Sketched Oxide Single-Electron Transistor*

Devices that confine and process single electrons represent an important scaling limit of electronics. Such devices have been realized in a variety of materials and exhibit remarkable electronic, optical and spintronic properties. Here, we use an atomic force microscope tip to reversibly ``sketch'' single-electron transistors by controlling a metal-insulator transition at the interface of two oxides.\footnote{Cheng \textit{et al.}, Nature Nanotechnology \textbf{6}, 343 (2011).} In these devices, single electrons tunnel resonantly between source and drain electrodes through a conducting oxide island with a diameter of $\sim$1.5 nm. We demonstrate control over the number of electrons on the island using bottom- and side-gate electrodes, and observe hysteresis in electron occupation that is attributed to ferroelectricity within the oxide heterostructure. These single-electron devices may find use as ultradense non-volatile memories, nanoscale hybrid piezoelectric and charge sensors, as well as building blocks in quantum information processing and simulation platforms.