavi, Farshid; Amat, Fernando; Comolli, Luis R.; Elidan, Gal; Downing, Kenneth H. & Horowitz, Mark
Partner: UNT Libraries Government Documents Department
open access

Determining the Critcial Size of EUV Mask Substrate Defects

Description: Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by sub… more
Date: February 28, 2008
Creator: Mccall, Monnikue M.; Han, Hakseung; Cho, Wonil; Goldberg, Kenneth; Gullikson, Eric; Jeon, Chan-Uk et al.
Partner: UNT Libraries Government Documents Department
open access

Applications of Lagrangian Dispersion Modeling to the Analysis of Changes in the Specific Absorption of Elemental Carbon

Description: We use a Lagrangian dispersion model driven by a mesoscale model with four-dimensional data assimilation to simulate the dispersion of elemental carbon (EC) over a region encompassing Mexico City and its surroundings, the study domain for the 2006 MAX-MEX experiment, which was a component of the MILAGRO campaign. The results are used to identify periods when biomass burning was likely to have had a significant impact on the concentrations of elemental carbon at two sites, T1 and T2, downwind of… more
Date: March 7, 2008
Creator: Doran, J. C.; Fast, Jerome D.; Barnard, James C.; Laskin, Alexander; Desyaterik, Yury; Gilles, Marry K. et al.
Partner: UNT Libraries Government Documents Department
open access

In-situ Studies of the Martensitic Transformation in Ti Thin Films using the Dynamic Transmission Microscope (DTEM)

Description: The {alpha} to {beta} transition in pure Ti occurs mainly by a 'martensitic type' phase transformation. In such transformations, growth rates and interface velocities tend to be very large, on the order of 10{sup 3} m/s, making it difficult to observe the transformation experimentally. With thin films, it becomes even more difficult to observe, since the large surface augments the nucleation and transformation rates to levels that require nanosecond temporal resolution for experimental observat… more
Date: November 21, 2005
Creator: LaGrange, T. B.; Campbell, G. H.; Colvin, J. D.; King, W. E.; Browning, N. D.; Armstrong, M. R. et al.
Partner: UNT Libraries Government Documents Department
open access

Electron transport through single carbon nanotubes

Description: We report on the transport of energetic electrons through single, well aligned multi-wall carbon nanotubes (CNT). Embedding of CNTs in a protective carbon fiber coating enables the application of focused ion beam based sample preparation techniques for the non-destructive isolation and alignment of individual tubes. Aligned tubes with lengths of 0.7 to 3 mu m allow transport of 300 keV electrons in a transmission electron microscope through their hollow cores at zero degree incident angles and … more
Date: August 1, 2007
Creator: Schenkel, Thomas; Chai, G.; Heinrich, H.; Chow, L. & Schenkel, T.
Partner: UNT Libraries Government Documents Department
open access

DESIGN OF A MICROFABRICATED, TWO-ELECTRODE PHASE-CONTRAST ELEMENTSUITABLE FOR ELECTRON MICROSCOPY

Description: A miniature electrostatic element has been designed to selectively apply a ninety-degree phase shift to the unscattered beam in the back focal plane of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. The design involves a cylindrically shaped, biased-voltage electrode, which is surrounded by a concentric grounded electrode. Electrostatic calculations have been used to determine that the fringing fields in the region of the scattered elect… more
Date: September 20, 2006
Creator: Cambie, Rossana; Downing, Kenneth H.; Typke, Dieter; Glaeser,Robert M. & Jin, Jian
Partner: UNT Libraries Government Documents Department
open access

Background X-ray Spectrum of Radioactive Samples

Description: An energy-dispersive X-ray spectrometer (EDS) is commonly used with a scanning electron microscope (SEM) to analyze the elemental compositions and microstructures of a variety of samples. For example, the microstructures of nuclear fuels are commonly investigated with this technique. However, the radioactivity of some materials introduces additional X-rays that contribute to the EDS background spectrum. These X-rays are generally not accounted for in spectral analysis software, and can cause mi… more
Date: February 1, 2008
Creator: Yee, Shannon & Janney, Dawn E.
Partner: UNT Libraries Government Documents Department
open access

Determining the critical size of EUV mask substrate defects

Description: Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by sub… more
Date: May 26, 2008
Creator: Goldberg, Kenneth A.; Gullikson, Eric M.; Han, Hakseung; Cho, Wonil; Jeon, Chan-Uk & Wurm, Stefan
Partner: UNT Libraries Government Documents Department
open access

Rampant changes in 5f 5/2 and 5f 7/2 filling across the light and middle actinide metals

Description: We examine the branching ratio of the N{sub 4,5} (4d {yields} 5f ) spectra of Th, U, Np, Pu, Am, and Cm metal using electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM), together with many-electron atomic spectral calculations and the spin-orbit sum rule. Our results show that: (1) The actinide metals Pu, Am, and Cm exhibit intermediate coupling. (2) The intermediate coupling values for the 5f states as calculated using a many-electron atomic model are correct fo… more
Date: April 3, 2007
Creator: Moore, K; der Lann, G v; Wall, M; Schwartz, A & Haire, R
Partner: UNT Libraries Government Documents Department
open access

Atomic Structure of Pyramidal Defects in GaN:Mg; Influence ofAnnealing

Description: The atomic structure of the characteristic defects (Mg-rich hexagonal pyramids) in p-doped bulk and MOCVD GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects, confirmed also with positron annihilation. The inside walls of the cavities were covered by GaN of reverse polarity compared to the matrix. Defects in bulk GaN:Mg were almos… more
Date: October 3, 2005
Creator: Liliental-Weber, Z.; Tomaszewicz, T.; Zakharov, D.; O'Keefe, M.; Hautakangas, S.; Saarinen, K. et al.
Partner: UNT Libraries Government Documents Department
open access

Electron sputtering in the analytical electron microscope: Calculations and experimental data

Description: The environment of the electron microscope is particularly severe when one considers the energy deposited in a specimen during typical experimental conditions. Conventional imaging experiments tend to employ electron current densities ranging from approx.0.1 to 1 A/cm/sup 2/ while during microanalysis conditions probe current densities can range from 10 to values as high as 10/sup 5/ A/cm/sup 2/. At 100 kV this corresponds to power densities from 100 Kilowatts/cm/sup 2/ to 10/sup 4/ Megawatts/c… more
Date: March 1, 1987
Creator: Zaluzec, N.J. & Mansfield, J.F.
Partner: UNT Libraries Government Documents Department
open access

Quantitative x-ray microanalysis in an AEM: instrumental considerations and applications to materials science

Description: There are a wide variety of instrumental problems which are present to some degree in all AEM instruments. The nature and magnitude of these artifacts can in some instances preclude the simple quantitative interpretation of the recorded x-ray emission spectrum using a thin-film electron excitation model; however, by judicious modifications to the instrument these complications can be effectively eliminated. The specific operating conditions of the microscope necessarily vary from one analysis t… more
Date: January 1, 1979
Creator: Zaluzec, N J
Partner: UNT Libraries Government Documents Department
open access

Background fitting for electron energy-loss spectra

Description: Microanalysis using electron energy loss spectroscopy is now well established. In order to assess true edge profiles and obtain integrated intensities of the inner shell ionization edges of interest, it is first necessary to subtract the background. Usually a simple inverse power law is used, but for some spectra this form does not fit well. An alternative form which results in superior fits is described.
Date: 1981~
Creator: Bentley, James; Lehman, G.L. & Sklad, P.S.
Partner: UNT Libraries Government Documents Department
open access

Calculated sputtering and atomic displacement cross-sections for applications to medium voltage analytical electron microscopy

Description: The development of medium voltage electron microscopes having high brightness electron sources and ultra-high vacuum environments has been anticipated by the microscopy community now for several years. The advantages of such a configuration have been discussed to great lengths, while the potential disadvantages have for the most part been neglected. The most detrimental of these relative to microcharacterization are the effects of electron sputtering and atomic displacement to the local specime… more
Date: August 1, 1987
Creator: Bradley, C.R. & Zaluzec, N.J.
Partner: UNT Libraries Government Documents Department
open access

Empirical technique to measure x-ray production and detection efficiencies in the analytical electron microscope

Description: In the present work, a technique is proposed to experimentally measure the effective x-ray production and detection efficiency in pure element standards. This technique supplements and in some cases is preferable to the multi-element standard technique. Measurements of effective x-ray production and detection efficiencies are expected to be preferable to the standardless technique in cases where pure element samples can be prepared since the most uncertain parameters in the standardless techniq… more
Date: January 1, 1985
Creator: King, W.E.
Partner: UNT Libraries Government Documents Department
open access

Performance of a field emission gun TEM/STEM

Description: First experimental results on a Phillips EM 400 TEM/STEM fitted with a field-emission electron gun and objective twin lens are given here. Operation of the FEG is reliable up to maximum design voltage (120 kV). Highest resolution achieved in TEM was 1.9 A fringe. A wide variety of diffraction modes were demonstrated, ranging from CBDP from a small area (approx. 10 A dia) in STEM mode to SAD with angular resolution of 8 ..mu..rad in TEM mode. The EDS sensitivity is very high. STEM imaging perfor… more
Date: January 1, 1979
Creator: Carpenter, R W & Bentley, J
Partner: UNT Libraries Government Documents Department
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