The small probe size and high spatial resolution of TEM offer unique capabilities for studying interfaces of materials. Compared with neutron and x-ray diffraction, TEM is often considered nonquantitative. In HREM, especially, atomic images can alter significantly with imaging parameters that are often difficult to determine experimentally. The weakness of the HREM can be circumvented by a multiprobe approach, i.e., the combined use of a wide range of TEM techniques, such as B-F/D-F imaging, nano-probe EDS and EELS, electron diffraction, and strain-field characterization. Quantitative analysis, based on the calculations and experimental TEM data, is often necessary to correctly derive the crystal-, chemical-, and electronic-structure of an interface.

We review our multiprobe approach in studying interfaces in complex systems of superconductors, starting with the simplest interface, twin boundary, in YBa2Cu3O7-δ. Although HREM suggested that there are two types of twin boundaries, with and without a ˜d110 lattice translation at the boundaries, the structural characteristics of the interfaces were determined by analyses of the interfacial δ-α fringe and the associated diffuse scattering, while EELS revealed their association with the local oxygen/hole concentration.