Structural Relaxations At Metal / Metal Oxide Interfaces

MRS Proceedings ◽

10.1557/proc-238-763 ◽

1991 ◽

Vol 238 ◽

Cited By ~ 1

Author(s):

W. Mader

Keyword(s):

Metal Oxide ◽

Relative Strength ◽

Model Systems ◽

Misfit Dislocations ◽

Orientation Relationships ◽

Oxide Systems ◽

Oxide Interfaces ◽

Metal Metal ◽

High Resolution Tem ◽

Interacting Systems

ABSTRACTRecent work is reviewed on the structure of metal/metal oxide interfaces in model systems with well defined orientation relationships and boundary inclination. Structural relaxations established upon interface formation may be described as misfit dislocations which can be investigated using conventional and high resolution TEM. The conditions for obtaining informations at an atomistic scale using HRTEM are critically discussed. Specifically, geometrical restrictions are found to be critical in HRTEM study of {111} interfaces in fee metal -fee oxide systems. Different misfit dislocation networks at {100} interfaces in fee metal - fee oxide systems were observed which may be correlated to the relative strength of metal-anion and metal-cation bonds at the interface. In strongly interacting systems misfit dislocations can possess an equilibrium stand-off distance from the interface. In the system Nb-Al2O3 the interface is shown to be coherent by the registry of atomic columns adjacent to the interface. In this configuration energy is minimized by unbroken strong interfacial bonds and misfit localization in the elastically softer metal.

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High-resolution electron microscopy of metal/metal and metal/metal-oxide interfaces in the Ag/Ni and Au/Ni systems

Journal of Materials Research ◽

10.1557/jmr.1990.1995 ◽

1990 ◽

Vol 5 (9) ◽

pp. 1995-2003 ◽

Cited By ~ 42

Author(s):

Y. Gao ◽

Karl L. Merkle

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Metal Oxide ◽

High Resolution Electron Microscopy ◽

Misfit Dislocations ◽

Oxide Systems ◽

Lattice Statics ◽

Embedded Atom ◽

Resolution Electron ◽

Metal Metal

The atomic structures of heterophase interfaces with large misfits (>14% in Ag/Ni and Au/Ni) and with small misfits (∼2% in Ag/NiO and Au/NiO) have been studied by high-resolution electron microscopy (HREM). It is found that all interfaces are strongly faceted on (111) planes. This indicates that (111) interfaces have the lowest interfacial energy in both metal/metal and metal/metal-oxide systems. For the metal interfaces, this also agrees with determinations of interfacial energies by lattice statics calculations. The large misfit of Ag/Ni and Au/Ni interfaces is accommodated by misfit dislocations. Observations of misfit localization by HREM are in good agreement with images derived from computer simulation, based on relaxed structures, obtained in embedded atom calculations. All misfit dislocations at the Ag/Ni and Au/Ni interfaces lie exactly in the plane of the interfaces, while the dislocations at Ag/NiO and Au/NiO interfaces reside at a stand-off distance, 3 to 4 (111)Ag or (111)Au interplanar spacings from the interfaces.

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Quasiperiodic interfaces: HREM observations of grain and phase boundaries

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174795 ◽

1990 ◽

Vol 48 (4) ◽

pp. 332-333

Author(s):

K. L. Merkle

Keyword(s):

Atomic Structure ◽

Direct Determination ◽

Lattice Parameter ◽

Atomic Scale ◽

Misfit Dislocations ◽

Oxide Systems ◽

Atomic Structures ◽

Periodic Arrays ◽

Parameter Ratio ◽

Metal Metal

The atomic structures of internal interfaces have recently received considerable attention, not only because of their importance in determining many materials properties, but also because the atomic structure of many interfaces has become accessible to direct atomic-scale observation by modem HREM instruments. In this communication, several interface structures are examined by HREM in terms of their structural periodicities along the interface.It is well known that heterophase boundaries are generally formed by two low-index planes. Often, as is the case in many fcc metal/metal and metal/metal-oxide systems, low energy boundaries form in the cube-on-cube orientation on (111). Since the lattice parameter ratio between the two materials generally is not a rational number, such boundaries are incommensurate. Therefore, even though periodic arrays of misfit dislocations have been observed by TEM techniques for numerous heterophase systems, such interfaces are quasiperiodic on an atomic scale. Interfaces with misfit dislocations are semicoherent, where atomically well-matched regions alternate with regions of misfit. When the misfit is large, misfit localization is often difficult to detect, and direct determination of the atomic structure of the interface from HREM alone, may not be possible.

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