IMF2017

There is a growing interest for structural and electric properties of ferroelectric and ferroelastic domain walls. The emerging field of domain boundary engineering holds the promise of using the distinct functional properties of domain walls in and as devices. Here, we report a study of ferroelastic domain walls in paraelectric, non-polar CaTiO₃. We report the observation of a strong signal in piezoelectric resonance spectroscopy (RPS), which we argue is due to the polar character of the walls. We also use a low energy electron microscope (LEEM) to observe twin walls in CaTiO₃. As expected, adjacent domains present the same surface potential because the material is non-polar. However, the twin walls show clear surface potential contrast with respect to the domains. The same contrast is observed on a work function map. This provides direct in-situ evidence of the polar nature of ferroelastic twin walls in CaTiO₃. In a second step, we study the manipulation of the surface charge at twin walls upon electron injection, realized by increasing the energy of the incoming electron beam of the LEEM. We show that the contrast between domain and domain walls vanishes upon electron irradiation with a characteristic time of 10 - 15 minutes. It is possible to recover the initial state, i.e. before charge injection, by annealing above 250 °C. The ability to observe polarity at the nanoscale and to tune the surface charge at twin walls gives perspectives toward functionalization of polar twin walls in CaTiO₃.