Antiferrodistortive Reconstruction of thePbTiO3(001)Surface

Abstract

We present in situ x-ray scattering measurements of the surface structures of PbTiO(3) (001) in equilibrium with PbO vapor. At 875 to 1025 K, a reconstruction having c(2x2) symmetry is present under most conditions, while a 1 x 6 reconstruction occurs under PbO-poor conditions. The atomic structure of the c(2x2) phase is found to consist of a single layer of an antiferrodistortive structure with oxygen cages counter-rotated by 10 degrees about the titanium ions.

Novel high-temperature ferroelectric domain morphology in PbTiO3 ultrathin films

“…We used the adiabatic core-shell forcefield derived in Gindele et al, that reproduces the structural parameters of the cubic and tetragonal phases, the Born effective charge tensors, the elastic properties and soft phonon modes of PbTiO 3 in excellent agreement with density functional theory (DFT) calculations [25]. Furthermore, the model correctly describes the enhanced antiferrodistortive c(2x2) surface relaxation of PbTiO 3 in agreement with ab initio calculations [26,27].…”

“…It has recently been proposed that control of AFD chiralities could be used in novel technologies such as four-state memory making the identity of methods to control AFD behaviour at atomic scales paramount [45]. Here, we demonstrate the effects of ferroelectric-antiferrodistortive coupling between the c(2x2) AFD surface reconstruction and the ferroelectric (FE) closure domain patterns at the surface of the PbTiO 3 film [26,27]. This is characterised by the rotation of the equatorial oxygen atoms about the titanium, with simultaneous out-of-plane distortions which vary along the direction of the domain wall normals For the c d domains a sinusoidal dependence is noted with a maximum rotation at the centre of the domain when the polarisation is pointing out-of-plane and minimised when the polarisation points into the plane (Figure 5a).…”

Size dependence of nanostructures: Impact of bond order deficiency

“…For example, barium titanate particles are found to consist of a shell of cubic material surrounding a core of tetragonal material [380]. Although such a core-shell structure has not been reported in the PZT system, an antiferrodistortive reconstruction of the (001) surface layer of PbTiO 3 has been found by in situ X-ray scattering measurements [381]. It is easy to understand that the rotation of the relatively rigid oxygen octahedra decreases the lattice parameter or the distance between neighboring PbePb ions [382].…”

Investigations of Chemical Vapor Deposition of GaN Using Synchrotron Radiation

“…Above 800"C, the behavior is independent of temperature, and indicates a step-flow growth mode. The increase in the CTR intensity during step-flow growth indicates a change in the surface structure relative to the equilibrium (pre-growth) structure of GaN(OOOl) in NH3 [3], which we attribute to a reduction in the density of Ga vacancies in the surface layer. The CTR intensity decays monotonically during growth, and the decay rate increases significantly as temperature is decreased below 800°C.…”

“…We have applied this technique to investigating the epitaxial growth of GaN by metal-organic chemical vapor deposition (MOCVD). Our studies have included in situ measurements of surface structure in the MOCVD environment [2,3], real-time measurements of growth modes [4], faceting transitions [5], effects of impurities on growth [6], and wing tilt during lateral epitaxial overgrowth [7].…”