Spatially resolved materials characterization with TEM

Research and development in material science require the understanding of structure and property relationship. In many instances, such a relationship at a local microstructural scale is crucial for a mechanistic insight. Spatially-resolved microtexture analyses based on both scanning and transmission electron microscopy have now become powerful tools for these studies. By these techniques, not only can a linkage be established between morphological and crystallographic components of the microstructure, grain boundary details can be obtained as well. The choice of the SEM- or TEM-based microtexture technique for a study, however, depends on the specific needs. Several industrial examples of applied and basic work will be used for illustration.Industrial deformation processes such as extrusion, rolling and forging are generally inhomogeneous. As a result, strain gradients, and consequently, microstructure gradients, are intrinsic to most industrial products. For example, a laboratory-produced plane strain extrusion of an Al-Zn-Mg-Cu alloy exhibits a range of complex grain structures (Fig. 1a).

Micro X-ray Fluorescence for Spatially Resolved Elemental Materials Characterization

10.2172/1054669 ◽

2012 ◽

Author(s):

George J Havrilla

Keyword(s):

Materials Characterization ◽

X Ray ◽

Spatially Resolved

Electron Channeling Patterns

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077700 ◽

1977 ◽

Vol 35 ◽

pp. 12-13

Author(s):

David C. Joy

Keyword(s):

Electron Diffraction ◽

Incidence Angle ◽

Photographic Plate ◽

Diffraction Effect ◽

Angle Of Incidence ◽

Bulk Single Crystal ◽

Time Resolved ◽

Electron Channeling ◽

Spatially Resolved ◽

Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

FT-IR microspectroscopic analysis of diseased white matter brain tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141214 ◽

1995 ◽

Vol 53 ◽

pp. 968-969

Author(s):

Steven M. Le Vine ◽

David L. Wetzel

Keyword(s):

White Matter ◽

Gray Matter ◽

Twitcher Mouse ◽

Grid Pattern ◽

Marked Contrast ◽

Spatially Resolved ◽

Ft Ir ◽

Ir Microspectroscopy ◽

Chemical Evidence

In situ FT-IR microspectroscopy has allowed spatially resolved interrogation of different parts of brain tissue. In previous work the spectrrscopic features of normal barin tissue were characterized. The white matter, gray matter and basal ganglia were mapped from appropriate peak area measurements from spectra obtained in a grid pattern. Bands prevalent in white matter were mostly associated with the lipid. These included 2927 and 1469 cm-1 due to CH2 as well as carbonyl at 1740 cm-1. Also 1235 and 1085 cm-1 due to phospholipid and galactocerebroside, respectively (Figs 1and2). Localized chemical changes in the white matter as a result of white matter diseases have been studied. This involved the documentation of localized chemical evidence of demyelination in shiverer mice in which the spectra of white matter lacked the marked contrast between it and gray matter exhibited in the white matter of normal mice (Fig. 3).The twitcher mouse, a model of Krabbe’s desease, was also studied. The purpose in this case was to look for a localized build-up of psychosine in the white matter caused by deficiencies in the enzyme responsible for its breakdown under normal conditions.

Ultra-spatially resolved synchrotron powered FT-IR microspectroscopy of individual cells of biological material

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140798 ◽

1995 ◽

Vol 53 ◽

pp. 884-885

Author(s):

David L. Wetzel ◽

John A. Reffner ◽

Gwyn P. Williams

Keyword(s):

Thermal Noise ◽

Spot Size ◽

Acquisition Time ◽

Thermal Source ◽

Signal To Noise ◽

Spatially Resolved ◽

Good Spatial Resolution ◽

Small Spot ◽

Ft Ir ◽

Ir Microspectroscopy

Synchrotron radiation is 100 to 1000 times brighter than a thermal source such as a globar. It is not accompanied with thermal noise and it is highly directional and nondivergent. For these reasons, it is well suited for ultra-spatially resolved FT-IR microspectroscopy. In efforts to attain good spatial resolution in FT-IR microspectroscopy with a thermal source, a considerable fraction of the infrared beam focused onto the specimen is lost when projected remote apertures are used to achieve a small spot size. This is the case because of divergence in the beam from that source. Also the brightness is limited and it is necessary to compromise on the signal-to-noise or to expect a long acquisition time from coadding many scans. A synchrotron powered FT-IR Microspectrometer does not suffer from this effect. Since most of the unaperatured beam’s energy makes it through even a 12 × 12 μm aperture, that is a starting place for aperture dimension reduction.

Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013554x ◽

1990 ◽

Vol 48 (2) ◽

pp. 388-389

Author(s):

A. M. Bradshaw

Keyword(s):

Photoelectron Spectroscopy ◽

Chemical Reactivity ◽

Target Material ◽

Orbital Energy ◽

Light Sources ◽

Analytical Technique ◽

Hartree Fock ◽

Spatially Resolved ◽

Koopmans Theorem ◽

Surface Analytical Technique

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

Layered and ion implantation specimens as possible reference materials for the electron-probe microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132893 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1652-1653

Author(s):

G. Remond ◽

R.H. Packwood ◽

C. Gilles ◽

S. Chryssoulis

Keyword(s):

Ion Implantation ◽

Reference Materials ◽

Analytical Techniques ◽

Thin Film Deposition ◽

Film Deposition ◽

X Ray ◽

Spatially Resolved ◽

Analytical Expressions ◽

Original Approach ◽

Depth Concentration

Merits and limitations of layered and ion implanted specimens as possible reference materials to calibrate spatially resolved analytical techniques are discussed and illustrated for the case of gold analysis in minerals by means of x-ray spectrometry with the EPMA. To overcome the random heterogeneities of minerals, thin film deposition and ion implantation may offer an original approach to the manufacture of controlled concentration/ distribution reference materials for quantification of trace elements with the same matrix as the unknown.In order to evaluate the accuracy of data obtained by EPMA we have compared measured and calculated x-ray intensities for homogeneous and heterogeneous specimens. Au Lα and Au Mα x-ray intensities were recorded at various electron beam energies, and hence at various sampling depths, for gold coated and gold implanted specimens. X-ray intensity calculations are based on the use of analytical expressions for both the depth ionization Φ (ρz) and the depth concentration C (ρz) distributions respectively.

EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164179 ◽

1996 ◽

Vol 54 ◽

pp. 342-343

Author(s):

S.J. Splinter ◽

J. Bruley ◽

P.E. Batson ◽

D.A. Smith ◽

R. Rosenberg

Keyword(s):

Electronic Structure ◽

Grain Boundaries ◽

Boundary Segregation ◽

Thin Layers ◽

Nominal Composition ◽

Spatially Resolved ◽

Service Lifetime ◽

Heat Treated ◽

Probe Size ◽

Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

Prospects for scanned-probe microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100167767 ◽

1994 ◽

Vol 52 ◽

pp. 6-7

Author(s):

Jean-Paul Revel

Keyword(s):

High Vacuum ◽

Physiological Saline ◽

Scanning Probe ◽

Aqueous Environment ◽

Whole Cells ◽

Material Scientist ◽

Biological Objects ◽

Spatially Resolved ◽

Atomic Force ◽

Scanned Probe Microscopy

In the last 50+ years the electron microscope and allied instruments have led the way as means to acquire spatially resolved information about very small objects. For the material scientist and the biologist both, imaging using the information derived from the interaction of electrons with the objects of their concern, has had limitations. Material scientists have been handicapped by the fact that their samples are often too thick for penetration without using million volt instruments. Biologists have been handicapped both by the problem of contrast since most biological objects are composed of elements of low Z, and also by the requirement that sample be placed in high vacuum. Cells consist of 90% water, so elaborate precautions have to be taken to remove the water without losing the structure altogether. We are now poised to make another leap forwards because of the development of scanned probe microscopies, particularly the Atomic Force Microscope (AFM). The scanning probe instruments permit resolutions that electron microscopists still work very hard to achieve, if they have reached it yet. Probably the most interesting feature of the AFM technology, for the biologist in any case, is that it has opened the dream of high resolution in an aqueous environment. There are few restrictions on where the instrument can be used. AFMs can be made to work in high vacuum, allowing the material scientist to avoid contamination. The biologist can be made happy as well. The tips used for detection are made of silicon nitride,(Si3N4), and are essentially unaffected by exposure to physiological saline (about which more below). So here is an instrument which can look at living whole cells and at atoms as well.