Direct Imaging of the Atomic Structure and Chemistry of Defects and Interfaces by Z-Contrast Stem

1989 ◽  
Vol 169 ◽  
Author(s):  
S. J. Pennycook ◽  
M. F. Chisholm ◽  
D. E. Jesson ◽  
D. P. Norton ◽  
J. W. Mccamy ◽  
...  
Keyword(s):  
Critical Currents ◽  
Atomic Scale ◽  
Structural Defects ◽  
New Approach ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Resolution Imaging ◽  
Film Substrate ◽  
Z Contrast

AbstractZ-contrast scanning transmission electron microscopy (STEM) is a fundamentally new approach to high-resolution imaging which provides unambiguous, compositionally sensitive images on the atomic scale. Such images are intuitively interpretable, even in thick regions of the sample, tremendously simplifying determination of the structure and chemistry of defects and interfaces. To illustrate this, examples are presented of commonly observed planar defects in laser-ablated thin films of YBa2Cu3O7-x. Film/substrate interfaces are shown to be chemically diffuse on the atomic scale and steps or undulations in the substrate need not result in defects in the film. Low-angle grain boundaries are found to be chemically clean, the drastic reductions in critical currents with tilt angle being due to the array of intrinsic structural defects comprising the boundary.

Analysis of Nanometer Sized Pyrogenic Particles by Scanning Transmission Electron Microscopy

1995 ◽  
Vol 53 ◽  
pp. 218-219
Author(s):  
DJ Wallis ◽  
ND Browning ◽  
CM Megaridis
Keyword(s):  
Operating Conditions ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Chemical Mechanisms ◽  
Transmission Electron ◽  
Angle Scattering ◽  
Scanning Transmission ◽  
Z Contrast ◽  
Physical And Chemical ◽  
Electron Energy Loss

Iron is a ubiquitous element on the earth's surface, and is thus involved in most naturally occurring fires. Iron organometalic compounds have also been known to suppress carbonaceous soot emissions under certain operating conditions of practical combustors. In order to unravel the physical and chemical mechanisms of influence, of iron on the emission of carbonaceous pyrogenic particles, finescale characterization techniques need to be implemented.The combined techniques of Z-contrast imaging and electron energy loss spectroscopy (EELS) in a VG HB-501 dedicated STEM are ideally suited to study such a system. The sensitivity of the Z-contrast imaging technique to high-Z materials makes it ideal for location of the iron particles within the much lower atomic number matrix. As only the high-angle scattering is used in the image formation, EELS can be performed simultaneously from a position defined in the image. This accurate positioning of the probe by the Z-contrast image permits both compositional and bonding information to be obtained with a spatial resolution approaching the atomic scale.

Atomic Structure of La067Ca0.33MnO3 Thin Films on LaAlO3

2000 ◽  
Vol 6 (S2) ◽  
pp. 402-403
Author(s):  
H-J. Gao ◽  
C.L. Chen ◽  
X. Fan ◽  
M. Kim ◽  
S.Y. Chen ◽  
...  
Keyword(s):  
Thin Films ◽  
Atomic Structure ◽  
Perovskite Manganites ◽  
X Ray Diffraction ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Film Substrate ◽  
Z Contrast ◽  
Electron Energy Loss

Thin films of doped perovskite manganites of the type R1-X AxMnO3-y are currently become the focus of intense theoretical and experimental research due to their promising technological implications. However, the microstructure of the film and the interface structure at the atomic level remains unclear. In this report, we will present the atomic structure of the film/substrate interface and the microstructure of the film using a combination of transmission electron microscopy (TEM), Z-contrast scanning transmission microscopy (STEM), and electron energy loss spectroscopy (EELS).The La0.67Ca0.33MnO3 (LCMO) samples were grown on (001) LaA1O3 (LAO) using pulsed laser deposition. X-ray diffraction indicated the films to be oriented with the [001] directions parallel to the <001> directions of the pseudo-cubic perovskite LAO. Rocking curve measurements using the (002) reflection from the film indicated a full width half maximum of less than 0.3°. A Philips EM-400 electron microscope at 100 kV and a VG HB603 STEM at 300 kV were employed for sample analysis.

Atomic Scale Analysis of Oxygen Vacancy Segregation At Grain Boundaries in Ceramic Oxides

2001 ◽  
Vol 7 (S2) ◽  
pp. 308-309
Author(s):  
N. D. Browning ◽  
J. P. Buban ◽  
Y. Ito ◽  
R. F. Klie ◽  
Y. Lei
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Ceramic Oxides ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Resolution Analysis ◽  
Z Contrast

The properties of ceramic oxides being developed for such varied applications as fuel cells, ionic transporting membranes, high-Tc superconductors, ferroelectrics and varistors are dominated by the presence of grain boundaries. Key to controlling the electronic properties of the grain boundaries in these materials is a fundamental understanding of the complex relationship between structure, composition and local electronic structure. The ability to characterize and directly correlate these parameters on the atomic scale is afforded by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Furthermore, the recent development of in-situ heating capabilities in the JEOL 201 OF STEM/TEM permits atomic resolution analysis to be performed at elevated temperatures and the interactions of grain boundaries with the oxygen vacancies determined.Figure 1 shows an example of the type of experiment that can be performed using these methods.

scholarly journals Direct Observation of Threading Dislocations in Gan by High Resolution z-contrast imaging

1998 ◽  
Vol 4 (S2) ◽  
pp. 660-661
Author(s):  
Y. Xin ◽  
N.D. Browning ◽  
S.J. Pennycook ◽  
P.D. Nellist ◽  
S. Sivananthan ◽  
...  
Keyword(s):  
High Resolution ◽  
Film Growth ◽  
Scanning Transmission Electron Microscope ◽  
Contrast Imaging ◽  
Light Emitting ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Short Wavelength Light ◽  
Film Substrate ◽  
Z Contrast

Wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers. One interesting issue concerning GaN is that the material is relatively insensitive to the presence of a density of dislocations which is six orders of magnitude higher than that for III-V arsenide and phosphide based LEDs. Although it is well known that these dislocations originate at the film-substrate interface during film growth, thread through the whole epilayer with line direction along <0001> and are perfect dislocations with Burgers vectors of a, c, or c+a, the reason why they have such a small effect on the properties of GaN is unclear.To develop a fundamental understanding of the properties of these dislocations, the core structures are studied here by high resolution Z-contrast imaging in a 300kV VG HB603 scanning transmission electron microscope (STEM) with a resolution of 0.13nm.

scholarly journals Z-Contrast Scanning Transmission Electron Microscopy Of Nanometer-Scale Coated Particulate Materials

1998 ◽  
Vol 4 (S2) ◽  
pp. 756-757
Author(s):  
H.J. Gao ◽  
Y. Yan ◽  
J. Fitz-Gerald ◽  
D. Kumar ◽  
R.K. Singh ◽  
...  
Keyword(s):  
Deep Understanding ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Particulate Materials ◽  
Atomic Structures ◽  
Scanning Transmission Electron ◽  
Novel Structure ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Z Contrast

Particulate materials with unique functional properties have been the focus of much attention in recent years. Of particular interest, due to their considerable scientific and technological importance, are particles coated with nanoparticles. These have greatly stimulated interest for their novel structure and properties. In these kinds of particulate materials, the interface structures between the support particle and the nanoparticle play a crucial role in controlling their properties. Consequently, imaging of the atomic structures at the interfaces can provide deep understanding of the relationship between the particulate and the corresponding properties. Z-contrast scanning transmission electron microscope (STEM) provides a new view of materials on the atomic scale, a direct image of atomic structure composition which can be interpreted without the need for any preconceived model structure. Therefore it is a powerful tool in the study of particulate materials. In this report, we will present the structures of 18 micron diameter alumina particles coated with Ag nanoparticles.

Electron Microscopy Studies of The Chemistry And Microstructure of BaF2 / YBa2Cu3O7-x Thin Films

1994 ◽  
Vol 52 ◽  
pp. 796-797
Author(s):  
J. L. Lee ◽  
C. A. Weiss ◽  
R. A. Buhrman ◽  
J. Silcox
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Thin Films ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Island Growth ◽  
Multilayer Systems ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Mgo Substrate

BaF2 thin films are being investigated as candidates for use in YBa2Cu3O7-x (YBCO) / BaF2 thin film multilayer systems, given the favorable dielectric properties of BaF2. In this study, the microstructural and chemical compatibility of BaF2 thin films with YBCO thin films is examined using transmission electron microscopy and microanalysis. The specimen was prepared by using laser ablation to first deposit an approximately 2500 Å thick (0 0 1) YBCO thin film onto a (0 0 1) MgO substrate. An approximately 7500 Å thick (0 0 1) BaF2 thin film was subsequendy thermally evaporated onto the YBCO film.Images from a VG HB501A UHV scanning transmission electron microscope (STEM) operating at 100 kV show that the thickness of the BaF2 film is rather uniform, with the BaF2/YBCO interface being quite flat. Relatively few intrinsic defects, such as hillocks and depressions, were evident in the BaF2 film. Moreover, the hillocks and depressions appear to be faceted along {111} planes, suggesting that the surface is smooth and well-ordered on an atomic scale and that an island growth mechanism is involved in the evolution of the BaF2 film.

scholarly journals Meso-Scale Transmission Electron Microscope Tomography Applied for Wax Distribution in Toner Particles

2013 ◽  
Vol 19 (S5) ◽  
pp. 58-61 ◽  
Author(s):  
Mino Yang ◽  
Jun-Ho Lee ◽  
Hee-Goo Kim ◽  
Euna Kim ◽  
Young-Nam Kwon ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Three Dimensional ◽  
Chromatic Aberration ◽  
Laser Printer ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Z Contrast ◽  
Contrast Image

AbstractDistribution of wax in laser printer toner was observed using an ultra-high-voltage (UHV) and a medium-voltage transmission electron microscope (TEM). As the radius of the wax spans a hundred to greater than a thousand nanometers, its three-dimensional recognition via TEM requires large depth of focus (DOF) for a volumetric specimen. A tomogram with a series of the captured images would allow the determination of their spatial distribution. In this study, bright-field (BF) images acquired with UHV-TEM at a high tilt angle prevented the construction of the tomogram. Conversely, the Z-contrast images acquired by the medium-voltage TEM produced a successful tomogram. The spatial resolution for both is discussed, illustrating that the image degradation was primarily caused by beam divergence of the Z-contrast image and the combination of DOF and chromatic aberration of the BF image from the UHV-TEM.

Towards 3D image-based nanocrystallography by means of transmission electron goniometry

2004 ◽  
Vol 839 ◽  
Author(s):  
Peter Moeck ◽  
Wentao Qin ◽  
Philip B. Fraundorf
Keyword(s):  
Lattice Structure ◽  
Three Dimensions ◽  
Structural Defects ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Z Contrast ◽  
Individual Nanoparticles ◽  
Nanocrystal Model ◽  
The Ideal

ABSTRACTIt is well known that the crystallographic phase and morphology of many materials changes with the crystal size in the tens of nanometer range and that many nanocrystals possess structural defects in excess of their equilibrium levels. A need to determine the ideal and real structure of individual nanoparticles, therefore, arises. High-resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM (STEM) when combined with transmission electron goniometry offer the opportunity of develop dedicated methods for the crystallographic characterization of nanoparticles in three dimensions. This paper describes tilt strategies for taking data from individual nanocrystals “as found”, so as to provide information on their lattice structure and orientation, as well as on the structure and orientation of their surfaces and structural defects. Internet based java applets that facilitate the application of this technique for cubic crystals with calibrated tilt-rotation and double-tilt holders are mentioned briefly. The enhanced viability of image-based nanocrystallography in future aberration-corrected TEMs and STEMs is illustrated on a nanocrystal model system.

scholarly journals Chemical Quantification of Atomic-Scale EDS Maps under Thin Specimen Conditions

2014 ◽  
Vol 20 (6) ◽  
pp. 1782-1790 ◽  
Author(s):  
Ping Lu ◽  
Eric Romero ◽  
Shinbuhm Lee ◽  
Judith L. MacManus-Driscoll ◽  
Quanxi Jia
Keyword(s):  
Atomic Scale ◽  
Specimen Thickness ◽  
Peak Width ◽  
Thin Specimen ◽  
Gaussian Peak ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Relationship ◽  
Chemical Quantification

AbstractWe report our effort to quantify atomic-scale chemical maps obtained by collecting energy-dispersive X-ray spectra (EDS) using scanning transmission electron microscopy (STEM) (STEM-EDS). With thin specimen conditions and localized EDS scattering potential, the X-ray counts from atomic columns can be properly counted by fitting Gaussian peaks at the atomic columns, and can then be used for site-by-site chemical quantification. The effects of specimen thickness and X-ray energy on the Gaussian peak width are investigated using SrTiO3 (STO) as a model specimen. The relationship between the peak width and spatial resolution of an EDS map is also studied. Furthermore, the method developed by this work is applied to study cation occupancy in a Sm-doped STO thin film and antiphase boundaries (APBs) present within the STO film. We find that Sm atoms occupy both Sr and Ti sites but preferably the Sr sites, and Sm atoms are relatively depleted at the APBs likely owing to the effect of strain.

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