The article explores the challenges in achieving sharp interfaces between polar and non-polar materials, particularly in multivalent oxides. The authors use atomic-scale electron energy loss spectroscopy to investigate the fundamental asymmetry between ionically and electronically compensated interfaces, both in terms of interfacial sharpness and carrier density. They find that for interfaces with mobile electrons, atomic disordering and stoichiometry changes are not necessary to achieve sharp interfaces. The study focuses on the (001) interfaces between SrTiO₃ and LaAlO₃, where the interface dipoles and band offsets introduce significant energy costs for atomically abrupt heterointerfaces. The authors propose a strategy to design sharp interfaces by removing interfacial screening charges and controlling the band offset, which can significantly improve the performance of oxide devices. Experimental results show that the "n-type" interface (AlO₂/LaO/TiO₂) has a higher roughness and free carriers, while the "p-type" interface (AlO₂/SrO/TiO₂) is compensated by oxygen vacancies, leading to a more insulating behavior. The study suggests that tuning the oxygen vacancy concentration can adjust the band offset, potentially enhancing the performance of oxide devices.The article explores the challenges in achieving sharp interfaces between polar and non-polar materials, particularly in multivalent oxides. The authors use atomic-scale electron energy loss spectroscopy to investigate the fundamental asymmetry between ionically and electronically compensated interfaces, both in terms of interfacial sharpness and carrier density. They find that for interfaces with mobile electrons, atomic disordering and stoichiometry changes are not necessary to achieve sharp interfaces. The study focuses on the (001) interfaces between SrTiO₃ and LaAlO₃, where the interface dipoles and band offsets introduce significant energy costs for atomically abrupt heterointerfaces. The authors propose a strategy to design sharp interfaces by removing interfacial screening charges and controlling the band offset, which can significantly improve the performance of oxide devices. Experimental results show that the "n-type" interface (AlO₂/LaO/TiO₂) has a higher roughness and free carriers, while the "p-type" interface (AlO₂/SrO/TiO₂) is compensated by oxygen vacancies, leading to a more insulating behavior. The study suggests that tuning the oxygen vacancy concentration can adjust the band offset, potentially enhancing the performance of oxide devices.