Patterning of Superconducting Two‐Dimensional Electron Gases based on AlO_x/KTaO₃ (111) Interfaces

Abstract

The versatility of properties displayed by two‐dimensional electron gases (2DEGs) at oxide interfaces has fostered intense research in hope of achieving exotic electromagnetic effects in confined systems. Of particular interest is the recently discovered superconducting state appearing in (111)‐oriented KTaO3 interfaces, with a critical temperature Tc≈2 K, almost 10 times higher than that of SrTiO3‐based 2DEGs. Just as in SrTiO3‐based 2DEGs, fabricating devices in this new system is a technical challenge due to the fragility of the 2DEG and the propensity of bulk KTaO3 to become conducting outside the devices upon adventitious oxygen vacancy doping. Here, three different techniques are presented for patterning Hall bars in AlOx/KTaO3 (111) heterostructures. The devices show superconducting transitions ranging from 1.3 to 1.78 K, with limited degradation from the unpatterned thin film, and enable an efficient tuning of the carrier density by electric field effect. The array of techniques allows for the definition of channels with a large range of dimensions for the design of various kinds of devices to explore the properties of this system down to the nanoscale.