Overcoming the problems of high-resolution transmission electron microscopy of biogenic aragonite

1990 ◽  
Vol 54 (377) ◽  
pp. 589-592 ◽  
Author(s):  
S. E. Ness ◽  
D. W. Haywick ◽  
C. Cuff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Carbonate Minerals ◽  
Biogenic Carbonate ◽  
Transmission Electron ◽  
Before And After ◽  
Diffraction Patterns ◽  
Exposure Technique

AbstractHigh-resolution transmission electron microscopy of biogenic carbonate minerals is hampered by a lack of stability during exposure to the electron beam. However, aragonite in bivalve shells may be successfully imaged using a modification of the ‘minimal-exposure technique’ of Williams and Fisher (1970). Diffraction patterns taken before and after beam exposure indicate that the aragonite remained stable during imaging. The procedure described here should prove useful for further studies of the ultrastructure and/or the diagenesis of biogenic carbonate minerals.

Quasicrystal structures studied by high-resolution transmission electron microscopy

2000 ◽  
Vol 215 (10) ◽  
Author(s):  
Conradin Beeli
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Structural Investigations ◽  
Decagonal Quasicrystals ◽  
Transmission Electron ◽  
The Difference ◽  
Diffraction Patterns ◽  
Special Points

Structural investigations, using a transmission electron microscope (TEM), have been highly beneficial for the analysis of icosahedral and decagonal quasicrystals. Many structural properties of quasicrystals can be recognized and quantified by electron diffraction patterns alone. Nevertheless, a much more complete understanding of the real structure of quasicrystals can be achieved by the analysis of high-resolution transmission electron microscopy (HRTEM) images. Compared to diffraction-based techniques, HRTEM offers several advantages, however, special points which must be considered in the interpretation of HRTEM images will be discussed.For the case of 2-dimensional quasicrystals, e.g. the decagonal phases, HRTEM images can directly reveal the (projected) atomic structure as well as the long-range translational order. This is possible because 2-dimensional quasicrystals are periodic along one direction and the atoms thus form periodic atom columns as in crystalline materials. Therefore, the imaging theory established for crystals can similarly be applied to electron micrographs of 2-dimensional quasicrystals taken with the electron beam parallel to the unique periodic axis. It is evident, that possible limitations due to projection effects along the electron beam direction have to be considered in the interpretation of the images. HRTEM images of decagonal quasicrystals have frequently been employed to differentiate between disorder and order, i.e., to infer the difference between a random and perfect quasiperiodic tiling, respectively.

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.

Characterization of Al2O3 in High-Strength Mo Alloy Sheets by High-Resolution Transmission Electron Microscopy

2016 ◽  
Vol 22 (1) ◽  
pp. 122-130 ◽  
Author(s):  
Yucheng Zhou ◽  
Yimin Gao ◽  
Shizhong Wei ◽  
Yajie Hu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
High Resolution ◽  
Boundary Migration ◽  
Recrystallization Temperature ◽  
Rolled Sheet ◽  
Transmission Electron ◽  
Diffraction Patterns

AbstractA novel type of alumina (Al2O3)-doped molybdenum (Mo) alloy sheet was prepared by a hydrothermal method and a subsequent powder metallurgy process. Then the characterization of α-Al2O3 was investigated using high-resolution transmission electron microscopy as the research focus. The tensile strength of the Al2O3-doped Mo sheet is 43–85% higher than that of the pure Mo sheet, a very obvious reinforcement effect. The sub-micron and nanometer-scale Al2O3 particles can increase the recrystallization temperature by hindering grain boundary migration and improve the tensile strength by effectively blocking the motion of the dislocations. The Al2O3 particles have a good bond with the Mo matrix and there exists an amorphous transition layer at the interface between Al2O3 particles and the Mo matrix in the as-rolled sheet. The sub-structure of α-Al2O3 is characterized by a number of nanograins in the $\left[ {2\bar{2}1} \right]$ direction. Lastly, a new computer-based method for indexing diffraction patterns of the hexagonal system is introduced, with 16 types of diffraction patterns of α-Al2O3 indexed.

Direct Observation of Defect Motion in Silicon By High-Resolution Transmission Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 358-359
Author(s):  
M. A. Parker ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Crystal Defects ◽  
Incident Electron Beam ◽  
Transmission Electron ◽  
Heating Effects ◽  
Electron Beam Heating

Observations of defect motion by high resolution transmission electron microscopy (HRTEM) are rare. Unfortunately, the application of this technique has been limited to a few unique materials, those that can obtain sufficient thermal energy for the initiation of atomic motion through the heating effects of the incident electron beam. In earlier work, it was speculated that events such as the motion of crystal defects, observed in cadmium telluride (CdTe) with the electron beam heating method, might become evident in materials such as silicon (Si) if only sufficiently high temperatures could be achieved (∼ 600°C) in-situ.A silicon specimen with a suitable population of defects was chosen for examination; it consisted of a cross-section of.3 μ ﹛100﹜ silicon on ﹛1102﹜ sapphire (SOS from Union Carbide) which was implant amorphized by 28Si+ ion implantation at an energy of ∼ 170keV.

scholarly journals Odd electron diffraction patterns in silicon nanowires and silicon thin films explained by microtwins and nanotwins

2009 ◽  
Vol 42 (2) ◽  
pp. 242-252 ◽  
Author(s):  
Cyril Cayron ◽  
Martien Den Hertog ◽  
Laurence Latu-Romain ◽  
Céline Mouchet ◽  
Christopher Secouard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Silicon Nanowires ◽  
Si Nanowires ◽  
Silicon Thin Films ◽  
Transmission Electron ◽  
Diffraction Patterns

Odd electron diffraction patterns (EDPs) have been obtained by transmission electron microscopy (TEM) on silicon nanowires grownviathe vapour–liquid–solid method and on silicon thin films deposited by electron beam evaporation. Many explanations have been given in the past, without consensus among the scientific community: size artifacts, twinning artifacts or, more widely accepted, the existence of new hexagonal Si phases. In order to resolve this issue, the microstructures of Si nanowires and Si thin films have been characterized by TEM, high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning transmission electron microscopy. Despite the differences in the geometries and elaboration processes, the EDPs of the materials show great similarities. The different hypotheses reported in the literature have been investigated. It was found that the positions of the diffraction spots in the EDPs could be reproduced by simulating a hexagonal structure withc/a= 12(2/3)1/2, but the intensities in many EDPs remained unexplained. Finally, it was established that all the experimental data,i.e.EDPs and HRTEM images, agree with a classical cubic silicon structure containing two microstructural defects: (i) overlapping Σ3 microtwins which induce extra spots by double diffraction, and (ii) nanotwins which induce extra spots as a result of streaking effects. It is concluded that there is no hexagonal phase in the Si nanowires and the Si thin films presented in this work.

Superposition twinning supported by texture in ZnO nanospikes

2013 ◽  
Vol 46 (2) ◽  
pp. 396-403 ◽  
Author(s):  
Viktor Hrkac ◽  
Lorenz Kienle ◽  
Sören Kaps ◽  
Andriy Lotnyk ◽  
Yogendra Kumar Mishra ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Structural Feature ◽  
Multiple Scattering ◽  
Simulated Data ◽  
Rapid Synthesis ◽  
Transmission Electron ◽  
Specific Morphology ◽  
Diffraction Patterns

The morphology and real structure of wurtzite-type ZnO nanospikes grown by the recently introduced flame transport synthesis have been examined by means of advanced transmission electron microscopy (TEM). The rapid synthesis produces nanospikes showing a well defined texture which restricts TEM experiments to a preferred viewing direction of [2 {\overline 1}{\overline 1}3]. Forced by the specific morphology, all of the observed nanospikes show a complicated superposition of twinned domains as an intrinsic real structural feature. The high-resolution contrasts are characterized by lamellar fringes parallel to the (1 {\overline 1} 0 {\overline 1}) planes, and the quasi-kinematic diffraction patterns contain satellite peaks based on multiple scattering. All these phenomena can be interpreted by comparison of experimental and simulated data relying on a supercell approach.

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