The measurement and interpretation of electrostatic potential profiles across grain boundaries in strontium titanate

Results from a systematic Fresnel contrast (in-line electron holography) study of a large number of grain boundary potentials from undoped, donor-doped and acceptor-doped polycrystalline strontium titanate samples are summarised. An assessment is made of whether the measured variations in potential can be used to provide information about space charge distributions at the boundaries, or whether they are instead dominated by local changes in composition, density and specimen thickness. The effects on the measured contrast of both specimen preparation for transmission electron microscopy and irradiation by the high-energy electron beam are also discussed.