Minimizing Transmission Electron Microscopy Beam Damage during the Study of Surface Reactions on Sodium Chloride

1998 ◽  
Vol 4 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Heather C. Allen ◽  
Martha L. Mecartney ◽  
John C. Hemminger
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Water Vapor ◽  
Sodium Chloride ◽  
Single Crystals ◽  
Alkali Halide ◽  
Surface Reactions ◽  
Transmission Electron ◽  
Alkali Halide Crystals ◽  
Beam Damage

Electron beam damage is a significant limitation for transmission electron microscopy (TEM) studies of beam-sensitive samples. An approach for studying surface reactions on alkali halide crystals using 200 kV TEM is presented. Experiments were designed to monitor the reaction of NaCl crystals with HNO3 gas followed by water vapor to form solid NaNO3. During beam damage experiments, TEM micrographs record structural changes to both NaCl and NaNO3, including dislocation loops, void formation, and decomposition. Sample decomposition can be successfully minimized by a combination of commonly used techniques: (1) focusing the beam adjacent to the area of interest, (2) lowering the electron density, (3) choosing to image larger (micrometer- versus submicrometer-sized) alkali halide crystals, and (4) lowering temperature by the use of a liquid nitrogen cooling stage. From these results, additional studies were designed that monitored sequential experiments. Sensitive micrometer-sized sodium chloride single crystals before and after exposure to nitric acid vapor and water vapor and the subsequent growth of submicrometer-sized sodium nitrate single crystals could then be successfully imaged using TEM.

Scanning Transmission Electron Microscopy Of Polymer Single Crystals

1977 ◽  
Vol 35 ◽  
pp. 172-173
Author(s):  
S. J. Krause ◽  
L. F. Allard ◽  
W. C. Bigelow
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Scanning Transmission Electron Microscopy ◽  
Incident Beam ◽  
Photographic Recording ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Beam Damage

Scanning transmission electron microscopy (STEM) has several advantages over conventional transmission electron microscopy (CTEM) for studying the structure of polymer single crystals. A major limitation in the electron microscopy of polymer single crystals is the rapid loss of diffraction contrast due to destruction of crystallinity by beam-induced cross-linking and/or chain scission. Electronic signal amplification, which is inherent in the STEM image forming system, allows images to be formed at lower incident beam dosages than required for photographic recording in the CTEM. This lowers the beam damage rate and routinely permits recording of bright field, dark field, and electron diffraction sequences, or alternatively, single images at high magnification for high resolution.An SEM operated in the STEM mode at voltages in the range from 20 to 50 KV will give good images of single crystals at magnifications up to 10,000X. An STEM operated at 100 KV with cold stage techniques further improves the imaging capabilities, since beam damage is reduced by 5 to 10 times with an increase in accelerating voltage and lower sample temperatures.1

Effects of High-Energy Ions on Synthetic Quartz

1972 ◽  
Vol 30 ◽  
pp. 544-545
Author(s):  
Joseph J. Comer ◽  
Charles Bergeron ◽  
Lester F. Lowe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Energy ◽  
Transmission Electron ◽  
Kikuchi Lines ◽  
High Energy Ions ◽  
Diffraction Patterns ◽  
Dauphiné Twinning ◽  
Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

Transmission Electron Microscopy study of Bi-based superconducting phases

1990 ◽  
Vol 48 (4) ◽  
pp. 50-51
Author(s):  
J.G. Wen ◽  
K.K. Fung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Space Groups ◽  
Superconducting Phases ◽  
Ceramic Samples ◽  
Transmission Electron ◽  
Modulated Structures

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.

scholarly journals Identification of Faults in Asbestos Minerals and Application to Pollution Studies

1976 ◽  
Vol 34 ◽  
pp. 616-617
Author(s):  
K. Seshan ◽  
H.-R. Wenk
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Twin Plane ◽  
Fibre Axis ◽  
Fibre Structure ◽  
Asbestos Fibre ◽  
Fibre Texture ◽  
Transmission Electron ◽  
Diffraction Patterns

Asbestos fibre texture occurs in various mineral groups (e.g. chrysotile, crocidolite, tremolite, grunerite, tourmaline) and it has been established that at least chrysotile is carcinogenic. We are investigating various aspects of the asbestos structure, with transmission electron microscopy (TEM) (1) in order to develop methods for unequivocal asbestos identification using minute samples and also to determine defects responsible for the fibre structure in these minerals which often occur as large, we 11-developed single crystals.In order to do this, we have started by investigating clinoamphibole asbestos such as tremolite Ca2Mg5[Si8O22] (OH, F)2 and crocidolite Na2 (Mg, Al, Fe3+, Fe2+) (Si8O22) (OH, F )2 , from California localities. In crocidoli te - asbestos we observed a high density of very narrow microtwins parallel to the fibre axis [001] (Fig. 1). They are often only 50-100Å wide. Diffraction patterns display the typical twin arrangement of spots and although preliminary contrast experiments are not yet conclusive the twin plane appears to be (100).

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