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Amos Sharoni - Israel

Correlated metal-oxides with insulator-metal transitions and their nano-scale properties


Many transition metal oxides exhibit spectacular Insulator-Metal-transitions (IMT) the manipulation of which is essential for their application as active device elements. However, such manipulation is hindered by lack of microscopic understanding of mechanisms involved in these transitions. The IMT, during which conductivity can change by many orders of magnitude, is generally first order, hysteretic and correlated with structural transitions and often inhomogeneous.

After a general introduction, I will describe a series of experiments done in VO2, a prototypical IMT material, to characterize the transition and the resulting importance of inhomogeneity in understanding the microscopic nature of the IMT. We have performed local transport, Hall, First Order Reversal Curve (FORC), impedance spectroscopy, and local temperature measurements. Interestingly, we find that the IMT occurs through a series of avalanches, with the avalanche exponent indicative of long-range interactions. High resolution Hall measurements provide interesting information on the characteristics of inhomogeneity, while FORC and impedance spectroscopy measurements confirm the presence of ‘filamentary’ transitions starting prior and continuing across the IMT.

Finally, I will briefly highlight recently developed nano-fabrication methods that are undamaging of the delicate transition metal oxide properties, crucial for integration of such materials into novel oxide-electronic devices.

This research is supported by the ISF.

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