Domain Dynamics in Piezoresponse Force Microscopy: Quantitative Deconvolution and Hysteresis Loop Fine Structure

Domain dynamics in the Piezoresponse Force Spectroscopy (PFS) experiment is studied using the combination of local hysteresis loop acquisition with simultaneous domain imaging. The analytical theory for PFS signal from domain of arbitrary cross-section is developed and used for the analysis of experimental data on Pb(Zr,Ti)O3 polycrystalline films. The results suggest formation of oblate domain at early stage of the domain nucleation and growth, consistent with efficient screening of depolarization field within the material. The fine structure of the hysteresis loop is shown to be related to the observed jumps in the domain geometry during domain wall propagation (nanoscale Barkhausen jumps), indicative of strong domain-defect interactions.Comment: 17 pages, 3 figures, 2 Appendices, to be submmited to Appl. Phys. Let

Graphoepitaxial growth of CeO2 thin films on tilted-axes NdGaO3 substrates by pulsed laser deposition

CeO2 thin films were grown on NdGaO3 tilted-axes substrates by pulsed laser deposition (PLD) showing three-dimensional graphoepitaxial (3DGE) growth in the whole studied range of substrate tilt angles γ = 5-27º. Deviations from the tangent dependence can be divided into a systematic negative part and local deviations near certain film tilt angles. The systematic deviation may be explained as the effect of completely-strained coherent growth of the bottom layers of CeO2 film. Minimization of the surface energy near the small-index crystallographic planes (012) and (013) may account for the local deviations from the calculated dependence. The width of the rocking curve and the lattice constant variation for the 3DGE CeO2 films increase almost linearly with the substrate tilt angle until 19º and decrease for higher γ. At different deposition rates the 3DGE CeO2 film exhibits three possible structures: (i) relaxed completely oxygenated films at very low deposition rate, (ii) completely strained well-oxygenated films at moderate deposition rates, and (iii) oxygen-deficient films consisting of two layers at high deposition rates. The deviations of orientation of the film from the 3DGE formula are set by the lattice constant c in the direction normal to the (110) SICP of the substrate, which, in turn, depends on oxygen deficiency and the level of strain, introduced into the film by lattice mismatch with the substrate.publishe

Growth, structural and mechanical analysis of a single crystal of L-prolinium tartrate: a promising material for nonlinear optical applications

A single crystal of L-prolinium tartrate (LPT), which is an organic non linear optical material, was successfully synthesized and grown using a slow evaporation solution growth technique (SEST). The crystal structure and lattice parameters of the crystal were confirmed by powder X-ray diffraction and it was found that it belongs to the monoclinic crystal system with beta = 100.380 and a noncentrosymmetric space group. The presence of strain in the grown ingot was calculated from powder X-ray diffraction measurements. The crystalline perfection was examined by high resolution X-ray diffractometry, which revealed that the crystal contained structural grain boundaries. The optical behavior of the grown specimen was analyzed by photoluminescence (PL) spectroscopy and its time resolved PL decay was calculated. The grown crystal adopted a step wise growth pattern with parallel striations, which was confirmed from the etching technique. Its ferroelectric and piezoelectric properties were also assessed. Its third order non linearity was assessed using an open aperture Z-scan technique. The thermal parameters of the LPT single crystal were calculated using a photopyroelectric technique. The mechanical strength of the single crystal at the micro level was observed by nanoindentation using the Oliver-Pharr method

New developments in Nanotechnology

No abstract available

Investigations on key aspects of solution growth L-Alanine strontium chloride trihydrate single crystal for non-linear optical and photonic applications

In the modern era materials with high NLO efficiency, better mechanical and thermal properties are on leading edge and highly demanded for their efficient use in optical communication and fibers optics. In the present course of work, authors have grown successfully single crystals of L-alanine strontium chloride trihydrate(LASRT) by slow evaporation solution and slow cooling techniques so as to meet the demand of industries. Structure of the grown crystal with lattice parameters were confirmed by employing powder XRD technique. Mechanical strain present in the lattice is determined as -7.066 x 10(-2) by Williamson-Hall relation. The newly grown crystals were subjected to HRXRD to assess crystal perfection and various types of defects. In this research, quality of the grown crystals is found moderately good. The specimen has better transmission nearly 44% as indicated by UV-Vis spectra. Various remarkable parameters like optical band gap, reflectance, refractive index, extinction coefficient and electrical susceptibility are determined. Some important electronic parameters are calculated by using Claussius-Mossottee relation. Thermal properties were also investigated in detail by subjecting the crystals to TGA/DTA measurements. By photo acoustic analysis, thermal diffusivity (alpha) is found 1.8816 x 10(-6) m(2)/s which indicates large heat bearable capacity of the grown sample. Mechanical stability of LASRT is determined larger than already reported LOMHCl and LLHBr single crystals by Nano-indentation technique. Results for nonlinear optical testing, crystalline perfection and optoelectronic parameters indicate its suitability for laser applications

Local bias induced ferroelectricity in manganites with competing charge and orbital order states

Perovskite-type manganites, such as Pr1-xCaxMnO3, La1-xCaxMnO3 and La1-xSrxMnO3 solid solutions, are set forth as a case study of ferroelectricity formation mechanisms associated with the appearance of site- and bond- centered orbital ordering which breaks structural inversion symmetry. Even though the observation of macroscopic ferroelectricity may be hindered by the finite conductivity of manganites, polarization can still exist in nanoscale volumes. We use Piezoresponse Force Microscopy to probe local bias induced modifications of electrical and electromechanical properties at the manganite surface. Clear bias-induced piezocontrast and local hysteresis loops are observed for La0.89Sr0.11MnO3 and Pr0.60Ca0.40MnO3 compounds providing convincing evidence of the existence of locally induced polar states well above the transition temperature of the CO phase, while the reference samples without CO behavior show no ferroelectric-like response. Such coexistence of ferroelectricity and magnetism in manganites due to the charge ordering (CO) under locally applied electric field opens up a new pathway to expand the phase diagrams of such systems and to achieve spatially localized multiferroic effects with a potential to be used in a new generation of memory cells and data processing circuits