Investigation of the nanodomain structure formation by piezoelectric force microscopy and Raman confocal microscopy in LiNbO3 and LiTaO3 crystals

Abstract

Piezoelectric force microscopy (PFM) and Raman confocal microscopy have been used for studying the nanodomain structures in congruent LiNbO3 and LiTaO3 crystals. The high-resolution nanodomain images at the surface were observed via PFM. Raman confocal microscopy has been used for the visualization of the nanodomain structures in the bulk via layer-by-layer scanning at various depths. It has been shown experimentally that the nanodomain images obtained at different depths correspond to domain images at the polar surface obtained at different moments: the deeper the nanodomain, the earlier the moment. Such a correlation was applied for the reconstruction of the evolution of the domain structures with charged domain walls. The studied domain structures were obtained in highly non-equilibrium switching conditions realized in LiNbO3 and LiTaO3 via pulse laser irradiation and the electric field poling of LiNbO3, with the surface layer modified by ion implantation. The revealed main stages of the domain structure evolution allow the authors to demonstrate that all geometrically different nanodomain structures observed in LiNbO3 and LiTaO3 appeared as a result of discrete switching.

Microscopic texture characterisation in piezoceramics

“…This method is surface-sensitive, however the depth of penetration can be finely adjusted in semi-transparent materials by using defocussing techniques and a confocal probe. 102 The main problem with Raman is the interpretation of measured data, since a suitable texture-based model for the fitting of the collected spectral intensity is necessary. All in all, the combination of EBSD, laboratory XRD and Raman spectroscopy can be very powerful to analyse scale-dependent texture in piezoceramics, since these methods obtain information on comparable depth but with different spatial resolution.…”

Microscopic model of domain wall motion

“…Such a movement has been observed experimentally by several authors. 16,35,36 The growth of these new domains represents the polarization switching.…”

“…The simulation of the reversal of the polarization yields different stages of domain evolution, in agreement with experimental observations, namely: nucleation of new domains, forward growth, sideways growth, and domain coalescence observed in lithium niobate and lithium tantalate. 35,36 In our simulations, first a nucleus of a new domain is assembled with a probability depending on the local field. The nucleation starts with the reversal of one dipole next to the dead layer, most likely a dipole at the edge of the dipole plane.…”

Ferroelectric Domain Structure and Local Piezoelectric Properties of Lead-Free (Ka0.5Na0.5)NbO3 and BiFeO3-Based Piezoelectric Ceramics

“…The significant change of the Raman spectra (shifts and change of the intensity of the Raman bands) in the vicinity of the domain walls was shown in single crystals, thin films, and ceramics [9,51]. Moreover, the method allows not only the imaging of domain structure (Figure 4) [51], but also the extraction of information about mechanical stresses [85,86] and defect concentration [51]. Polarized Raman scattering can yield knowledge about the orientation of spontaneous polarization in distinct grains of ceramics [9,87].…”