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Elemental doping at coherent interfaces is very difficult and rarely used to improve the interfacial properties since coherent interfaces have low interfacial energies and lack open space for trapping dopant atoms. Exploring universally applicable strategies for elemental doping at coherent interfaces represents an important progress in interface science and engineering. In this study, Nb atoms are successfully doped at coherent (001) LaAlO 3 /anatase-TiO 2 interfaces, which enhances greatly the efficiency of photocatalytic hydrogen production from water. Transmission electron microscopy investigations reveal that both LaO- terminated and AlO 2 -terminated LaAlO 3 /anatase-TiO 2 interfaces can trap two layers of Nb atoms, which accompanies with the formation of La vacancies between them. First-principles calculations suggest that Nb atoms segregate at the interfaces under the action of potential gradient, which increases significantly the strength of the built-in electric field in TiO 2 , thereby facilitating the separation of photogenerated carriers and improving the photocatalytic performance. The H 2 production of the Nb doped coherent interface is about 4 times that of the pristine coherent interface. Since potential gradient widely exists at various interfaces including the coherent ones, elemental doping by potential gradient should be an universally applicable fabrication method for tuning the properties of interfaces and heterostructures. [Display omitted] [ABSTRACT FROM AUTHOR]

Domain walls affect significantly ferroelectric and magnetic properties of magnetoelectric multiferroics. The stereotype is that the ferroelectric polarization will reduce at the domain walls due to the incomplete shielding of depolarization field or the effects of gradient energy. By combining transmission electron microscopy and first-principles calculations, we demonstrate that the ferroelectric polarization of tail-to-tail 180° domain walls in ε-Fe 2 O 3 is regulated by the bound charge density. A huge enhancement (43%) of ferroelectric polarization is observed in the type I domain wall with a low bound charge density, while the ferroelectric polarization is reduced to almost zero at the type II domain wall with a high bound charge density. The magnetic coupling across the type I and type II ferroelectric domain walls are antiferromagnetic and ferromagnetic, respectively. Revealing mechanisms for enhancing ferroelectric polarization and magnetic behaviors at ferroelectric domain walls may promote the fundamental research and potential applications of magnetoelectric multiferroics., (© 2024. The Author(s).)