Electrical properties of PMN-33PT thin film at MPB

This paper presents a systematic investigation of the electric properties of epitaxial PMN-33PT thin film as a function of temperature and frequency. Complex impedance measurements were performed over the temperature range of 30–500 K and frequency range 20 Hz–1 MHz. Obtained results were corrected for the SRO series resistance. Ferroelectric hysteresis loops and electric field tunability of the real part of dielectric permittivity were measured in the 300 K–450 K temperature range and at a frequency of 1 kHz. The results of electrical field tunability of complex dielectric permittivity were approximated by Landau-Ginsburg-Devonshire theory frame by the Johnson relation. Meanwhile, ferroelectric hysteresis loop measurements of epitaxial PMN-33PT thin film shows a good hysteresis property with a remnant polarization of 2Pr (Formula presented.) 10 µC/cm2 and coercive field of 2Ec (Formula presented.) 12 kV/cm at temperature range from 300 K to 380 K

Strain Engineering of Electrical Conductivity in Epitaxial Thin Ba0.7Sr0.3TiO3 Film Heterostructures

Thin epitaxial films have a great potential to be used in real life applications, such as oxide-on-silicon. However, they often contain a large amount of defects, leading to an enhanced electrical conductivity. This could be desirable in some applications (i. e. memristors), but the mechanism is not fully understood. Here we report on the investigation of epitaxial barium strontium titanate thin films deposited on strontium titanate single crystal substrates (Ba0.7Sr0.3TiO3/SrRuO3//SrTiO3 heterostructures) with a controlled epitaxial strain. The impedance analysis allowed us to propose a model, which explains changes in the temperature dependence of the conductivity based on the strain-dependent anisotropic change of electron/hole mobility

Internal electrical and strain fields influence on the electrical tunability of epitaxial Ba0.7Sr0.3TiO3 thin films

Perpetual demand for higher transfer speed and ever increasing miniaturization of radio and microwave telecommunication devices demands new materials with high electrical tunability. We have investigated built in electrical and strain fields' influence on the electrical tunability in Ba0.7Sr0.3TiO3 thin film hetero- system grown by pulsed laser deposition technique. We observed the built in electrical field by local piezo-force microscopy (as deflected hysteresis loops) and macroscopic impedance analysis (as asymmetric tunability curves), with the calculated 88 kV/cm built in field at room temperature. Negative-1.4% misfit strain (due to clamping by the substrate) enhanced ferroelectric phase transition temperature in Ba0.7Sr0.3TiO3 thin film by more than 300 K. Built in fields do not deteriorate functional film properties- dielectric permittivity and tunability are comparable to the best to date values observed in Ba1-xSrxTiO3 thin films. (C) 2016 AIP Publishing LLC

The perfect soft mode:giant phonon instability in a ferroelectric

Previous studies of unstable ('soft') optical modes in ferroelectrics have reported minimum frequencies of 1 cm(-1) (30 GHz) for underdamped phonons. In this work we fabricate a cylindrical coaxial specimen and rectangular plate waveguide specimens of tris-sarcosine calcium chloride (TSCC) and follow its soft mode several orders of magnitude lower to 1 GHz. Below 30 GHz the relaxation time is probably characteristic of domain wall motion; the new theory of Pakhomov et al (2013 Ferroelectrics at press) predicts 0.5 THz far from T-C and a (T - T-C)/T-C dependence, in agreement with our experimental values. This discovery has implications for GHz electronics such as phased array radar or other voltage-tunable low-loss components. The mean-field frequency description of the soft mode response f(T) is supported via precision calorimetry on TSCC with and without Br-doping. The ferroelectric-antiferroelectric phase transition, previously suggested from high-pressure data, is confirmed at 45 K at 1 atm.</p

Proton and helium ions acceleration in near-critical density gas targets by short-pulse Ti:Sa PW-class laser

International audienceThe ability to quickly refresh gas-jet targets without cycling the vacuum chamber makes them a promising candidate for laser-accelerated ion experiments at high repetition rate. Here we present results from the first high repetition rate ion acceleration experiment on the VEGA-3 PW-class laser at CLPU. A near-critical density gas-jet target was produced by forcing a 1000 bar H $_2$ and He gas mix through bespoke supersonic shock nozzles. Proton energies up to 2 MeV were measured in the laser forward direction and 2.2 MeV transversally. He $^{2+}$ ions up to 5.8 MeV were also measured in the transverse direction. To help maintain a consistent gas density profile over many shots, nozzles were designed to produce a high-density shock at distances larger than 1 mm from the nozzle exit. We outline a procedure for optimizing the laser–gas interaction by translating the nozzle along the laser axis and using different nozzle materials. Several tens of laser interactions were performed with the same nozzle which demonstrates the potential usefulness of gas-jet targets as high repetition rate particle source.</jats:p