Photoinduced insulator-to-metal transition and surface statistics of VO_2 monitored by elastic light scattering

Abstract

Measurements of ultrafast light scattering within a hemisphere are performed for statistical analysis of nonequilibrium processes in VO2 epitaxial film. A Gerchberg-Saxton error reduction algorithm is applied for accurate calculation of a surface autocorrelation function from light scattering data and for partial reconstruction of a power spectral density function. Upon ultrafast photoinduced phase transition of VO2, the elastic light scattering reveals anisotropic grain-size-dependent dynamics. It was found that the transition rate depends on the optical absorption and orientation of VO2 grains with respect to polarization of the pump pulse. An observed stepwise evolution of surface autocorrelation length and transient anisotropy of the scattering field presumably originates from complex multistage transformation of VO2 lattice on a subpicosecond time scale.

Light scattering by epitaxial VO2 films near the metal-insulator transition point

“…26,55,56 This algorithm was also applied to restore absent PSD s (f) data at the periphery up to f ¼ 2.1 lm À1 and in the central area of the scattering indicatrix blocked by the sample holder [ Fig. 1(b)].…”

Ultrafast diffraction conoscopy of the structural phase transition in VO2 : Evidence of two lattice distortions

“…However, these techniques only partially resolve lattice relaxation dynamics, and many features remain hidden. After rigorous analysis of experimental data, several works [16,28,29,56,58] reported the presence of at least two stages of phase transition. Here, applying UDC technique the two stages of SPT process can be clearly resolved on a femtosecond time scale as shown in Fig.…”

“…Several studies of transient surface statistics [55,56] have shown the absence of coexistence of different VO 2 phases during the ultrafast phase transition. While slight variation of characteristic transition time was observed versus grain size, the pathway of SPT was identified as a coherent process across all spatial frequencies of the surface.…”

“…While slight variation of characteristic transition time was observed versus grain size, the pathway of SPT was identified as a coherent process across all spatial frequencies of the surface. Moreover, on femto-and picosecond time scales only short-range phonon interactions take place [55,56]. As a result, the ultrafast phase transition does not noticeably contribute to formation of new domains within several picoseconds.…”

Thermochromic light scattering from particulate VO2 layers

“…3,[12][13][14][15][16][17] Most optical applications of VO 2 require essentially non-scattering properties, and both films and nanoparticle composites have been subject to detailed studies recently. 13,15 Only a few prior investigations 9,[18][19][20][21][22][23][24][25] have considered light scattering, and we particularly note recent work by Jin et al 20,21 on diffuse transmittance through VO 2 -based functional fiber mats and by Moot et al 22 on composites of VO 2 and elastomers.…”