Distance from GB (nm)

Figure 42. (a) Electron hologram of a Mn-doped grain boundary in SrTiO3 acquired using a Hitachi HF-2000 FEG-TEM. The interference fringe spacing is 0.14 nm. (b) Phase profile measured across grain boundary shown in (a). (c) Charge density profile inferred by applying Poisson's equation direction to the phase profile shown in (b). The charge density profile suggests the presence of negative grain boundary charge and compensating positive space charge. The spatial extent of the boundary charge is approximately 1.4 nm. Reprinted with permission from [342], V. Ravikumar et al., J. Phys. D: Appl. Phys. 29, 1799 (1996). © 1996, Institute of Physics Publishing. (d) Electron hologram acquired from a Nb-doped grain boundary in SrTiO3 that has a current flowing across it in-situ in the TEM. (e) Measured phase shift across the boundary shown in (d), both before applying a current and as a current is applied. The absence of contrast at the boundary when a current is flowing suggests barrier breakdown. Reprinted with permission from [357], K. D. Johnson and V. P. Dravid, Appl. Phys. Lett. 74, 621 (1999). © 1999, American Institute of Physics.

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