Electronic structure of SrTi\(_{1-x}\)V\(_x\)O\(_3\) films studied by \({\it in\ situ}\) photoemission spectroscopy: Screening for a transparent electrode material

• Published in: arXiv.org
• Main Authors: Kanda, Tatsuhiko, Shiga, Daisuke, Yukawa, Ryu, Hasegawa, Naoto, Duy Khanh Nguyen, Cheng, Xianglin, Tokunaga, Ryosuke, Kitamura, Miho, Horiba, Koji, Yoshimatsu, Kohei, Kumigashira, Hiroshi
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 22.05.2021
• Subjects: Carrier density; Correlation; Electrode materials; Electronic structure; Elementary excitations; Energy gap; Insulators; Metal-insulator transition; Photoelectric emission; Photoelectron spectroscopy; Solid solutions; Spectra; Spectrum analysis; Thin films; Weight
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2105.10706

This study investigated the electronic structure of SrTi\(_{1-x}\)V\(_x\)O\(_3\) (STVO) thin films, which are solid solutions of strongly correlated transparent conductive oxide (TCO) SrVO\(_3\) and oxide semiconductor SrTiO\(_3\), using \({in situ}\) photoemission spectroscopy. STVO is one of the most promising candidates for correlated-metal TCO because it has the capability of optimizing the performance of transparent electrodes by varying \({x}\). Systematic and significant spectral changes were found near the Fermi level (\({E_{\rm F}}\)) as a function of \({x}\), while the overall electronic structure of STVO is in good agreement with the prediction of band structure calculations. As \({x}\) decreases from 1.0, spectral weight transfer occurs from the coherent band near \({E_{\rm F}}\) to the incoherent states (lower Hubbard band) around 1.0-1.5 eV. Simultaneously, a pseudogap is formed at \({E_{\rm F}}\), indicating a significant reduction in quasiparticle spectral weight within close vicinity of \({E_{\rm F}}\). This pseudogap seems to evolve into an energy gap at \({x}\) = 0.4, suggesting the occurrence of a composition-driven metal-insulator transition. From angle-resolved photoemission spectroscopic results, the carrier concentration \({n}\) changes proportionally as a function of \({x}\) in the metallic range of \({x}\) = 0.6-1.0. In contrast, the mass enhancement factor, which is proportional to the effective mass (\({m^*}\)), does not change significantly with varying \({x}\). These results suggest that the key factor of \({n/m^*}\) in optimizing the performance of correlated-metal TCO is tuned by \({x}\), highlighting the potential of STVO to achieve the desired TCO performance in the metallic region.