Mechanism for writing and erasing nanostructures at the LaAlO$_{3}$/SrTiO$_{3}$ interface using vacuum AFM

Nanoscale control of the metal-insulator transition in LaAlO$_{3} $/SrTiO$_{3}$ heterostructure can be achieved using local voltages applied by a conducting AFM probe. One proposed mechanism for the writing process (C.S. Hellberg, unpublished) involves adsorbed H$_{2}$O which dissociates into OH$^{-}$ and H$^{+}$ which are then selectively removed by a biased AFM probe. To test this mechanism, writing and erasing experiments are performed in a vacuum AFM ($2\times10^{-5}$ Torr) using various gas mixtures. We find that it is not possible to write nanostructures in vacuum or in the presence of several gas mixtures that do not contain H$_{2}$O.