Observation of a Near-Surface Structural Phase Transition inSrTiO3by Optical Second Harmonic Generation

Abstract

A near-surface structural phase transition on a SrTiO3 single crystal, occurring at T(*) about 45 K above the bulk cubic-to-tetragonal transition, is observed by means of optical second harmonic generation. The temperature dependence of the second harmonic field in the vicinity of T(*) is described with a phenomenological Landau-type model.

Highly mobile vortex structures inside polar twin boundaries in SrTiO3

“…20 Subsequent experimental studies using transmission electron microscopy 22 and second harmonic generation (SHG) confirmed such wall polarity. 23,24 Similar behavior was attributed to multidomain boundaries with distinct polar and oxygen octahedral tilting in BiFeO 3 ab initio simulations. 25 The latest experimental advance was reported 26 in resonant piezoelectric spectroscopy (RPS) experiments for strontium titanate at cryogenic temperatures, well below the ferroelastic transition (105 K).…”

Correlation between surface rumpling and structural phase transformation in SrTiO3

“…The phase transition involves the rotation of TiO 6 octahedra and has been featured as a classic example of a soft mode phase transition [24]. There have been conflicting reports [17][18][19][20][21][27][28][29] that a surface phase transition may occur at significantly higher temperature ~ 150 K and a second bulk phase transformations below ~70 K [25,26]. The "surface" structures of SrTiO 3 reported in ref.…”

Spectroscopic ellipsometry of SrTiO3 crystals applied to antiferrodistortive surface phase transition

“…Recently, a near-surface structural PT on a STO single crystal, occurring at T Ã at about 45 K above the bulk cubic-totetragonal transition, was reported on the base of optical second harmonic generation (SHG) experiments [23]. The temperature dependence of the second harmonic field is described using a phenomenological Landau-type model.…”

“…[24], temperature dependence of the surface order parameter h 0 as well as of the surface transition temperature T S calls for taking into account surface-induced terms in the expression for the free energy. Following Levanyuk and Minyukov [24] this gives, for the second order PT [23]:…”