arXiv subjects

Zhenlin Luo

Publications and source records attributed to Zhenlin Luo.

17 recordsLinked to original sources

arXiv2026

Nitrogen doping induced metal-insulator transition with iso-symmetric character in rutile VO2

Metal-insulator transitions (MITs) in correlated oxides offer immense potential for next-generation Mottronic devices. However, their integration into practical applications is often hindered by the coupling of MITs with symmetry-lowering structural phase transitions, which limits switching speed and endurance. In this study, we engineered an iso-symmetric MIT on average in epitaxial rutile VO2 thin films via an in-situ nitrogen doping strategy. Nitrogen incorporation effectively suppresses V-V dimerization, enabling an iso-symmetric MIT, while preserving the original crystal symmetry. Furthermore, in-operando time-resolved optical reflectivity measurements revealed a shortened switching time in nitrogen-doped films, highlighting their enhanced performance. Our findings provide critical insights into the underlying mechanisms of MITs and introduce anion doping as a powerful tool for tailoring phase transitions in strongly correlated electron systems. This approach opens new avenues for the development of high-performance electronic and photonic devices.

cond-mat.mtrl-sci↗

arXiv2025

Ideal antiferroelectricity with large digital electrostrain in PbZrO3 epitaxial thin films

Antiferroelectrics exhibit reversible antipolar-polar phase transitions under electric fields, yielding large electrostrain suitable for electromechanical devices. Nevertheless, in thin-film form, the antiferroelectric behavior is often obscured by competing ferroic orders, resulting in slanted hysteresis loops with undesired remnant polarization, subsequently posing challenges in obtaining ideal antiferroelectricity and understanding their intrinsic electrical behavior. Here, atomistic models for controllable antiferroelectric-ferroelectric phase transition pathways are unveiled along specific crystallographic directions. Guided by the anisotropic phase transition and orientation design, we achieved ideal antiferroelectricity with square double hysteresis loop, large saturated polarization (~60 {\mu}C/cm2), near-zero remnant polarization, fast response time (~75 ns), and near-fatigue-free performance (~10^10 cycles) in (111)P-oriented PbZrO3 epitaxial thin films. Moreover, a bipolar and frequency-independent digital electrostrain (~0.83%) were demonstrated in this architype antiferroelectric system. In-situ X-ray diffraction studies further reveal that the large digital electrostrain results from intrinsic field-induced antiferroelectric-ferroelectric structural transition. This work demonstrates the anisotropic phase transition mechanism and ideal antiferroelectricity with large digital electrostrain in antiferroelectric thin films, offering a new avenue for applications of antiferroelectricity in nanoelectromechanical systems.

cond-mat.mtrl-sci↗

arXiv2025

Ferroelectricity in layered bismuth oxide down to 1 nanometer

Atomic-scale ferroelectrics are of great interest for high-density electronics, particularly field-effect transistors, low-power logic, and nonvolatile memories. We devised a film with a layered structure of bismuth oxide that can stabilize the ferroelectric state down to 1 nanometer through samarium bondage. This film can be grown on a variety of substrates with a cost-effective chemical solution deposition. We observed a standard ferroelectric hysteresis loop down to a thickness of ~1 nanometer. The thin films with thicknesses that range from 1 to 4.56 nanometers possess a relatively large remanent polarization from 17 to 50 microcoulombs per square centimeter. We verified the structure with first-principles calculations, which also pointed to the material being a lone pair-driven ferroelectric material. The structure design of the ultrathin ferroelectric films has great potential for the manufacturing of atomic-scale electronic devices.

cond-mat.mtrl-sci↗

arXiv2024

Robust Steganography with Boundary-Preserving Overflow Alleviation and Adaptive Error Correction

With the rapid evolution of the Internet, the vast amount of data has created opportunities for fostering the development of steganographic techniques. However, traditional steganographic techniques encounter challenges due to distortions in online social networks, such as JPEG recompression. Presently, research into the lossy operations of spatial truncation in JPEG recompression remains limited. Existing methods aim to ensure the stability of the quantized coefficients by reducing the effects of spatial truncation. Nevertheless, these approaches may induce notable alterations to image pixels, potentially compromising anti-steganalysis performance. In this study, we analyzed the overflow characteristics of spatial blocks and observed that pixel values at the boundaries of spatial blocks are more prone to overflow. Building upon this observation, we proposed a preprocessing method that performs overflow removal operations based on the actual overflow conditions of spatial blocks. After preprocessing, our algorithm enhances coefficient stability while minimizing modifications to spatial block boundaries, favoring image quality preservation. Subsequently, we employed adaptive error correction coding to reduce coding redundancy, thereby augmenting robustness and mitigating its impact on anti-steganalysis performance. The experimental results indicate that the proposed method possesses a strong embedding capacity, maintaining a high level of robustness while enhancing security.

cs.CR↗

arXiv2023

Super-tetragonal Sr4Al2O7: a versatile sacrificial layer for high-integrity freestanding oxide membranes

Releasing the epitaxial oxide heterostructures from substrate constraints leads to the emergence of various correlated electronic phases and paves the way for integrations with advanced semiconductor technologies. Identifying a suitable water-soluble sacrificial layer, compatible with the high-quality epitaxial growth of oxide heterostructures, is currently the key to the development of large-scale freestanding oxide membranes. In this study, we unveil the super-tetragonal Sr4Al2O7 (SAOT) as a promising water-soluble sacrificial layer. The distinct low-symmetric crystal structure of SAOT enables a superior capability to sustain epitaxial strain, thus allowing for broad tunability in lattice constants. The resultant structural coherency and defect-free interface in perovskite ABO3/SAOT heterostructures effectively restrain crack formations during the water-assisted release of freestanding oxide membranes. For a variety of non-ferroelectric oxide membranes, the crack-free areas can span up to a few millimeters in length scale. These compelling features, combined with the inherent high-water solubility, make SAOT a versatile and feasible sacrificial layer for producing high-quality freestanding oxide membranes, thereby boosting their potential for innovative oxide electronics and flexible device designs.

cond-mat.mtrl-sci↗

arXiv2021

Revealing the three-component structure of water with principal component analysis (PCA) on X-ray spectrum

Combining the principal component analysis (PCA) of X-ray spectrum with MD simulations, we experimentally reveal the existence of three basic components in water. These components exhibit distinct structures, densities, and temperature dependencies. Among the three, two major components correspond to the low-density liquid (LDL) and the high-density liquid (HDL) predicted by the two-component model, and the third component exhibits a unique 5-hydrogen-bond configuration with an ultra-high local density. As the temperature increases, the LDL component decreases and the HDL component increases, while the third component varies non-monotonically with a peak around 20 $^{\circ}$C to 30 $^{\circ}$C. The 3D structure of the third component is further illustrated as the uniform distribution of five hydrogen-bonded neighbors on a spherical surface. Our study reveals experimental evidence for water's unique three-component structure, which provides a fundamental basis for understanding water's special properties and anomalies.

cond-mat.soft↗

arXiv2020

Electric-field-controllable high-spin SrRuO3 driven by a solid ionic junction

Controlling magnetism and spin structures in strongly correlated systems by using electric field is of fundamental importance but challenging. Here, a high-spin ruthenate phase is achieved via a solid ionic chemical junction at SrRuO3/SrTiO3 interface with distinct formation energies and diffusion barriers of oxygen vacancies, analogue to electronic band alignment in semiconductor heterojunction. Oxygen vacancies trapped within this interfacial SrRuO3 reconstruct Ru-4d electronic structure and orbital occupancy, leading to an enhanced magnetic moment. Furthermore, an interfacial magnetic phase can be switched reversibly by electric-field-rectifying oxygen migration in a solid-state ionic gating device, providing a framework for atomic design of functionalities in strongly correlated oxides using a way of solid chemistry.

cond-mat.str-el↗

arXiv2019

Nanosecond Optically Induced Phase Transformation in Compressively Strained BiFeO3 on LaAlO3

Above-bandgap optical illumination induces a transformation from tilted tetragonal-like (T-like) and rhombohedral-like (R-like) phases to an untilted T-like phase in compressively strained BiFeO3. Optical excitation leads to an out-of-plane lattice expansion in the T-like phase. The transformation proceeds in regions with boundaries between the T-like and tilted R-like and tilted T-like phases, consistent with the motion of a boundary. The optically induced transformation indicates that there are new optically driven routes towards nanosecond-scale control of phase transformations in ferroelectrics and multiferroics.

cond-mat.mes-hall↗

arXiv2019

Observation of a Room Temperature Two-dimensional Ferroelectric Metal

Materials with reduced dimensions have been shown to host a wide variety of exotic properties and novel quantum states that often defy textbook wisdom1-5. Ferroelectric polarization and metallicity are well-known examples of mutually exclusive properties that cannot coexist in bulk solids because the net electric field in a metal can be fully screened by free electrons6. An atomically thin metallic layer capped by insulating layers has shown decent conductivity at room temperature7. Moreover, a penetrating polarization field can be employed to induce an ion displacement and create an intrinsic polarization in the metallic layer. Here we demonstrate that a ferroelectric metal can be artificially synthesized through imposing a strong polarization field in the form of ferroelectric/unit-cell-thin metal superlattices. In this way the symmetry of an atomically thin conductive layer can be broken and manipulated by a neighboring polar field, thereby forming a two-dimensional (2D) ferroelectric metal. The fabricated of (SrRuO3)1/(BaTiO3)10 superlattices exhibit ferroelectric polarization in an atomically thin layer with metallic conductivity at room temperature. A multipronged investigation combining structural analyses, electrical measurements, and first-principles electronic structure calculations unravels the coexistence of 2D electrical conductivity in the SrRuO3 monolayer accompanied by the electric polarization. Such 2D ferroelectric metal paves a novel way to engineer a quantum multi-state with unusual coexisting properties, such as ferroelectrics, ferromagnetics and metals, manipulated by external fields8,9.

cond-mat.mtrl-sci↗

arXiv2019

Moiré Engineering of Electronic Phenomena in Correlated Oxides

Moiré engineering has recently emerged as a capable approach to control quantum phenomena in condensed matter systems. In van der Waals heterostructures, moiré patterns can be formed by lattice misorientation between adjacent atomic layers, creating long range electronic order. To date, moiré engineering has been executed solely in stacked van der Waals multilayers. Herein, we describe our discovery of electronic moiré patterns in films of a prototypical magnetoresistive oxide La0.67Sr0.33MnO3 (LSMO) epitaxially grown on LaAlO3 (LAO) substrates. Using scanning probe nano-imaging, we observe microscopic moiré profiles attributed to the coexistence and interaction of two distinct incommensurate patterns of strain modulation within these films. The net effect is that both electronic conductivity and ferromagnetism of LSMO are modulated by periodic moiré textures extending over mesoscopic scales. Our work provides an entirely new route with potential to achieve spatially patterned electronic textures on demand in strained epitaxial materials.

cond-mat.mes-hall↗

arXiv2019

Strain engineering of epitaxial oxide heterostructures beyond substrate limitations

The limitation of commercially available single-crystal substrates and the lack of continuous strain tunability preclude the ability to take full advantage of strain engineering for further exploring novel properties and exhaustively studying fundamental physics in complex oxides. Here we report an approach for imposing continuously tunable, large epitaxial strain in oxide heterostructures beyond substrate limitations by inserting an interface layer through tailoring its gradual strain relaxation. Taking BiFeO3 as a model system, we demonstrate that the introduction of an ultrathin interface layer allows the creation of a desired strain that can induce phase transition and stabilize a new metastable super-tetragonal phase as well as morphotropic phase boundaries overcoming substrate limitations. Furthermore, continuously tunable strain from tension to compression can be generated by precisely adjusting the thickness of the interface layer, leading to the first achievement of continuous O-R-T phase transition in BiFeO3 on a single substrate. This proposed route could be extended to other oxide heterostructures, providing a platform for creating exotic phases and emergent phenomena.

cond-mat.mtrl-sci↗

arXiv2019

Polarity and spin-orbit coupling induced large interfacial exchange coupling an asymmetric charge transfer in iridate-manganite heterostructure

Charge transfer is of particular importance in manipulating the interface physics in transition-metal oxide heterostructures. In this work, we have fabricated epitaxial bilayers composed of polar 3d LaMnO3 and nonpolar 5d SrIrO3. Systematic magnetic measurements reveal an unexpectedly large exchange bias effect in the bilayer, together with a dramatic enhancement of the coercivity of LaMnO3. Based on first-principles calculations and x-ray absorption spectroscopy measurements, such a strong interfacial magnetic coupling is found closely associated with the polar nature of LaMnO3 and the strong spin-orbit interaction in SrIrO3, which collectively drives an asymmetric interfacial charge transfer and leads to the emergence of an interfacial spin glass state. Our study provides new insight into the charge transfer in transition-metal oxide heterostructures and offers a novel means to tune the interfacial exchange coupling for a variety of device applications.

cond-mat.mes-hall↗

arXiv2019

Controllable Defect Driven Symmetry Change and Domain Structure Evolution in BiFeO3 with Enhanced Tetragonality

Defect engineering has been a powerful tool to enable the creation of exotic phases and the discovery of intriguing phenomena in ferroelectric oxides. However, accurate control the concentration of defects remains a big challenge. In this work, ion implantation, that can provide controllable point defects, allows us the ability to produce a controlled defect-driven true super-tetragonal (T) phase with enhanced tetragonality in ferroelectric BiFeO3 thin films. This point defect engineering is found to drive the phase transition from the as-grown mixed rhombohedral-like (R) and tetragonal-like (MC) phase to true tetragonal (T) symmetry. By further increasing the injected dose of He ion, we demonstrate an enhanced tetragonality super-tetragonal (super-T) phase with the largest c/a ratio (~ 1.3) that has ever been experimentally achieved in BiFeO3. A combination of morphology change and domain evolution further confirm that the mixed R/MC phase structure transforms to the single-domain-state true tetragonal phase. Moreover, the re-emergence of R phase and in-plane stripe nanodomains after heat treatment reveal the memory effect and reversible phase transition. Our findings demonstrate the control of R-Mc-T-super T symmetry changes and the creation of true T phase BiFeO3 with enhanced tetragonality through controllable defect engineering. This work also provides a pathway to generate large tetragonality (or c/a ratio) that could be extended to other ferroelectric material systems (such as PbTiO3, BaTiO3 and HfO2) which may lead to strong polarization enhancement.

cond-mat.mtrl-sci↗

arXiv2013

Periodic elastic nanodomains in ultrathin tetrogonal-like BiFeO3 films

We present a synchrotron grazing incidence x-ray diffraction analysis of the domain structure and polar symmetry of highly strained BiFeO3 thin films grown on LaAlO3 substrate. We revealed the existence of periodic elastic nanodomains in the pure tetragonal-like BFO ultrathin films down to a thickness of 6 nm. A unique shear strain accommodation mechanism is disclosed. We further demonstrated that the periodicity of the nanodomains increases with film thickness but deviates from the classical Kittel's square root law in ultrathin thickness regime (6 - 30 nm). Temperature-dependent experiments also reveal the disappearance of periodic modulation above 90C due to a MC-MA structural phase transition.

cond-mat.mtrl-sci↗

arXiv2012

Atomic layer engineering of perovskite oxides for chemically sharp heterointerfaces

Advances in synthesis techniques and materials understanding have given rise to oxide heterostructures with intriguing physical phenomena that cannot be found in their constituents. In these structures, precise control of interface quality, including oxygen stoichiometry, is critical for unambiguous tailoring of the interfacial properties, with deposition of the first monolayer being the most important step in shaping a well-defined functional interface. Here, we studied interface formation and strain evolution during the initial growth of LaAlO3 on SrTiO3 by pulsed laser deposition, in search of a means for controlling the atomic-sharpness of the interfaces. Our experimental results show that growth of LaAlO3 at a high oxygen pressure dramatically enhances interface abruptness. As a consequence, the critical thickness for strain relaxation was increased, facilitating coherent epitaxy of perovskite oxides. This provides a clear understanding of the role of oxygen pressure during the interface formation, and enables the synthesis of oxide heterostructures with chemically-sharper interfaces.

cond-mat.mtrl-sci↗

arXiv2010

Low-Symmetry Monoclinic Phases and Polarization Rotation Path Mediated By Epitaxial Strain in Multiferroic BiFeO3 Thin Films

A morphotropic phase boundary driven by epitaxial strain has been observed in a lead-free multiferroic BiFeO3 thin films and the strain-driven phase transitions were widely reported to be iso-symmetric Cc-Cc ones by recent works. In this paper, we suggest that the tetragonal-like BiFeO3 phase identified in epitaxial films on (001) LaAlO3 single crystal substrates is monoclinic MC. This MC phase is different from MA type monoclinic phase reported in BiFeO3 films grown on low mismatch substrates, such as SrTiO3. This is confirmed not only by synchrotron x-ray studies but also by piezoresponse force microscopy measurements. The polarization vectors of the tetragonal-like phase lie in the (100) plane, not the (110) plane as previously reported. A phenomenological analysis was proposed to explain the formation of MC Phase. Such a low symmetry MC phase, with its linkage to MA phase and the multiphase coexistence open an avenue for large piezoelectric response in BiFeO3 films and shed light on a complete understanding towards possible polarization rotation paths and enhanced multiferroicity in BiFeO3 films mediated by epitaxial strain. This work may also aid the understanding of developing new lead-free strain-driven morphotropic phase boundary in other ferroic systems.

cond-mat.mtrl-sci↗

arXiv2008

Fabrication of the preferentially orientated LiNbO3 nanoparticles and their ferroelectric behaviors

(00l)-Oriented LiNbO3 ultra-thin film was fabricated on Pt/Ti/SiO2/Si substrate using pulsed laser deposition. The film shrunk into crystalline state nanoparticles that still kept (00l) preferential orientation as being annealed in the oxygen atmosphere at 500 oC for 2 hours. These LiNbO3 nanoparticles exhibited the ferroelectricity, showing asymmetrical hysteresis loop which might originate from the large internal field at the interface. These nanoparticles could be used for further studying on the size effects and the ferroelectricity of nanocrystal.

cond-mat.mtrl-sci↗