Complex oxides: Vanadium Oxide

(a)Resistance versus temperature curve of a metal to insulator transition of a large area VO2 thin film.
(b)Same as (a) but the area of the film is sub-micron. Avalanches are visible in this regime.
(c)Binning of the jumps by size shows that there are more smaller jumps than larger ones and that this relation follows a power law.
(d)Picture of the sample with contacts on top of it.

VO2 is a unique complex oxides due to its enhanced electron–electron interaction which has a major influence on the electric properties. VO2 exhibits a sharp electronic transition from an insulating state (room temperature) to a metallic state (high temperature) see Fig 1a. This transition is highly coupled with a structural transition above a temperature of 340 K.

The metal–insulator transition (MIT) in vanadium dioxide has been known for decades. Recently we were able to measure the transition at sub-micron scales, see fig. 1b,d. Our measurements indicate a self-organized critical behavior at the MIT which exhibites avalanches and percolation (Fig 1c).

Other vanadium oxides also exhibit a MIT. V2O3 is a particular case where the MIT shows up around 150 K and an additional paramagnetic-antiferromagnetic transition occurs. First attempts at growth of a single-phase thin film show a 6 orders of magnitude change in resistance (fig 2 below).

Resistance versus temperature curve for V2O3 showing a six order of magnitude transition in resistivity.

[1] A. Sharoni, J. G. Ramirez, and Ivan K. Schuller , Phys. Rev. Lett. 101, 026404 (2008).

[2] J. -G. Ramírez, A. Sharoni, Y. Dubi, M. E. Gómez, and Ivan K. Schuller, Phys. Rev. B 79, 235110 (2009)

(c) 2007 Ivan K. Schuller       -       designed by Thomas Gredig