These authors contributed equally to this work.The ability to control materials properties through interface engineering is demonstrated by the appearance of conductivity at the interface of certain insulators, most famously the {001} interface of the band insulators LaAlO 3 (LAO) and TiO 2 -terminated SrTiO 3 (STO) 1,2 . Transport and other measurements in this system display a plethora of diverse physical phenomena 3-14 . To better understand the interface conductivity, we used scanning superconducting quantum interference device (SQUID) microscopy to image the magnetic field locally generated by current in an interface. At low temperature, we found that the current flowed in highly conductive narrow paths oriented along the crystallographic axes, embedded in a less conductive background. The configuration of these paths changed upon thermal cycling above the STO cubic to tetragonal structural transition temperature, implying that local conductivity is strongly modified by STO tetragonal domain

The rich array of conventional and exotic electronic properties that can be generated by oxide heterostructures is of great potential value for device applications. However, only single transistors bare of any circuit functionality have been realized from complex oxides. Here, monolithically‐integrated n‐type metal‐oxide‐semiconductor logic circuits are reported that utilize the two‐dimensional electron liquid generated at the LaAlO3/SrTiO3 interface. Providing the capability to process the signals of functional oxide devices such as sensors directly on oxide chips, these results illustrate the practicability and the potential of oxide electronics.

Solid-state heterostructures are the cornerstone of modern electronics. To enhance the functionality and performance of integrated circuits, the spectrum of materials used in the heterostructures is being expanded by an increasing number of compounds and elements of the periodic table. While the integration of liquids and solid-liquid interfaces into such systems would allow unique and advanced functional properties and would enable integrated nanoionic circuits, solid-state heterostructures that incorporate liquids have not been considered thus far. Here solid-state heterostructures with integrated liquids are proposed, realized, and characterized, thereby opening a vast, new phase space of materials and interfaces for integrated circuits. Devices containing tens of microscopic capacitors and field-effect transistors are fabricated by using integrated patterned NaCl aqueous solutions. This work paves the way to integrated electronic circuits that include highly integrated liquids, thus yielding a wide array of novel research and application opportunities based on microscopic solid/liquid systems.

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The cover displays an optical microscopy image (interference contrast) of a monolithically integrated all‐oxide NMOS chip, showing sections of five ring‐oscillators. The field effect transistors of these integrated circuits are based on the conducting, twodimensional electron liquid formed at LaAlO3/SrTiO3 interfaces. This work, reported in article 1300031 by R. Jany and co‐workers, represents a breakthrough in oxide electronics. Providing the capability to actively process the signals of oxide devices such as sensors on‐chip, these results illustrate the practicability and the potential of electronics based on functional oxides