Corrections for surface films in microanalysis by EDS and EELS

1992 ◽  
Vol 50 (2) ◽  
pp. 1230-1231
Author(s):  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Hydrocarbon Contamination ◽  
Specimen Preparation ◽  
Surface Films ◽  
Ion Milling ◽  
Preferential Sputtering ◽  
Electron Energy Loss Spectrometry ◽  
Composition Determination ◽  
Analytical Electron ◽  
First Order Correction ◽  
Electron Energy Loss

Common artifacts on analytical electron microscope (AEM) specimens prepared from bulk materials are surface films with altered structure and composition that result from electropolishing, oxidation, hydrocarbon contamination, or ion milling (preferential sputtering or deposition of sputtered specimen or support material). Of course, the best solution for surface films is to avoid them by improved specimen preparation and handling procedures or to remove them by low energy ion sputter cleaning, a capability that already exists on some specialized AEMs and one that is likely to become increasingly common. However, the problem remains and it is surprising that surface films have not received more attention with respect to composition determination by energy dispersive X-ray spectrometry (EDS) and electron energy loss spectrometry (EELS).For EDS, an effective first-order correction to remove the contribution of surface films on wedge shaped specimens is to subtract from the spectrum of interest a spectrum obtained under identical conditions (probe current, diffracting conditions, acquisition live time) from a thinner region of the specimen.

Energy-filtered plasmon images of MgAl2O4 implanted with Al+ and Mg+ ions

1995 ◽  
Vol 53 ◽  
pp. 266-267
Author(s):  
N. D. Evans ◽  
J. Bentley ◽  
S. J. Zinkle
Keyword(s):  
Room Temperature ◽  
Analytical Electron Microscopy ◽  
Fusion Reactors ◽  
High Dose ◽  
Phase Identification ◽  
Magnesium Aluminate Spinel ◽  
Dose Irradiation ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss

Magnesium aluminate spinel (MgAl2O4) is a candidate material for specialized applications in proposed fusion reactors, and previously, has been irradiated with Al+ or Mg+ ions to assess the effects of high-dose irradiation. Electron energy-loss spectrometry (EELS) has been used to confirm the identity of metallic aluminum colloids located in the ion-implanted region of the spinel because electron diffraction experiments were inconclusive for phase identification. In the present study, energy-filtered plasmon images of the ionimplanted region have been obtained to reveal this colloid distribution.Following implantation with 2 MeV Al+ ions to a fluence of 3.8 × 1021 ions/m2 at 923 K, or with 2.4 MeV Mg+ to a fluence of 2.8 × 1021 ions/m2 at room temperature, spinel specimens were prepared in cross-section for analytical electron microscopy. Energy-filtered images were obtained using a Philips CM30 microscope with an attached Gatan Imaging Filter. Acquired images were 512 × 512 pixels in size and gain normalized.

Detection limits for Analytical Electron Microscopy with Electron Energy Loss Spectrometry and energy-dispersive x-ray spectrometry

1993 ◽  
Vol 51 ◽  
pp. 594-595
Author(s):  
Dale E. Newbury ◽  
Richard D. Leapman
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Cross Section ◽  
Analytical Electron Microscopy ◽  
Energy Dispersive ◽  
X Ray ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss

The measurement of trace level constituents, arbitrarily defined for this study as concentration levels below 1 atom percent, has always been considered problematic for analytical electron microscopy (AEM) with energy dispersive x-ray spectrometry (EDS) and electron energy loss spectrometry (EELS). In a landmark study of various microanalysis techniques, Wittry evaluated the influence of various instrumental factors (source brightness, detection efficiency, accumulation time) and physical factors (cross section, peak-to-background) upon detection limits. Although the ionization cross section, fluorescence yield, and collection efficiency favor EELS over EDS, the peak-to-background ratio of EELS spectra is much lower than that of EDS spectra, leading Wittry to suggest that the limit of detection should be 0.1 percent for EDS and 1 percent for EELS for practical measurement conditions. Recent developments in parallel detection EELS (PEELS) indicate that a re-evaluation of the situation for trace constituent determination is needed for those elements characterized by "white line" resonance structures at the ionization edge.

Trace Analysis of Nanoscale Materials by Analytical Electron Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
Dale E. Newbury ◽  
Richard D. Leapman
Keyword(s):  
Trace Analysis ◽  
Analytical Electron Microscopy ◽  
Beam Current ◽  
Resonance Structure ◽  
White Line ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Trace Constituents ◽  
Electron Energy Loss ◽  
Microscopic Distribution

ABSTRACTTrace analysis of nanometer-scale objects can be performed with parallel-detection electron energy loss spectrometry in the analytical electron microscope. Spectra are collected in the second difference mode with the beam current chosen to maximize the spectral count rate. Numerous elements can be detected at trace levels below 100 parts per million atomic, including transition metal, alkali metal, alkaline earth, and rare earth elements, provided they have a “white line” resonance structure at the ionization edge. Trace nanoanalysis by AEM/PEELS permits direct examination of the microscopic distribution of trace constituents.

Accurate quantification of lithium in aluminium-lithium alloys with electron energy-loss spectrometry

1989 ◽  
Vol 425 (1868) ◽  
pp. 91-111 ◽  
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Partial Cross Section ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Electron Energy Loss Spectrometry ◽  
Δ Phase ◽  
Extrapolation Scheme ◽  
Electron Energy Loss ◽  
Accurate Quantification

The composition of the Al 3 Li (δ)' metastable precipitation-hardening phase is an important factor in understanding the strengthening behaviour of Al-Li base alloys. The procedure for using electron energy-loss spectrometry in a transmission electron microscope for accurate quantification of the Li content of δ' is established. All factors that can affect the accuracy of the analysis procedure are considered, namely: the specimen preparation, the mode of operation of the microscope, the identification of spectra from through-thickness regions of the specimen, the calibration of the Li / Al partial cross-section ratio, the deconvolution of the spectra and the background extrapolation scheme. The composition of the δ' phase in the temperature range 155-290 °C is determined, and the non-stoichiometry of this phase is clearly shown.

Analytical Electron Microscopy of Precipitates in Ion-Implanted Mgal2O4 Spinel

1994 ◽  
Vol 373 ◽  
Author(s):  
N. D. Evans ◽  
S. J. Zinkle ◽  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Volume Fraction ◽  
Analytical Electron Microscopy ◽  
Metallic Aluminum ◽  
X Ray ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss ◽  
Ion Implanted

AbstractAnalytical electron microscopy (AEM) has been used to investigate precipitates in MgAl2O4 spinel implantated with Al+, Mg+, or Fe2+ ions. Experiments combining diffraction, energy dispersive X-ray spectrometry (EDS), electron energy-loss spectrometry (EELS), and energy-filtered imaging were employed to identify and characterize precipitates observed in the implanted ion region. Diffraction studies suggested these are metallic aluminum colloids, although EELS and energy-filtered images revealed this to be so only for the Al+ and Mg+ implantations, but not for Fe2+ ion implantations. Multiple-least-squares (MLS) fitting of EELS plasmon spectra was employed to quantify the volume fraction of metallic aluminum in the implanted ion region. Energy-filtered plasmon images of the implanted ion region clearly show the colloid distribution in the Al+ and Mg+ implanted spinel. Energy-filtered images from the Fe2+ ion implanted spinel indicate that the features visible in diffraction contrast cannot be associated with either metallic aluminum or iron-rich precipitates.

Tutorial: Tem Specimen Preparation in the Physical Sciencestripod Polishing and Ion Milling

1998 ◽  
Vol 4 (S2) ◽  
pp. 876-877
Author(s):  
Ron Anderson
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Specimen Preparation ◽  
Strategic Choices ◽  
Ion Milling ◽  
Thin Specimen ◽  
The Past ◽  
Analytical Electron ◽  
Preparation Techniques ◽  
Modern Analytical

Over the past few decades, the demands of modern analytical electron microscopy have increased the need for TEM specimen preparation techniques with a minimum of misleading artifacts in terms of chemical microanalysis. At the same time, the demands of modern industrial materials, be they semiconductor, polymeric or composite in nature, call for speed, flexibility and high spatial resolution as well. The response from the electron microscopy community, especially that portion in the private sector, have been to devise (or advocate) radically different forms of TEM thin specimen preparation from that of classic replication, electropolishing and ion thinning.This tutorial sets forth the goals of TEM specimen preparation, and the requirements for a "good" TEM specimen. The strategic choices governing which technique to use for preparing a wide variety of specimens will be covered. A TEM Specimen Preparation Flow Chart will be used to plot a course that makes optimum use of the preparation techniques available as a function of the type of specimen to be prepared.

A library of convergent-beam electron diffraction patterns

1986 ◽  
Vol 44 ◽  
pp. 688-691
Author(s):  
John F. Mansfield
Keyword(s):  
Electron Diffraction ◽  
Materials Science ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Transmission Electron ◽  
Yield Information ◽  
Analytical Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Electron Energy Loss

One of the most important advancements of the transmission electron microscopy (TEM) in recent years has been the development of the analytical electron microscope (AEM). The microanalytical capabilities of AEMs are based on the three major techniques that have been refined in the last decade or so, namely, Convergent Beam Electron Diffraction (CBED), X-ray Energy Dispersive Spectroscopy (XEDS) and Electron Energy Loss Spectroscopy (EELS). Each of these techniques can yield information on the specimen under study that is not obtainable by any other means. However, it is when they are used in concert that they are most powerful. The application of CBED in materials science is not restricted to microanalysis. However, this is the area where it is most frequently employed. It is used specifically to the identification of the lattice-type, point and space group of phases present within a sample. The addition of chemical/elemental information from XEDS or EELS spectra to the diffraction data usually allows unique identification of a phase.

Phase identification in SiC whisker reinforced Al2O3-R2O3-based composites

1992 ◽  
Vol 50 (1) ◽  
pp. 152-153
Author(s):  
C.M. Sung ◽  
K.J. Ostreicher ◽  
M.L. Huckabee ◽  
S.T. Buljan
Keyword(s):  
Analytical Electron Microscopy ◽  
Phase Identification ◽  
Reinforced Composites ◽  
Ion Milling ◽  
X Ray ◽  
Binary Oxides ◽  
Analytical Electron ◽  
The Matrix ◽  
Second Phases ◽  
Convergent Beam

A series of binary oxides and SiC whisker reinforced composites both having a matrix composed of an α-(Al, R)2O3 solid solution (R: rare earth) have been studied by analytical electron microscopy (AEM). The mechanical properties of the composites as well as crystal structure, composition, and defects of both second phases and the matrix were investigated. The formation of various second phases, e.g. garnet, β-Alumina, or perovskite structures in the binary Al2O3-R2O3 and the ternary Al2O3-R2O3-SiC(w) systems are discussed.Sections of the materials having thicknesses of 100 μm - 300 μm were first diamond core drilled. The discs were then polished and dimpled. The final step was ion milling with Ar+ until breakthrough occurred. Samples prepared in this manner were then analyzed using the Philips EM400T AEM. The low-Z energy dispersive X-ray spectroscopy (EDXS) data were obtained and correlated with convergent beam electron diffraction (CBED) patterns to identify phase compositions and structures. The following EDXS parameters were maintained in the analyzed areas: accelerating voltage of 120 keV, sample tilt of 12° and 20% dead time.

Preparation of Backthinned Ceramic Specimens

1985 ◽  
Vol 43 ◽  
pp. 182-183
Author(s):  
A. T. Fisher ◽  
P. Angelini
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Vacuum System ◽  
Back Surface ◽  
Surface Microstructure ◽  
Ion Milling ◽  
Near Surface ◽  
Depth Profiles ◽  
Analytical Electron ◽  
Ion Implanted

Analytical electron microscopy (AEM) of the near surface microstructure of ion implanted ceramics can provide much information about these materials. Backthinning of specimens results in relatively large thin areas for analysis of precipitates, voids, dislocations, depth profiles of implanted species and other features. One of the most critical stages in the backthinning process is the ion milling procedure. Material sputtered during ion milling can redeposit on the back surface thereby contaminating the specimen with impurities such as Fe, Cr, Ni, Mo, Si, etc. These impurities may originate from the specimen, specimen platform and clamping plates, vacuum system, and other components. The contamination may take the form of discrete particles or continuous films [Fig. 1] and compromises many of the compositional and microstructural analyses. A method is being developed to protect the implanted surface by coating it with NaCl prior to backthinning. Impurities which deposit on the continuous NaCl film during ion milling are removed by immersing the specimen in water and floating the contaminants from the specimen as the salt dissolves.

Preparation and characterization of thin films of carbon nitride

1995 ◽  
Vol 53 ◽  
pp. 104-105
Author(s):  
L. Wan ◽  
R. F. Egerton
Keyword(s):  
Carbon Nitride ◽  
Arc Discharge ◽  
Ion Beam ◽  
Chemical Vapor ◽  
Reactive Sputtering ◽  
Vacuum Arc ◽  
Specimen Preparation ◽  
Bonding Structure ◽  
Electron Energy Loss

INTRODUCTION Recently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4 are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNX films deposited by two different methods.SPECIMEN PREPARATION Specimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.

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