Via pulsed laser deposition and post-annealing, high quality K-doped WO$_{\mathrm{3-y}}$ films with reproducible transport properties are obtained. A home built two-coil mutual inductance setup is used to probe the behavior of the films in the superconducting and normal state. The inverse penetration depths and dissipation peaks are measured as a function of temperature and field. Separately, via thin film deposition techniques, we report for the first time stable crystalline hexagonal WO$_{\mathrm{3}}$ on substrates. In order to tune the physical properties of the undoped material, we utilized an ionic liquid gating technique. We observe an insulator-to-metal transition, showing the ionic liquid gate to be a viable technique to alter the electrical transport properties of this material. By comparing the alkali and ionic liquid gated WO$_{\mathrm{3}}$, we conclude with some remarks regarding how superconductivity arises in this system.
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Authors
Phillip Wu
Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford Universit
Satoshi Ishii
Department of Applied Electronics, Tokyo University of Science, Katsushika-ku, Tokyo 125-8585, Japan
Kenji Tanabe
Department of Applied Electronics, Tokyo University of Science, Katsushika-ku, Tokyo 125-8585, Japan
Ko Munakata
Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford Universit
Robert H. Hammond
Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford Universit
Kazuyasu Tokiwa
Department of Applied Electronics, Tokyo University of Science, Katsushika-ku, Tokyo 125-8585, Japan
Theodore H. Geballe
Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford Universit
Malcolm R. Beasley
Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Geballe Laboratory for Advanced Materials, Stanford Universit
