scholarly journals Transmission Electron Microscopy Study In-Situ of Radiation-Induced Defects in Copper at Elevated Temperatures

1996 ◽  
Vol 439 ◽  
Author(s):  
T. L. Daulton ◽  
M. A. Kirk ◽  
L. E. Rehn
Keyword(s):  
Point Defects ◽  
Elevated Temperatures ◽  
Defect Density ◽  
Microscopy Study ◽  
High Energy ◽  
Dislocation Loops ◽  
Contrast Imaging ◽  
High Concentration ◽  
Transmission Electron

AbstractNeutrons and high-energy ions incident upon a solid can initiate a displacement collision cascade of lattice atoms resulting in localized regions within the solid containing a high concentration of interstitial and vacancy point defects. These point defects can collapse into various types of dislocation loops and stacking fault tetrahedra (SFT) large enough that their lattice strain fields are visible under diffraction-contrast imaging using a Transmission Electron Microscope (TEM). The basic mechanisms driving the collapse of point defects produced in collision cascades is investigated in situ with TEM for fcc-Cu irradiated with heavy (100 keV Kr) ions at elevated temperature. The isothermal stability of these clusters is also examined in situ.Areal defect yields were observed to decrease abruptly for temperatures greater than 300°C. This decrease in defect yield is attributed to a proportional decrease in the probability of collapse of point defects into clusters. The evolution of the defect density under isothermal conditions appears to be influenced by three different rate processes active in the decline of the total defect density. These rate constants can be attributed to differences in the stability of various types of defect clusters and to different loss mechanisms. Based upon observed stabilities, estimations for the average binding enthalpies of vacancies to SFT are calculated for copper.

In situ annealing of aluminum ion-implanted with molybdenum

1983 ◽  
Vol 41 ◽  
pp. 260-261
Author(s):  
J. Bentley ◽  
L. D. Stephenson ◽  
R. B. Benson ◽  
P. A. Parrish
Keyword(s):  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Naval Research ◽  
Dislocation Network ◽  
Dislocation Loops ◽  
High Concentration ◽  
Aluminum Ion ◽  
Ion Implanted

As part of an analytical electron microscopy study of aluminum ion-implanted with molybdenum, in situ annealing experiments have been performed to better understand the phase transformation mechanisms in material with a peak molybdenum content of approximately 11 at. % Mo. Ion implantations were performed at the Naval Research Laboratory on electropolished coupons 38 × 28 × 0.5 mm of 99.999% Al with 0.5 mm grain size. A dual energy implant schedule of 1.12 × 1020 ions/m2 at 50 keV. plus 1.24 × 1020 ions/m2 at 110 keV was employed. The TEM specimens were prepared by electrodischarge machining 3-mm diameter disks from the implanted coupons and backthinning by electropolishing. In situ annealing was performed in a Philips EM 400T/FEG with the use of a Philips single-tilt heating holder. Videotape recordings were made from the TEM fluorescent viewing screen in the tilted position.A high concentration of small dislocation loops and possibly a tangled dislocation network were present in the as-implanted material. No precipitates were observed; this is consistent with a supersaturated solid solution.

scholarly journals In situ electron microscopy study of structural transformations in 2D CoSe2

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Dnyaneshwar S. Gavhane ◽  
Heleen van Gog ◽  
Balu Thombare ◽  
Gaurav Lole ◽  
L. Christiaan Post ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Elevated Temperatures ◽  
2D Materials ◽  
Microscopy Study ◽  
Structural Transformations ◽  
Electron Microscopy Study ◽  
Thermally Induced ◽  
Transmission Electron ◽  
Transformation Processes

AbstractThermally induced structural transformation of 2D materials opens unique avenues for generating other 2D materials by physical methods. Imaging these transitions in real time provides insight into synthesis routes and property tuning. We have used in situ transmission electron microscopy (TEM) to follow thermally induced structural transformations in layered CoSe2. Three transformation processes are observed: orthorhombic to cubic-CoSe2, cubic-CoSe2 to hexagonal-CoSe, and hexagonal to tetragonal-CoSe. In particular, the unit-cell-thick orthorhombic structure of CoSe2 transforms into cubic-CoSe2 via rearrangement of lattice atoms. Cubic-CoSe2 transforms to hexagonal-CoSe at elevated temperatures through the removal of chalcogen atoms. All nanosheets transform to basal-plane-oriented hexagonal 2D CoSe. Finally, the hexagonal to tetragonal transformation in CoSe is a rapid process wherein the layered morphology of hexagonal-CoSe is broken and islands of tetragonal-CoSe are formed. Our results provide nanoscopic insights into the transformation processes of 2D CoSe2 which can be used to generate these intriguing 2D materials and to tune their properties by modifying their structures for electro-catalytic and electronic applications.

scholarly journals Transmission Electron Microscopy Study of Cascade Collapse in Copper During in- Situ Ion- Irradiation at Elevated Temperatures

1997 ◽  
Vol 504 ◽  
Author(s):  
T. L. Daulton ◽  
M. A. Kirk ◽  
L. E. Rehn
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Defect Production ◽  
Transmission Electron ◽  
Defect Microstructures ◽  
Proportional Decrease

ABSTRACTThe basic mechanisms driving the collapse of point defects produced in collision cascades are investigated by transmission electron microscope (TEM) characterization of defect microstructures produced in fcc-Cu irradiated with low-fluences of heavy (100 keV Kr) ions at elevated temperature (23–600°C). Areal defect yields are determined from direct TEM observation of the total defect production integrated over the duration of the in-situ ion-irradiation. They are unequivocally demonstrated to decrease with increasing lattice temperature. This decrease in defect yield indicates a proportional decrease in the probability of collapse of cascade regions into defects of size where visible contrast is produced in a TEM.

In situ Transmission Electron Microscopy Study of the growth of Ni Nanoparticles on Amorphous Carbon and of the Graphitization of the Support in the Presence of Hydrogen

2005 ◽  
Vol 20 (7) ◽  
pp. 1837-1843 ◽  
Author(s):  
R. Anton
Keyword(s):  
Amorphous Carbon ◽  
Reaction Front ◽  
Elevated Temperatures ◽  
Carbon Support ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Concomitant Increase ◽  
Transmission Electron Microscopy Study ◽  
Transmission Electron

In a specially equipped transmission electron microscope (TEM), Ni particles were vapor deposited onto thin films of amorphous carbon (a-C), and subsequent reactions with the carbon support were observed at elevated temperatures. Particles deposited at temperatures around 370 °C developed a graphite shell at above 600 °C and subsequently spread and graphitized the substrate. This activity was enhanced by hydrogen. The speed of graphitization significantly increased during spreading of the metal, which is attributed to the concomitant increase of the length of the reaction front, as well as to a purifying effect of hydrogen. It is concluded that the driving force for spreading of the Ni is the interdiffusion and catalytic conversion of carbonto graphite at the reaction front. Particles deposited at 500 °C remained inactive at670 °C. This is probably due to the formation of a rather stable carbidic or graphitic interlayer during deposition.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

Study of dislocation loops in Arsenic-Rich as-grown GaAs

1987 ◽  
Vol 45 ◽  
pp. 350-351
Author(s):  
Byung-Teak Lee
Keyword(s):  
Point Defects ◽  
Electronic Devices ◽  
Arsenic Concentration ◽  
Stoichiometric Compound ◽  
Dislocation Loops ◽  
Gaas Crystal ◽  
Ion Milling ◽  
Transmission Electron ◽  
Arsenic Source ◽  
High Arsenic

Grown-in dislocations in GaAs have been a major obstacle in utilizing this material for the potential electronic devices. Although it has been proposed in many reports that supersaturation of point defects can generate dislocation loops in growing crystals and can be a main formation mechanism of grown-in dislocations, there are very few reports on either the observation or the structural analysis of the stoichiometry-generated loops. In this work, dislocation loops in an arsenic-rich GaAs crystal have been studied by transmission electron microscopy.The single crystal with high arsenic concentration was grown using the Horizontal Bridgman method. The arsenic source temperature during the crystal growth was about 630°C whereas 617±1°C is normally believed to be optimum one to grow a stoichiometric compound. Samples with various orientations were prepared either by chemical thinning or ion milling and examined in both a JEOL JEM 200CX and a Siemens Elmiskop 102.

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

Electron and ion irradiation-induced dissolution of mechanical twins in the intermetalic U3Si: An in situ HVEM study

1989 ◽  
Vol 47 ◽  
pp. 652-653
Author(s):  
Charles W. Allen ◽  
Robert C. Birtcher
Keyword(s):  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Heavy Ion ◽  
High Energy ◽  
Mechanical Twinning ◽  
In Situ Experiments

The uranium silicides, including U3Si, are under study as candidate low enrichment nuclear fuels. Ion beam simulations of the in-reactor behavior of such materials are performed because a similar damage structure can be produced in hours by energetic heavy ions which requires years in actual reactor tests. This contribution treats one aspect of the microstructural behavior of U3Si under high energy electron irradiation and low dose energetic heavy ion irradiation and is based on in situ experiments, performed at the HVEM-Tandem User Facility at Argonne National Laboratory. This Facility interfaces a 2 MV Tandem ion accelerator and a 0.6 MV ion implanter to a 1.2 MeV AEI high voltage electron microscope, which allows a wide variety of in situ ion beam experiments to be performed with simultaneous irradiation and electron microscopy or diffraction.At elevated temperatures, U3Si exhibits the ordered AuCu3 structure. On cooling below 1058 K, the intermetallic transforms, evidently martensitically, to a body-centered tetragonal structure (alternatively, the structure may be described as face-centered tetragonal, which would be fcc except for a 1 pet tetragonal distortion). Mechanical twinning accompanies the transformation; however, diferences between electron diffraction patterns from twinned and non-twinned martensite plates could not be distinguished.

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