Strained state dynamics in a ${\text{VO}}_{2}$ thin film

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Strained state dynamics in a ${VO}_{2}$ thin film

T. Kikuzuki, R. Takahashi, and M. Lippmaa

Phys. Rev. B 82, 144113 – Published 20 October 2010

Abstract

The dynamics of a strain-induced resistive phase transition in a ${VO}_{2}$ thin film was studied by using a low-frequency crystal bending stage. It was found that the resistance response of the film to strain excitation is determined by two time constants, interpreted as a nucleation lifetime, in the $10^{- 6} - 10^{- 4} s$ range, and a domain growth lifetime of $\sim 10^{- 3} s$ . The variation of the domain nucleation lifetime is discussed in terms of the barrier height separating the coexisting insulating and metallic phases in a ${VO}_{2}$ film. Below the transition temperature, the phase transition is nucleation limited. Above the transition temperature, the resistance change is strongly affected by the growth of metallic domains. Direct imaging of metallic domains by local-probe current mapping showed that the phase transition in a thin film is limited by the presence of grain boundaries.

Received 17 May 2010

DOI:https://doi.org/10.1103/PhysRevB.82.144113

Authors & Affiliations

T. Kikuzuki, R. Takahashi, and M. Lippmaa^*

Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan

^*mlippmaa@issp.u-tokyo.ac.jp

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Vol. 82, Iss. 14 — 1 October 2010

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Figure 1
(Color online) X-ray diffraction pattern of a strained ${VO}_{2}$ film on a ${TiO}_{2} (001)$ substrate. The vertical dashed line marks the expected film peak position for a fully-strained epitaxial film. Inset shows a $0.5 μ m^{2}$ AFM topography image of the film surface. Measurements were done at room temperature with the film in the insulating state with a monoclinic structure.Reuse & Permissions
Figure 2
Resistance vs temperature of a ${VO}_{2}$ thin film grown on a ${TiO}_{2} (001)$ substrate. Free-energy profiles calculated by Vikhnin et al. (Ref. 16) are shown in terms of the charge-transfer order parameter, $q$ for the tetragonal symmetry, i.e., $q$ is bigger in the metallic phase, which is energetically favored when $T > T_{c}$ .Reuse & Permissions
Figure 3
(Color online) [(a)–(h)] Conducting-tip AFM current map images covering a $1 \times 1 μ m^{2}$ area, measured during cooling of a ${VO}_{2}$ film sample from 307 to 303.5 K. The measurement temperature for each map is shown in the image label. The mapping was done at a tip bias of $- 1 V$ . Light (blue) regions correspond to insulating domains and dark (red) dots show the appearance of the metallic state. The light blue tails surrounding metallic domains are caused by the limited bandwidth of the AFM tip current detector but correspond to tip currents that are below the threshold used for domain size determination. (i) A histogram of metallic domain sizes measured from images (a)–(d). Vertical dashed lines mark integer multiples of the average grain size of $342 {nm}^{2}$ , determined from the topography image. Based on the minimum detectable feature size, the image resolution is limited by the 128 pixel square imaging raster.Reuse & Permissions
Figure 4
(a) Compressive $c$ -axis strain applied to a film by flexing the substrate at 1 kHz and (b) the corresponding film resistance change. Schematic views of the deformation states are also shown (Ref. 11). (c) Resistance response hysteresis under harmonic strain excitation, replotted from (a) and (b).Reuse & Permissions
Figure 5
(a) Fitting the time dependence of resistance after a stepwise strain excitation at $T_{c}$ with Eq. (1) suggests a double exponential response function. (b) Frequency dependence of strain response amplitude (circles) and phase shift (squares) at $T_{c}$ , together with fitting curves.Reuse & Permissions
Figure 6
Measurement resistance (temperature) dependence of the (a) $α$ and (b) $τ_{1}$ , and $τ_{2}$ parameters. Open markers correspond to values obtained from frequency-domain measurements as shown in Fig. 5b. Filled markers and dotted lines correspond to time-domain data as shown in Fig. 5a. The horizontal dashed line in (b) marks the time resolution limit of the time-domain measurement of $τ_{1}$ .Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Strained state dynamics in a ${VO}_{2}$ thin film

T. Kikuzuki, R. Takahashi, and M. Lippmaa

Phys. Rev. B 82, 144113 – Published 20 October 2010

Abstract

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Physical Review B

covering condensed matter and materials physics

Strained state dynamics in a VO2 thin film

T. Kikuzuki, R. Takahashi, and M. Lippmaa

Phys. Rev. B 82, 144113 – Published 20 October 2010

Abstract

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Strained state dynamics in a ${VO}_{2}$ thin film