Transparent Superconductor on the Base of In_2- <i> _y </i>Sn<i> _y </i>O_3- <i> _δ </i>: Unraveling the Electrochemical Doping Mechanism

Photonic and superconducting platforms are at the core of modern quantum technologies. However, most existing superconductors are opaque and highly absorptive. Indium-tin oxide (ITO) films reduced by electrochemical intercalation provide a promising solution for tunable superconductivity and transparency in the visible, NIR, and mid-IR optical regions. Understanding the mechanism of electrochemical reaction at the ITO surface and the dimensionality of the emerging superconducting state is a crucial step in developing devices that utilize the interaction of electromagnetic waves with a quantum state. Here we studied three routes to tune the charge density in ITO films, that might lead to the emergence of the superconducting state: doping with heterovalent atoms; electrochemical intercalation; and synthesis of oxygen-deficient ITO films. While the first does not show superconductivity at any level of doping, the second induces two-dimensional superconductivity at the ITO surface, and the third route creates three-dimensional superconductivity in bulk.