SrRuO3 (SRO) has emerged as a promising quantum material due to its exotic electron correlations and topological properties. In epitaxial SRO films, electron scattering against lattice phonons or defects has been considered as only a predominant mechanism accounting for electronic properties. Although the charge trapping by polar defects can also strongly influence the electronic behavior, it has often been neglected. Herein, we report strong interfacial charge trapping in ultrathin SRO films on SrTiO3 (STO) substrates probed by noise spectroscopy. We find that oxygen vacancies in the STO cause stochastic interfacial charge trapping, resulting in high electrical noise. Spectral analyses of the photoinduced noise prove that the oxygen vacancies buried deep in the STO can effectively contribute to the charge trapping process. These results unambiguously reveal that electron transport in ultrathin SRO films is dominated by the carrier number fluctuation that correlates with interfacial charge trapping.
This work is supported by the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) (NRF-2021R1C1C1011219 and NRF-2021R1A4A1032085). The work at Sejong University is supported by the Basic Science Research Program through NRF funded by the Ministry of Education (NRF-2020R1A6A1A03043435). The work at the University of Wisconsin\u2013Madison is funded by the Gordon and Betty Moore Foundation\u2019s EPiQS Initiative, Grant GBMF9065 to C.-B.E., and a Vannevar Bush Faculty Fellowship (N00014-20-1-2844).
