Ying Liu

• Doctor of Philosophy
• PROBIST Postdoctoral Researcher (Co-funded Marie Curie) at Catalan Institute of Nanoscience and Nanotechnology

In the archetypal antiferroelectric PbZrO3, antiparallel electric dipoles cancel each other, resulting in zero spontaneous polarization at the macroscopic level. Yet in actual hysteresis loops, the cancellation is rarely perfect and some remnant polarization is often observed, suggesting the metastability of polar phases in this material. In this w...

Plastic deformation in ceramic materials is normally only observed in nanometre-sized samples. However, we have observed high levels of plasticity (>50% plastic strain) and excellent elasticity (6% elastic strain) in perovskite oxide Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3, under compression along <100>pc pillars up to 2.1 μm in diameter. The exte...

Ferroelectrics hold promise for sensors, transducers, and telecommunications. With the demand of electronic devices scaling down, they take the form of nanoscale films. However, the polarizations in ultrathin ferroelectric films are usually reduced dramatically due to the depolarization field caused by incomplete charge screening at interfaces, ham...

Ferroelectric flux-closures are very promising in high-density storage and other nanoscale electronic devices. To make the data bits addressable, the nanoscale flux-closures are required to be periodic via a controlled growth. Although flux-closure quadrant arrays with 180o domain walls perpendicular to the interfaces (V-closure) have been observed...

Although ferroelectric materials are characterised by their parallel arrangement of electric dipoles, in the right boundary conditions these dipoles can reorganize themselves into vortices, antivortices and other non-trivial topological structures. By contrast, little is known about how (or whether) antiferroelectrics, which are materials showing a...

Whereas ferroelectricity may vanish in ultra-thin ferroelectric films, it is expected to emerge in ultra-thin antiferroelectric films, sparking people’s interest in using antiferroelectric materials as an alternative to ferroelectric ones for high-density data storage applications. Lead Zirconate (PbZrO3, PZO) is considered the prototype material f...

The switching dynamics of antiferroelectric lead zirconate (PbZrO3) freestanding capacitors compared to their epitaxial counterparts is reported. Frequency dependence of hysteresis indicates that freestanding capacitors exhibit a lower dispersion of switching fields, lower residual polarization, and faster switching response as compared to epitaxia...

Whereas ferroelectricity may vanish in ultra-thin ferroelectric films, it is expected to emerge in ultra-thin anti-ferroelectric films, sparking people's interest in using antiferroelectric materials as an alternative to ferroelectric ones for high-density data storage applications. Lead Zirconate (PbZrO3) is considered the prototype material for a...

We report the switching dynamics of antiferroelectric Lead Zirconate (PbZrO3) free standing capacitors compared to their epitaxial counterparts. Frequency dependence of hysteresis indicates that freestanding capacitors exhibit a lower dispersion of switching fields, lower residual polarization, and faster switching response as compared to epitaxial...

Nanoscale small-volume metallic materials typically exhibit high strengths but often suffer from a lack of tensile ductility due to undesirable premature failure. Here, we report unusual room-temperature uniform elongation up to ~110% at a high flow stress of 0.6–1.0 GPa in single-crystalline <110>-oriented CoCrFeNi high-entropy alloy nanopillars w...

In the archetypal antiferroelectric PbZrO3, antiparallel electric dipoles cancel each other, resulting in zero spontaneous polarisation at the macroscopic level. Yet in actual hysteresis loops, the cancellation is rarely perfect and some remnant polarization is often observed, suggesting the metastability of polar phases in this material. In this w...

The core structures of dislocations are crucial for understanding the plastic deformation mechanisms and the functional properties of materials. Here, we use the scanning transmission electron microscopy imaging techniques of high-resolution high angle annular dark field and integrated differential phase contrast to investigate the atomic structure...

Plastic deformation in ceramic materials is normally only observed in nanometre-sized samples. However, we have observed unprecedented levels of plasticity (>50% plastic strain) and excellent elasticity (6% elastic strain) in perovskite oxide Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PIN-PMN-PT), under compression along <100> pc pillar...

2D electron gas at LaAlO3/SrTiO3 (LAO/STO) interfaces has emerged as an attractive platform for novel nanoelectronic devices. Control over the active functional interface by electrical or mechanical means in this regard is of special interest. A new means of electric‐field control by lateral gating of the interface and modification of its electroni...

Diamond is known to possess a range of extraordinary properties that include exceptional mechanical stability. In this work, it is demonstrated that nanoscale diamond pillars can undergo not only elastic deformation (and brittle fracture), but also a new form of plastic deformation that depends critically on the nanopillar dimensions and crystallog...

The present work studies the strengthening mechanisms of a creep-resistant Mg-0.5Gd-1.2Ca (at.%) alloy at both room and elevated temperatures. Although peak-ageing (T6) at 180 °C for 32 h led to a significant increase in room temperature strength due to the precipitation strengthening by three types of precipitates (Mg2Ca, Mg5Gd on prismatic planes...

[111]‐Oriented perovskite oxide films exhibit unique interfacial and symmetry breaking effects, which are promising for novel quantum materials as topological insulators and polar metals. However, due to strong polar mismatch and complex structural reconstructions on (111) surfaces/interfaces, it is still challenging to grow high quality [111] pero...

This paper reports on the real-time observation of mechanical stress-induced micro and nano domain evolution in a single crystal relaxor ferroelectric [011] poled 24PIN-PMN-PT “3-2 mode” nano-sized lamella. Mechanical loading in the [100] direction was applied to lamella in situ within a transmission electron microscope, with a [01¯1] viewing direc...

Ferroelectric flux-closure domains have attracted great attention due to their potentials in high density data storage. For their future applications, it is important to understand their evolution with different factors, such as misfit strain. In this work, a flux-closure domain consisting of a vertical 180° domain wall with two symmetric a domains...

Coexistence of two phases creates a morphotropic phase boundary in perovskite oxides, which can provide large piezoelectric response, generating it a well suited system for probe-based memories and actuator applications. The coexistence of two phases in thin films is proposed to be induced by epitaxial constraints from substrates or chemical compos...

Ferroelectricity is generally deteriorated or even vanishes when the ferroelectric films are downsized to unit cell scale. To maintain and enhance the polarization in nanoscale ferroelectrics are of scientific and technological importance. Here, giant polarization sustainability is reported in a series of ultrathin PbTiO3 films scaled down to three...

Flux-closure domain structures in ferroelectric thin films are considered to have potential applications in electronic devices. It is usually believed that these structures are stabilized by the depolarization field and the contact with electrodes tends to screen the depolarization field and may limit their formation. In this work, the influence of...

The Interactions of Ferroelectric Domain Walls and Crystallographic Defects in the PbTiO3 Films - Volume 23 Issue S1 - Y. Liu, Y. L. Tang, Y. L. Zhu, W. Y. Wang, X. L. Ma

Atomic Mapping of Domain Configurations in Ferroelectric Thin Films - Volume 23 Issue S1 - Y. L. Tang, Y. L. Zhu, Y. Liu, Y. J. Wang, X. L. Ma

Atomic Level Structural Modulations at the Negatively Charged Domain Walls in BiFeO3 Films - Volume 23 Issue S1 - W. Y. Wang, Y. L. Tang, Y. L. Zhu, Y. B. Xu, Y. Liu, Y. J. Wang, S. Jagadeesh, X. L. Ma

Although elastic strains, particularly inhomogeneous strains, are able to tune, enhance or create novel properties of some nanoscale functional materials, potential devices dominated by inhomogeneous strains have not been achieved so far. Here we report a fabrication of inhomogeneous strains with a linear gradient as giant as 10⁶ per metre, featuri...

Ferroelectric a1/a2 domain structure has great potentials in high dielectric capacitors and tunable microwave devices. Understanding its structure is crucial to better control the domain configurations for future applications. In this paper, PbTiO3 thin films with variant thicknesses are deposited on (110)-oriented GdScO3 substrates by Pulsed Laser...

Exotic domain states, like vortex, offer the promise of superior properties and the potential disclination strain is a key factor for their formation in ferroelectrics. Here we show that large scale arrays of four-state vortex domains can be obtained in rhombohedral BiFeO3 thin films grown on PrScO3 substrates by pulsed laser deposition. Cs-correct...

Ferroelectric thin films grown on high index substrates show unusual structural and switching dynamics due to their special strain states. Understanding the misfit relaxation behavior is crucial to facilitate the high index thin film growth with improved quality. In this paper, ferroelectric PbTiO3 thin films were grown on LaAlO3 (111) substrates b...

Effects of crystal tilt on the determination of the relative positions of different ion columns in compounds such as ferroelectric PbTiO3 are of critical importance, because the displacements of Ti and O relative to Pb correlate directly to the spontaneous polarization and ferroelectric properties. Here a study about the effects of small-angle crys...

Spatial coupling of ferroelectric domain walls and crystallographic defects in PbTiO3 films is directly visualized via aberration-corrected scanning transmission election microscopy (STEM) by Xiu-Liang Ma and co-workers in article 1600342. This is a schematic illustration based on atomic-scale STEM mapping showing the atomic configurations of the f...

Although the strong coupling of polarization to spontaneous strain in ferroelectrics would impart a flux-closure with severe disclination strains, recent studies have successfully stabilized such a domain via a nano-scaled multi-layer growth. Nonetheless, the detailed distributions of polarizations in three-dimensions (3D) and how the strains insid...

Revealing interactions between defects and domain walls is important for understanding the ferroelectric and piezoelectric behaviors of a ferroelectric film, especially when considering the trend of device downscaling. By means of aberration-corrected transmission electron microscopy, domain patterns resulting from the interactions between 90°/180°...

KTaO3 is an incipient ferroelectric with its properties influenced by defects and the purity. In this paper, we investigated the microstructures of KTaO3 by X-ray diffraction (XRD) and Cs-corrected scanning transmission electron microscopy (STEM). XRD and electron diffraction indicate that a second phase of K6Ta10.8O30 precipitates from the matrix....

Doped BaSnO 3 has arisen many interests recently as one of the promising transparent conducting oxides for future applications. Understanding the microstructural characteristics are crucial for the exploration of relevant devices. In this paper, we investigated the microstructural features of 0.001% La doped BaSnO 3 thin film using both conventiona...

Atomic structures of tail-to-tail negatively charged domain walls in BiFeO3 thin films are revealed via aberration-corrected transmission electron microscopy, as described in article 1500024 by Y.-L. Zhu, X. L. Ma, and co-workers. On (100) type charged domain walls, one-dimensional structural modulations are demonstrated, with lattice spacing and l...

Charged domain walls (CDWs) show great potentials to mediate the properties of ferroelectrics. Direct mapping of these domain walls at an atomic scale is of critical importance for understanding the domain wall dominated properties. Here, based on aberration-corrected scanning transmission electron microscopy, tail-to-tail CDWs at 71°, 109°, and 18...