Onion-Like Nanoscale Structures and Fullerene-Type Cages Formed by Electron Irradiation of Turbostratic Bx.C1-x (x<0.2)

1997 ◽  
Vol 481 ◽  
Author(s):  
D. Golberg ◽  
Y. Bando ◽  
K. Kurashima ◽  
T. Sasaki
Keyword(s):  
Electron Irradiation ◽  
Soap Bubble ◽  
Electron Dose ◽  
Nanoscale Structures ◽  
Linear Dimensions ◽  
Resolution Electron ◽  
Continuous Bending ◽  
High Resolution Electron Microscope ◽  
Electron Energy Loss ◽  
Intense Electron

ABSTRACTFlakes of CVD grown BxC1-x, (x<0.2) films were exposed to intense electron irradiation (flux density up to ∼100 A/cm2) in a 300 kV high resolution electron microscope equipped with a field emission gun. The starting flakes revealed a turbostratic BxC1-x structure. The composition of the starting materials and irradiated products was determined by using electron energy loss spectroscopy (EELS). Depending on the electron dose applied, irradiation of the turbostratic material led to formation of soap-bubble-like irregularly-shaped objects (linear dimensions of ∼2–5 nm), onion- and semi-onion-like structures (d∼10nm), nested fullerenes (3–14 shells) and elementary fullerene-type cages (d∼0.7 nm). It is thought that these curled and closed nanostructures arise from a continuous bending of the hexagonal Bx C1-x sheets under electron irradiation. Finally, some possible structural models of BxC1-x fullerenes are considered.

The Apex Structure of Co-Produced Helical Boron Nitride and Carbon Cones

1999 ◽  
Vol 5 (S2) ◽  
pp. 816-817
Author(s):  
L Bourgeois ◽  
Y. Bando ◽  
K. Kurashima ◽  
T. Sato
Keyword(s):  
Boron Nitride ◽  
Topological Defect ◽  
Hexagonal Boron Nitride ◽  
Layered Compounds ◽  
Hexagonal Ring ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Cone Apex ◽  
High Resolution Electron Microscope ◽  
Electron Energy Loss

Conical whiskers of layered compounds such as graphite and hexagonal boron nitride (h-BN)2 are interesting materials because their conical morphology results from the introduction of a local topological defect at the cone apex. In the honeycomb array characteristic of graphite and h-BN basal planes, this topological defect is thought to be a non-hexagonal ring (e.g. a pentagon or a square). These defects are known to form the basis of curved nanostructures like fullerenes and buckytubes. Therefore a comparison of their occurrence in two systems known to harbour nanostructures is worthy of study.The defect structure at the apex of co-produced carbon and boron nitride whiskers was investigated by analytical transmission electron microscopy (TEM). The instrument used was a field-emission JEM3000F high-resolution electron microscope, equipped with a parallel electron energy loss spectrometer (EELS).

Dynamic TEM Observation on Oxide Glass Materials

1990 ◽  
Vol 183 ◽  
Author(s):  
Sumio Iijima
Keyword(s):  
Electron Beam Irradiation ◽  
Amorphous Film ◽  
Oxide Glass ◽  
Model Structure ◽  
Resolution Electron ◽  
Atom Migration ◽  
Intense Electron Beam ◽  
High Resolution Electron Microscope ◽  
Intense Electron ◽  
Image Simulations

AbstractIntensity fluctuation in high resolution electron microscope (HREM) images of amorphous Tl-Ba-Ca-Cu-O oxide films is observed. The fluctuation with a frequency of few tens of Hertz and an amplitude of about 0.3nm, occurs under an intense electron beam irradiation. It is shown experimentally that atom migration in the films is responsible for the fluctuations. The result is also supported by computer image simulations on a model structure for amorphous film.

HREM In-Situ Studies of Electron Irradiation Effects in Oxides

1988 ◽  
Vol 100 ◽  
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett ◽  
J. W. Strane ◽  
B. W. Wessels ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Point Of View ◽  
Irradiation Damage ◽  
Original Material ◽  
Irradiation Effects ◽  
Resolution Electron ◽  
Wide Range ◽  
Electronic Irradiation ◽  
High Resolution Electron Microscope

ABSTRACTHigh resolution electron microscope (HREM) studies provide the ability to study desorption and sputtering from the perspective of the analysis of the resultant materials, their structure, composition and atomic registry (orientation with respect to the original,material and the irradiation). This is a neglected facet of surface irradiation effects research, yet it is the most important from the technological point of view. In the current study, surface electron irradiation processes in oxides were studied in-situ in a Hitachi H-9000 HREM operated at incident electron energies of 100–300 keV. It was found that a wide range of processes occur in the HREM which are dependent on the energy and flux of the incident electrons and on the material properties. Both ballistic and electronic irradiation damage was observed and the material responses included surface sputtering, amorphisation, chemical disordering, desorption of O and metal surface layer creation, surface roughening and bulk defect creation.

Formation of a Ni3O4 Spinel Phase on the Surface of NiO During Electron Irradiation

1988 ◽  
Vol 129 ◽  
Author(s):  
Mary I. Buckett ◽  
L. D. Marks
Keyword(s):  
Surface Science ◽  
Electron Irradiation ◽  
Structural Changes ◽  
Science Studies ◽  
Spinel Phase ◽  
Preparation Conditions ◽  
Variable Voltage ◽  
Resolution Electron ◽  
High Resolution Electron Microscope

ABSTRACTStructural changes occurring at the surface of NiO during electron irradiation were examined in-situ with a variable voltage high resolution electron microscope. The interaction of the specimen with the electron beam was found to be highly dependent on the state of the surface prior to irradiation. It was observed that by varying the sample preparation conditions, the Ni on the surface of NiO could either be oxidized to Ni304 spinel phase or reduced to islands of metallic Ni. The formation of the Ni3O4 spinel phase is in agreement with previous surface science studies, where chemical shift information identified the presence of Ni3+ species at the surface. This has previously been interpreted as the formation of Ni203

HREM Observations of Deformation Recovery on and Near Surfaces of Eu2O3

1990 ◽  
Vol 48 (1) ◽  
pp. 344-345
Author(s):  
X.G. Ning ◽  
H.Q. Ye
Keyword(s):  
Surface Science ◽  
Electron Irradiation ◽  
Surface Deformation ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
The Right ◽  
Deformation Recovery

Profile imaging technigue has been achieved very much in the field of surface science since it was first proposed. This work will show the deformation recovery on and near the surfaces of Eu2O3 under electron irradiation. The experiment was carried out in a JEOL-200CX high-resolution electron microscope. The Eu2O3 phase has a complex cubic structure with a=1.087 nm. A projected unit cell has been marked in Fig. la. It has been indicated that only Eu3+ ions , which are located in f.c.c. sublattice, appeared in HR images under certain defocus and in the thin areas of specimen. The structural character of Eu2O3 shown by HR images may be analyzed based upon comparing with that of simple f.c.c. structure.It can be seen from Fig. la that the surfaces of Eu2O3 are clean and Eu3+ ions on the (111) surfaces S1 and S2 moved /12 towards to the right (it is actually surface stacking fault). In Fig.lb the stacking fault on S2 was removed under electron irradiation but remained on S1. The stacking fault energy of Eu2O3 is high in the bulk. From Fig.l it can be known that the stacking fault energy may become lower on the (111) surface due to less constrained factors there. This kind of surface stacking fault is related to surface partial dislocations, and both of them may act as the main forms of surface deformation under electron irradiation.

Combined Hrem and Eels Studies of the Electron Beam Induced Reduction of Maximal-Valence Transition-Metal Oxides.

1986 ◽  
Vol 74 ◽  
Author(s):  
Neil J. Long ◽  
Amanda K. Petford-Long
Keyword(s):  
Transition Metal Oxides ◽  
High Resolution Electron Microscopy ◽  
Critical Value ◽  
Electron Gun ◽  
Hole Drilling ◽  
Electron Dose ◽  
Valence Transition ◽  
Resolution Electron ◽  
Drill Holes ◽  
Electron Energy Loss

AbstractHigh resolution electron microscopy has been used in conjunction with electron energy loss spectroscopy to follow the beam-induced reduction of WO3, V2 O5 and CuO, all of which are maximal valence oxides. All three oxides underwent reduction, although there are differences in the reduction pathway: WO3 is reduced directly to the metal by loss of oxygen from the surface layers; CuO is reduced to the metal via at least two intermediate oxides (Cu4 O3 and Cu2O); and V2 05 forms a reduced oxide (possibly V6 O13) and then remains stable. It was possible to drill holes in V2O5 with an intense, small electron probe (using a field-emission electron gun) provided the sample had previously only been exposed to an electron dose below a critical value (<108 e/nm2). Preliminary doses higher than this critical value rendered the oxide immune to hole drilling (but not to a subsequent reduction to the stable oxide mentioned above), suggesting that holes can only be drilled while the material retains the original V2O5 structure.

Surface Structures and Rearrangements in Oxides

1990 ◽  
Vol 183 ◽  
Author(s):  
M. R. Mccartney ◽  
David J. Smith
Keyword(s):  
High Resolution ◽  
Electron Irradiation ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Dose ◽  
Dose Rates ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Current Densities ◽  
Electron Microscopes

AbstractElectron-beam-induced surface reactions and rearrangements have been observed for a number of oxides including MgO, TiO2, SrTiO3 and SnO2 using conventional and ultra-high-vacuum high-resolution electron microscopes. Electron irradiation of TiO2 resulted in a variety of effects including reduction, re-oxidation and amorphization. SnO2 was observed to form facets readily during high-resolution imaging but it was stable against reduction except when exposed to extreme current densities which caused the formation of metallic tin crystals. Electron irradiation of MgO under UHV conditions resulted in the formation of facetted pits. The surfaces of SrTiO3 were stable for moderate electron dose rates but rapidly amorphized when irradiated at extreme current densities.

First Results of a Monochromized 200KV TEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 1130-1131 ◽  
Author(s):  
P.C. Tiemeijer ◽  
J.H.A. van Lin ◽  
A.F. de Jong
Keyword(s):  
High Frequency ◽  
High Tension ◽  
Resolution Electron ◽  
First Results ◽  
High Resolution Electron Microscope ◽  
Frequency Generator ◽  
Electrical Damping ◽  
The University ◽  
Electron Energy Loss ◽  
High Frequency Generator

FEI is currently finishing the construction of a monochromized 200kV (S)TEM which aims at 0.1 eV resolution in Electron Energy Loss Spectroscopy (EELS). This requires improvement of the 200kV supply, improvement of the EELS spectrometer, and the incorporation of an electron beam monochromator. This microscope will be delivered to the National Centre for High Resolution Electron Microscope at the University of Delft.The present 200kV supply contributes 0.2 eV to the energy resolution because of its instabilities, drift and high frequency ripple. in order to reduce this, mechanical as well as electrical damping elements are being added, and sources of cross-talk between the high frequency generator and the high tension are eliminated. in this paper, we present preliminary results obtained with a standard 200kV supply; we expect to present results of the improved 200kV supply at the conference.The resolution of a present-day standard 200kV spectrometer is now typically 0.4 eV. in order to improve on this, GATAN has developed a HR-EELS spectrometer for the monochromized TEM.

Electron microscopy and diffraction studies of polyimides

1983 ◽  
Vol 41 ◽  
pp. 28-29
Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Features ◽  
Inert Atmosphere ◽  
Polyimide Films ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Sign in / Sign up

Export Citation Format

Share Document