Off-axis electron holography and microstructure of Ba0.5Sr0.5TiO3 thin film grown on LaAlO3

Epitaxial Ba0.5Sr0.5TiO3 thin films grown on the (001) LaAlO3 substrates with the ferroelectric transition of about 250K have been investigated by TEM and off-axis electron holography. Cross-sectional TEM observations show that the 350nm-thick Ba0.5Sr0.5TiO3 film has a sharp interface with notable misfit dislocations. Off-axis electron holographic measurements reveal that, at low temperatures, the ferroelectric polarization results in systematic accumulations of negative charges on the interface and positive charges on the film surface, and, at room temperature, certain charges could only accumulate at the interfacial dislocations and other defective areas.