High-resolution electron microscopy of metal/metal and metal/metal-oxide interfaces in the Ag/Ni and Au/Ni systems
- PDF / 1,865,952 Bytes
- 9 Pages / 593.28 x 841.68 pts Page_size
- 88 Downloads / 243 Views
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 (lll)Ag or (lll)Au interplanar spacings from the interfaces. I. INTRODUCTION
Heterophase interfaces between two similar or dissimilar materials play an important role and often perform controlling functions in systems of practical interest, such as electronic packaging,1 thin film technology,2 composites, and in ceramic/metal or in ceramic/ ceramic joining.3-4 Interfaces are also important in internal and external oxidation processes of metallic alloys. The bonding and adhesion at metal/metal-oxide interfaces can dominate many important properties of these materials.5 A number of observations of heterophase interfaces by high-resolution electron microscopy (HREM) have been reported in the last few years. The majority of atomic-level observations were obtained on semiconductor materials. HREM has made significant contributions to the understanding of the structures of silicon-silicide interfaces and semiconductor-metal interfaces.6 Recently several metal/ceramic interfaces have also been studied, for example Nb/Al 2 O 3 , 7 Pt/NiO, and Cu/NiO.8 Similarly, interfaces between precipitates and the matrix have been observed in a variety of systems. For instance, metal/metal-oxide interfaces generated by the internal oxidation of alloys have been characterized for Ag-Cd,910 Pd-Ni,10 Nb-Al,11 and Al-Cu-Li.12 Most of these HREM observations have been treated qualitatively, in the sense that certain structural features are directly interpreted from images near optimum defocus. Considerable insights into the overall characteristics of an interface can be gained from such an approach. More advanced techniques include the deduction of interface structures, based on comparison of observed images with image simulations of atomistic
interface models.9 Finally, atomistic computer simulations of interfaces can be combined with image simulations and HREM observations to allow a direct comparison between computer simulated and observed interface structures. In principle, one can deduce from HREM observations of interfaces a number of parameters of interest for the c
Data Loading...
