AVS 51st International Symposium
    Nanometer-scale Science and Technology Friday Sessions
       Session NS-FrM

Paper NS-FrM11
Optical Properties of Ordered Arrays of Vanadium Dioxide Nanoparticles

Friday, November 19, 2004, 11:40 am, Room 213D

Session: Nanometer-scale Structures
Presenter: R. Lopez, Vanderbilt University
Authors: R. Lopez, Vanderbilt University
J.Y. Suh, Vanderbilt University
R.F. Haglund Jr., Vanderbilt University
L.C. Feldman, Vanderbilt University
Correspondent: Click to Email
Arrays of vanadium oxide nanoparticles with long-range order have been fabricated by pulsed laser deposition in an arbitrary pattern defined by focused ion-beam lithography. Interaction of light with the nanoparticles is controlled by the geometrical arrangement as well as by the differing optical properties displayed by the metallic and semiconducting phases of VO@sub 2@. The particle arrays present a previously unknown scattering resonance in the blue region of the spectrum. The scattering is pronounced in the semiconductor phase, but is less intense and slightly blue-shifted in metallic state. This phenomenon is intrinsically interesting, since previous studies of VO@sub 2@ switching have been confined to the IR region, whereas this configuration produces the relevant optical effects of the transition in the visible spectrum. In addition, the transition to the metallic state does not exhibit the usual step function at the critical temperature. Instead, the scattered light begins to increase in intensity at 68°C, the temperature of the bulk phase transition, and reaches a maximum before falling to a lower value in the metallic state resulting in a anomalous double loop hysteresis. This transient scattering enhancement results from the order-disorder transition that occurs as the nanoparticles are transformed by random fluctuations. The disorder or inhomogeneity present during this process enhances the scattering by coherent contributions of length scales longer than the array lattice constant, the necessary additional Fourier components to describe a disordered system. Arrays such as this open up new opportunities to study surface plasmon interactions for nanoparticles in close proximity, with the added advantage that the interaction can be switched on by the thermally driven metal-semiconductor phase transition in VO@sub 2@.