arXiv subjects

Hsiang-Chun Hsing

Publications and source records attributed to Hsiang-Chun Hsing.

4 recordsLinked to original sources

arXiv2021

Strain control of the metal-insulator transition in epitaxial SrCrO$_{3}$ thin films

In the perovskite oxide SrCrO$_{3}$ the interplay between crystal structure, strain and orbital ordering enables a transition from a metallic to an insulating electronic structure under certain conditions. We identified a narrow window of oxygen partial pressure in which highly strained SrCrO$_{3}$ thin films can be grown using radio-frequency (RF) off-axis magnetron sputtering on three different substrates, (LaAlO$_{3}$)$_{0.3}$-(Sr$_{2}$TaAlO$_{6}$)$_{0.7}$ (LSAT), SrTiO$_{3}$ (STO) and DyScO$_{3}$ (DSO). X-ray diffraction and atomic force microscopy confirmed the quality of the films and a metal-insulator transition driven by the substrate induced strain was demonstrated.

cond-mat.mtrl-sci↗

arXiv2020

Controlling ferroelectric hysteresis offsets in PbTiO$_{3}$ based superlattices

Ferroelectric materials are characterized by degenerate ground states with multiple polarization directions. In a ferroelectric capacitor this should manifest as equally favourable up and down polarization states. However, this ideal behavior is rarely observed in ferroelectric thin films and superlattice devices, which generally exhibit a built-in bias which favors one polarization state over the other. Often this polarization asymmetry can be attributed to the electrodes. In this study we examine bias in PbTiO$_3$-based ferroelectric superlattices that is not due to the electrodes, but rather to the nature of the defects that form at the interfaces during growth. Using a combination of experiments and first-principles simulations, we are able to explain the sign of the observed built-in bias and its evolution with composition. Our insights allow us to design devices with zero built-in bias by controlling the composition and periodicity of the superlattices.

cond-mat.mtrl-sci↗

arXiv2019

Role of ferroelectric polarization during growth of highly strained ferroelectrics revealed by in-situ x-ray diffraction

Strain engineering of perovskite oxide thin films has proven to be an extremely powerful method for enhancing and inducing ferroelectric behavior. In ferroelectric thin films and superlattices, the polarization is intricately linked to crystal structure, but we show here that it can also play an important role in the growth process, influencing growth rates, relaxation mechanisms, electrical properties and domain structures. We have studied this effect in detail by focusing on the properties of BaTiO$_{3}$ thin films grown on very thin layers of PbTiO$_{3}$ using a combination of x-ray diffraction, piezoforce microscopy, electrical characterization and rapid in-situ x-ray diffraction reciprocal space maps during the growth using synchrotron radiation. Using a simple model we show that the changes in growth are driven by the energy cost for the top material to sustain the polarization imposed upon it by the underlying layer, and these effects may be expected to occur in other multilayer systems where polarization is present during growth. Our research motivates the concept of polarization engineering during the growth process as a new and complementary approach to strain engineering.

cond-mat.mtrl-sci↗

arXiv2015

In-situ x-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

In epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in-situ synchrotron x-ray diffraction during the growth of BaTiO$_3$/SrTiO$_3$ superlattices on SrTiO$_3$ substrates by off-axis RF magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO$_3$ substrates and 20nm SrRuO$_3$ thin films on SrTiO$_3$ substrates. These experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.

cond-mat.mtrl-sci↗