Interface

Nanoscale control of the quasi-two-dimensional electron gas at the LaAlO₃/SrTiO₃(LAO/STO)
interface by a conductive probe tip has triggered the development of a number of novel
electronic devices. While the spatial distribution of the conductance is crucial for such devices, it
is challenging to directly visualize the local electrical properties at the buried interface. Here we
demonstrate conductivity imaging of sketched nanostructures at the LAO/STO interface by
microwave impedance microscopy (MIM) with a lateral resolution on the order of 100 nm. The
sheet conductance extracted from the MIM data agrees with the transport measurement. The tip-
induced insulator-to-metal transition is observed above a threshold voltage of +4 V. Our work
paves the way to study emergent phenomena at oxide interfaces by probing nanoscale
conductance distribution.