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Credit: Muqing Yu
PITTSBURGH--It has long been a dream to invent new materials from the "top down" choosing which atoms go where to engineer properties of interest. A technique created by researchers out of the Department of Physics and Astronomy enables them to "sketch" patterns of electrons into a programmable quantum material--lanthanum aluminate/strontium titanate or "LAO/STO". Using this approach, they can create quantum devices and with feature sizes comparable to the spacing between electrons, and even "sketch" artificial lattices for electrons to traverse, with extremely high precision.
To develop this capability, the researchers repurposed an electron beam lithography instrument, which is ordinarily used to create nanostructures by exposing a resist that hardens into a mask, enabling layers of material to be subsequently added or removed. Instead of operating the instrument at its usual value of 20,000 Volts, the researchers dialed it down to only a few hundred volts, where the electrons could not penetrate the surface of their oxide material, and instead--without any resist--catalyze a surface reaction that renders the LAO surface positively charged, and the LAO/STO interface locally conductive. The electron beam is 10,000 times faster at writing compared with atomic-force microscope-based lithography, without losing spatial resolution or ability to be reprogrammed. In addition, the authors showed that this technique can program the LAO/STO interface when integrated with other 2D layers such as graphene.