Real-time characterization of nanostructures written at the LaAlO$_3$/SrTiO$_3$ interface

Nanostructures can be written on the LaAlO$_3$/SrTiO$_3$ interface using conductive AFM lithography\footnote{C. Cen, \textit{et al.}, \textit{Science} \textbf{323}, 1026 (2009)}. These structures can be configured into devices including photodetectors\footnote{P. Irvin, \textit{et al.}, \textit{Nat. Photonics} \textbf{4}, 849 (2010)} and transistors\footnote{G. Cheng, \textit{et al.}, \textit{Nat. Nanotechnol.} \textbf{6}, 343 (2011)}. Characterization of complex devices requires simultaneous measurements between several pairs of electrodes. We have developed a method to take measurements between all electrodes simultaneously by both measuring and applying a bias at a unique frequency to each electrode. Fourier analysis is then used to separate measured signals by source terminal. This allows us to efficiently characterize multi-terminal devices in real-time, as they are being created. This method will allow for the use of new experimental techniques.