Madison King1,Emma Batson2,Karl Berggren2,Stephanie Hurst1
Northern Arizona University1,Massachusetts Institute of Technology2
Madison King1,Emma Batson2,Karl Berggren2,Stephanie Hurst1
Northern Arizona University1,Massachusetts Institute of Technology2
The use of solid-state qubits in quantum technologies has created a need for efficient electro-optical transduction to avoid loss that comes with transmitting data at microwave frequencies over optical fibers in a quantum network [1]. Through the integration of superconducting electronics and quantum photonics, efficient transduction and read out of qubits can be achieved. The use of a transparent superconducting material is ideal to avoid efficiency loss in these circuits due to photon absorption. It has been demonstrated that indium tin oxide (ITO), a transparent semiconductor, behaves as a superconductor with a transition temperature (<i>T<sub>c</sub></i>) between 2 – 4 K when doped to a charge carrier concentration of 10<sup>21</sup> cm<sup>-3</sup> [2, 3]. This work is a part of collaborative effort to characterize the structure, composition, and electro-optical properties of superconducting ITO thin films prepared by two different methods. Our prior work has shown that commercially available ITO can be electrochemically reduced, permitting superconductivity. This process has been found to generate a rough nanoparticle layer on the surface of the ITO thin film [4].<br/>Here we present the characterization of ITO thin films with applications as a transparent superconductor prepared by a spin coating method. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) measurements provide details on surface and cross-section characteristics of the ITO thin films. The transparency of the thin films has been quantified through ellipsometry along with UV-visible spectroscopy and their <i>T<sub>c</sub></i> values determined.<br/>[1] Lambert, N. J.; Rueda, A.; Sedlmeir, F.; Schwefel, H. G. Coherent Conversion between Microwave and Optical Photons—an Overview of Physical Implementations. <i>Adv. Quantum Technol.</i> <b>2020</b>, <i>3</i> (1), 1900077.<br/>[4] Aliev, A. E.; Xiong, K.; Cho, K.; Salamon, M. B. Reversible Superconductivity in Electrochromic Indium-Tin Oxide Films. <i>Appl. Phys. Lett.</i> <b>2012</b>, <i>101</i> (25), 252603.<br/>[5] Mori, N. Superconductivity in Transparent Sn-Doped In<sub>2</sub>O<sub>3</sub>Films. <i>J. Appl. Phys.</i> <b>1993</b>, <i>73</i> (3), 1327–1338.<br/>[6] Batson, E. Reduced indium tin oxide as a transparent superconductor. https://hdl.handle.net/1721.1/144972 (accessed Sep 13, 2022).