Side gate tuning of electron transport in SrTiO₃ hall bar devices

Strontium Titanate (SrTiO₃) is an interesting platform for studying electron transport in gated devices and nanostructures as it hosts a unique set of properties such as gate-tunable superconductivity, spin-orbit coupling, and incipient ferroelectricity. In this work, we study electrostatic side gate tuning of two-dimensional electron gas (2DEG) at SrTiO₃ surfaces. We patterned hall bar devices on SrTiO₃ via electron beam lithography and measured them across temperatures from 10mK to room temperature, using a dilution refrigerator and a pulse tube cryocooler. The device channels were exposed to hydrogen plasma which creates a 2DEG near the surface of SrTiO₃. We measured a 2DEG Hall density of 1.7 x 10¹⁴ cm⁻² and Hall mobility up to 5500 cm²/Vs. Lateral side gates, positioned at 20 µm and 60 µm from the channels, allow for electrostatic tuning of the 2DEG channel. While gate capacitance is expected to scale inversely with gate-to-channel distance from simple comparisons to a parallel plate capacitor, our results showed a much more gradual scaling effect.