Surface versus bulk characterization of the electronic inhomogeneity in a VO {2} film - Condensed Matter > Strongly Correlated ElectronsReportar como inadecuado




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Abstract: We investigated the inhomogeneous electronic properties at the surface andinterior of VO {2} thin films that exhibit a strong first-order metal-insulatortransition MIT. Using the crystal structural change that accompanies a VO {2}MIT, we used bulk-sensitive X-ray diffraction XRD measurements to estimatethe fraction of metallic volume p^{XRD} in our VO {2} film. The temperaturedependence of the p$^{XRD}$ was very closely correlated with the dcconductivity near the MIT temperature, and fit the percolation theorypredictions quite well: $\sigma$ $\sim$ p - p {c}^{t} with t = 2.0$\pm$0.1and p {c} = 0.16$\pm$0.01. This agreement demonstrates that in our VO$ {2}$thin film, the MIT should occur during the percolation process. We also usedsurface-sensitive scanning tunneling spectroscopy STS to investigate themicroscopic evolution of the MIT near the surface. Similar to the XRD results,STS maps revealed a systematic decrease in the metallic phase as temperaturedecreased. However, this rate of change was much slower than the rate observedwith XRD, indicating that the electronic inhomogeneity near the surface differsgreatly from that inside the film. We investigated several possible origins ofthis discrepancy, and postulated that the variety in the strain states near thesurface plays an important role in the broad MIT observed using STS. We alsoexplored the possible involvement of such strain effects in other correlatedelectron oxide systems with strong electron-lattice interactions.



Autor: Y. J. Chang, J. S. Yang, Y. S. Kim, D. H. Kim, T. W. Noh, D.-W. Kim, E. OH, B. Kahng, J.-S. Chung

Fuente: https://arxiv.org/







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