Z-contrast imaging of an ordered interface structure in the Si/CoSi2/Si system

1993 ◽  
Vol 51 ◽  
pp. 802-803
Author(s):  
M. F. Chisholm ◽  
D. E. Jesson ◽  
S. J. Pennycook ◽  
S. Mantl
Keyword(s):  
Atomic Structure ◽  
Substrate Surface ◽  
Interface Structure ◽  
Unit Cell ◽  
Contrast Imaging ◽  
Treatment Results ◽  
Semiconductor Interfaces ◽  
Contrast Technique ◽  
Z Contrast ◽  
Insight Into

We show the atomic structure of buried CoSi2/Si(001) boundaries involves a 2×1 ordering of the interfacial Co atoms. The ability to directly image and interpret this unforeseen structure is possible through the Z-contrast technique, and presents a new level of insight into the important and controversial relationship between the atomic structure and electronic properties, such as the energy barrier for electron transport across metal-semiconductor interfaces.The buried CoSi2 layer was produced by implanting Co+ ions (200 keV, 2 × 1017 ions/cm2) in a Si(001) substrate heated to 350°C. The substrate was capped with 200 nm of SiO2 and then given a two-step anneal in high purity argon (750°C for 30 s + 1150°C for 10 s). This treatment results in a continuous buried CoSi2 layer ~70 nm thick, ~90 nm below the substrate surface. The layer and the substrate are oriented such that the cubic CaF2 unit cell of CoSi2 is aligned parallel to the cubic unit cell of Si.

A Combined-Techniques Approach to Elucidating Crystalline Interface Atomic Structure

1996 ◽  
Vol 466 ◽  
Author(s):  
E. C. Dickey ◽  
V. P. Dra Vid ◽  
S. J. Pennycook ◽  
P. D. Nellist ◽  
D. J. Wallis
Keyword(s):  
Atomic Structure ◽  
Three Dimensional ◽  
Interface Structure ◽  
Contrast Imaging ◽  
Imaging And Spectroscopy ◽  
Complementary Techniques ◽  
Electron Imaging ◽  
Z Contrast ◽  
Interface Structures

ABSTRACTA case study is presented in which HREM, Z-Contrast Imaging and EELS are used as complementary techniques for elucidating interface structure. The NiO-ZrO2(cubic) interface is investigated along two orthogonal directions by these electron imaging and spectroscopy techniques to reveal the three-dimensional interface structure. Based on findings from this study, a protocol is suggested for using all three experimental techniques to gain a thorough understanding of interface structures.

Atomic structure determination of NIO-ZRO2(CaO) and NI-ZRO2(CaO) interfaces using Z-contrast imaging and EELS

1996 ◽  
Vol 54 ◽  
pp. 106-107
Author(s):  
E.C. Dickey ◽  
V.P. Dravid ◽  
P. Nellist ◽  
D.J. Wallis ◽  
N. D. Browning ◽  
...  
Keyword(s):  
Atomic Structure ◽  
Bulk Material ◽  
Interface Structure ◽  
Structure Property ◽  
Contrast Imaging ◽  
Spatially Resolved ◽  
Structure Property Relationships ◽  
Powerful Approach ◽  
Resolution Imaging ◽  
Z Contrast

Combining atomic-resolution imaging with spatially resolved electron energy loss spectroscopy (EELS) is a powerful approach to probing the geometric, chemical and electronic aspects of internal interfaces. By elucidating these interrelated constituents of interface structure, one can begin to understand the influence of the interface atomic structure on relevant bulk material properties, deducing atomic structure/property relationships. The combined Z-contrast and EELS approach was applied to two types of heterophase interfaces: oxide-oxide (NiO-ZrO2) and metal-oxide (Ni-ZrO2). The interface structure will be discussed in light of these experiments and compared to previous HREM results.

High-resolution z-contrast imaging of semiconductor interfaces

1989 ◽  
Vol 47 ◽  
pp. 468-469
Author(s):  
S. J. Pennycook
Keyword(s):  
High Resolution ◽  
Phase Contrast ◽  
Contrast Imaging ◽  
Compositional Modulation ◽  
Semiconductor Interfaces ◽  
Complex Figure ◽  
Thin Region ◽  
Stem Image ◽  
Annular Detector ◽  
Z Contrast

Using a high-angle annular detector on a high-resolution STEM it is possible to form incoherent images of a crystal lattice characterized by strong atomic number or Z contrast. Figure 1 shows an epitaxial Ge film on Si(100) grown by oxidation of Ge-implanted Si. The image was obtained using a VG Microscopes' HB501 STEM equipped with an ultrahigh resolution polepiece (Cs ∽1.2 mm, demonstrated probe FWHM intensity ∽0.22 nm). In both crystals the lattice is resolved but that of Ge shows much brighter allowing the interface to be located exactly and interface steps to be resolved (arrowed). The interface was indistinguishable in the phase-contrast STEM image from the same region, and even at higher resolution the location of the interface is complex. Figure 2 shows a thin region of an MBE-grown ultrathin super-lattice (Si8Ge2)100. The expected compositional modulation would show as one bright row of dots from the 2 Ge monolayers separated by 4 rows of lighter Si columns. The image shows clearly that strain-induced interdiffusion has occurred on the monolayer scale.

Atomic Structure and Property Correlation in Pulsed Laser Deposited High -Tc Films

1998 ◽  
Vol 526 ◽  
Author(s):  
R. Kalyanaraman ◽  
S. Oktyabrsky ◽  
K. Jagannadham ◽  
J. Narayan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Substrate Surface ◽  
Pulsed Laser ◽  
Structure And Property ◽  
Transmission Electron ◽  
Tilt Boundaries ◽  
Z Contrast

AbstractThe atomic structure of grain boundaries in pulsed laser deposited YBCO/MgO thin films have been studied using transmission electron microscopy. The films have perfect texturing with YBCO(001)//MgO(001), giving rise to low-angle [001] tilt boundaries from the grains with the c-axis normal to substrate surface. Low angle grain boundaries have been found to be aligned preferentially along (100) and (110) interface planes. The energy of (110) boundary planes described by an alternating array of [100] and [010] dislocation is found to be comparable to the energy of a (100) boundary. The existence of these split dislocations is shown to further reduce the theoretical current densities of these boundaries indicating that (110) boundaries carry less current as compared to (100) boundaries of the same misorientation angle. Further, Z-contrast transmission electron microscopy of a 42° asymmetric high-angle grain boundary of YBCO shows evidence for the existence of boundary fragments and a reduced atomic density along the boundary plane

Simulation and Quantification of High-Resolution Z-Contrast Imaging of Semiconductor Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
D. E. Jesson ◽  
S. J. Pennycook ◽  
M. F. Chisholm
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Image Interpretation ◽  
Bloch Wave ◽  
Small Computer ◽  
High Angle ◽  
Contrast Imaging ◽  
Resolution Function ◽  
Semiconductor Interfaces ◽  
Z Contrast

ABSTRACTIncoherent characteristics of Z-contrast STEM images are explained using a Bloch wave approach. To a good approximation, the image is given by the columnar high-angle cross-section multiplied by the s-state intensity at the projected atom sites, convoluted with an appropriate resolution function. Consequently, image interpretation can be performed intuitively and quantitative simulation can be implemented on a small computer. The feasibility of ‘column-by-column’ compositional mapping is discussed.

scholarly journals Atomic Scale Structure and Chemistry of Interfaces by Z-Contrast Imaging and Electron Energy Loss Spectroscopy in the Stem

1994 ◽  
Vol 341 ◽  
Author(s):  
M. M. McGibbon ◽  
N. D. Browning ◽  
M. F. Chisholm ◽  
A. J. McGibbon ◽  
S. J. Pennycook ◽  
...  
Keyword(s):  
High Resolution ◽  
Energy Loss ◽  
Electron Energy ◽  
Atomic Structure ◽  
Electron Energy Loss Spectroscopy ◽  
Atomic Scale ◽  
Chemical Information ◽  
Contrast Imaging ◽  
Z Contrast ◽  
Electron Energy Loss

AbstractThe macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted directly without the need for preconceived atomic structure models (1). Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale (2). The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface (3). In this paper we use the complimentary techniques of high resolution Zcontrast imaging and PEELS to investigate the atomic structure and chemistry of a 25° symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.

Atomic resolution determination of the structure and chemistry of ceramic grain boundaries

1995 ◽  
Vol 53 ◽  
pp. 320-321
Author(s):  
N. D. Browning ◽  
M. M. McGibbon ◽  
M. F. Chisholm ◽  
S. J. Pennycook
Keyword(s):  
Grain Boundaries ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Secondary Phases ◽  
Contrast Imaging ◽  
Scanning Transmission ◽  
Recent Developments ◽  
Contrast Technique ◽  
Z Contrast

Characterization of grain boundaries in ceramics is complicated by the multicomponent nature of the materials, the presence of secondary phases, and the tendency for the grain boundary plane to “wander” on the length scale of a few nanometers. However, recent developments in the scanning transmission electron microscope (STEM) have now made it possible to correlate directly the structure, composition and bonding at grain boundaries on the atomic scale. This direct experimental characterization of grain boundaries is achieved through the combination of Z-contrast imaging (structure) and electron energy loss spectroscopy (EELS) (composition and bonding). For crystalline materials in zone-axis orientations, where the atomic spacing is larger than the probe size, the Z-contrast technique provides a direct image of the metal (high Z) columns. This image, being formed from only the high-angle scattering, can be used to position the electron probe with atomic precision for simultaneous EELS. Under certain collection conditions, the spectrum can have the same atomic spatial resolution as the image, thus permitting the spectra to be correlated with a known atomic location.

Ab initio determination of atomic structure of Zn–Zr precipitates in a Mg–Nd–Zn–Zr alloy

2019 ◽  
Vol 75 (4) ◽  
pp. 564-569 ◽  
Author(s):  
W. Z. Wang ◽  
X. Z. Zhou ◽  
Z. Q. Yang ◽  
Y. Qi ◽  
H. Q. Ye
Keyword(s):  
Electron Diffraction ◽  
Ab Initio ◽  
Atomic Structure ◽  
Unit Cell ◽  
Atomic Resolution ◽  
Contrast Imaging ◽  
Beam Electron ◽  
Tilt Series ◽  
Zr Alloy

The atomic structure of nanometre-sized Zn–Zr precipitates in a Mg alloy is determined by combining tilt series of micro-beam electron diffraction with atomic resolution Z-contrast imaging. The stoichiometry of the Zn–Zr precipitates is Zn2Zr3 with a primitive tetragonal structure (space group P42/mnm, a = b = 0.761 nm, c = 0.682 nm). There are 20 atoms in the unit cell of tetragonal Zn2Zr3, comprising 12 Zr atoms at the 4d, 4f, 4g positions and eight Zn atoms at the 8j positions.

Atomic Structure of Si-SiO2 Interface

1997 ◽  
Vol 3 (S2) ◽  
pp. 459-460
Author(s):  
G. Duscher ◽  
F. Banhart ◽  
H. Müllejans ◽  
S.J. Pennycook ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Structure ◽  
Phase Contrast ◽  
Thermally Grown Oxide ◽  
Interface Roughness ◽  
Spatial Difference ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Z Contrast

Investigations of the atomic structure of Si-SiO2 interfaces have mostly been performed with high resolution transmission electron microscopy. However, the interpretation of the phase contrast in the amorphous phase at the interface is not unique. While Ourmazd et al. concluded on a crystalline phase at the Si-SiO2 interface, Akatsu and Ohdomari attributed the same contrast to an interface roughness parallel to the incident electrons.We investigated the Si-SiO2 interface by studying the ELNES of the O-K edge with the spatial difference technique with a dedicated STEM with l00kV (VG HB501 UX). Also the interface was studied by Z-contrast imaging with a 300 kV dedicated STEM (VG HB603 U). Silicon wafers (110) were first thermally oxidised to produce a SiO2 layer. The thermally grown oxide was used as a substrate for liquid phase epitaxy of silicon, given two {111} Si-SiO2 interfaces in the sample grown by two different techniques (see fig. 1).

Z-Contrast Imaging of Grain-Boundary Core Structures in Semiconductors

MRS Bulletin ◽  
1997 ◽  
Vol 22 (8) ◽  
pp. 53-57 ◽  
Author(s):  
M.F. Chisholm ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Phase Contrast ◽  
Atomic Scale ◽  
Resolving Power ◽  
Boundary Structure ◽  
Contrast Imaging ◽  
Contrast Technique ◽  
Z Contrast

Interest in semiconductor grain boundaries relates to the development of polycrystalline materials for photovoltaics and integrated-circuit interconnects. Although these structures are responsible for deleterious electrical effects, there are few experimental techniques available to study them at the required atomic scale. Therefore models of the physical processes occurring at grain boundaries have necessarily taken a macroscopic approach. Fortunately recent developments have resulted in tools that provide unprecedented glimpses into these interfaces and that will allow us to address anew the connection between grain-boundary structure and properties.Z-Contrast ImagingWhen exploring the unknown, we rely heavily on our eyes (incoherent imaging) to provide a direct image of a new object. In order to explore the unforeseen atomic configurations present at extended defects in materials, it again would be desirable if one could obtain a directly interpretable image of the unfamiliar structures present in the defect cores. Z-contrast electron microscopy provides such a view with both atomic resolution and compositional sensitivity.This high-resolution imaging technique differs from conventional high-resolution phase-contrast imaging. The phase-contrast technique produces a coherent image, an interference pattern formed by recombining the waves diffracted by the specimen. In the Z-contrast technique, the image is incoherent; it is essentially a map of the scattering power of the specimen. Additionally as was first determined by Lord Rayleigh, the incoherent mode of image formation has double the resolving power of the coherent mode.

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