Domain Structure Of Films Research Articles

Epitaxial synthesis of single-domain gallium phosphide on silicon

The aim of the work is to investigate different approaches for the growth of planar gallium phosphide layers on silicon by molecular beam epitaxy. Atomic force microscopy and reflection high energy electron diffraction were used to study surface morphology and estimate the film domain structure. Developed growth technique with the use of a low-temperature AlGaP/GaP seeding layer allowed us to achieve atomically flat pseudomorphic single-phase GaP on Si(001).

Three-Dimensional Numerical Modeling and Visualization of the Domain Structure in Films with Perpendicular Anisotropy

Three-dimensional numerical modeling of static domain structures in a Co(0001) film is performed for different values of an external magnetic field perpendicular to the surface of the film or lying in the plane of the film. Changes in the fine structure of domain walls, associated with the appearance, motion, and disappearance of Bloch lines and Bloch points, are considered in detail.

Molecular dynamics simulations of ferroelectric domain formation by oxygen vacancy

An oxygen vacancy, known to be detrimental to ferroelectric properties, has been investigated numerically for the potential uses to control ferroelectric domains in films using molecular dynamics simulations based on the first-principles effective Hamiltonian. As an electron donor, an oxygen vacancy generates inhomogeneous electrostatic and displacement fields which impose preferred polarization directions near the oxygen vacancy. When the oxygen vacancies are placed at the top and bottom interfaces, the out-of-plane polarizations are locally developed near the interfaces in the directions away from the interfaces. These polarizations from the interfaces are in opposite directions so that the overall out-of-plane polarization becomes significantly reduced. In the middle of the films, the in-plane domains are formed with containing 90° a1/a2 domain walls and the films are polarized along the [1 1 0] direction even when no electric field is applied. With oxygen vacancies placed at the top interface only, the films exhibit asymmetric hysteresis loops, confirming that the oxygen vacancies are one of the possible sources of ferroelectric imprint. It has been qualitatively demonstrated that the domain structures in the imprint films can be turned on and off by controlling an external field along the thickness direction. This study shows qualitatively that the oxygen vacancies can be utilized for tuning ferroelectric domain structures in films.

Magnetic properties of Co/Pd multilayered films on porous Al2O3 templates with developed cell substructure

We studied the structure and magnetic properties of porous multilayered Co/Pd films deposited on the templates of anodized Al2O3 with a specific surface morphology that is characterized by a cellular–porous structure with several pores inside each cell. X-ray diffraction analysis and reflectometry are used to study the peculiarities of the formation of phases in deposited films. The effect of morphological features of porous Co/Pd films on their magnetoanisotropic properties and magnetization reversal processes (magnetization reversal mechanisms, domain structure of films, and coercive field H c ) is revealed by SQUID magnetometry and magnetic force microscopy.

Structure of micromagnetic formations arising on defects in garnet-ferrite films

Properties of magnetic inhomogeneities formed in magnetically uniaxial films on defects of certain types have been investigated theoretically and experimentally. According to calculations, these inhomogeneities, which correspond to 0° domain walls, can be of two types that differ in size and energy. It is shown that type-II inhomogeneities, which are much greater in size than those of type I, can become stable formations in the plates of finite thickness. The results obtained are compared with the experimental observations of the domain structure of films of garnet ferrites. The possible contribution of type-II inhomogeneities to the processes of the static and dynamic magnetization reversal of real magnets has been considered.

Surface topography and crystal and domain structures of films of ferroelectric copolymer of vinylidene difluoride and trifluoroethylene

The crystallization of a copolymer from a solution at room temperature is found to lead to the formation of a metastable structure, characterized by the coexistence of ferroelectric and paraelectric phases. The fraction of the latter decreases after annealing above the Curie point. Atomic force microscopy (AFM) has revealed a difference in the surface topographies between the films contacting with air and the films contacting with a glass substrate. The microstructure of copolymer chains has been investigated by 19F NMR spectroscopy. The chain fragments with “defect” attached monomeric units are ejected to the surface. The character of the ferroelectric domains formed during crystallization and their size distribution are analyzed.

Large irreversible non-180° domain switching after poling treatment in Pb(Zr, Ti)O3 films

(111¯)/(111)-oriented rhombohedral Pb(Zr0.65Ti0.35)O3 films with different domain fractions were epitaxially grown on various single crystals. The volume fraction of (111)-polar-axis oriented domains in as-deposited films, Vpol.(as-depo.), was controlled by selecting a single crystal substrate with a different thermal expansion coefficient. Applying an electric field, referred to as “poling treatment”, resulted in irreversible non-180° domain switching from the (111¯)-oriented domain (non-polar-axis) to the (111)-oriented domain (polar-axis), which was observed by synchrotron X-ray diffraction. Remanent polarization (Pr) values were higher than those estimated using the proportional relationship with Vpol.(as-depo.). However, the experimental Pr values were in good agreement with the values estimated using the volume fraction of (111)-oriented domains after applying the poling treatment. In rhombohedral Pb(Zr0.65Ti0.35)O3 films, 30%−50% of the (111¯)-oriented domains switched irreversibly to (111)-oriented domains as a result of the poling treatment. The present results show that the domain structures of films may change dramatically after the poling process, and both before and after the poling state should be characterized in order to interpret polarization and piezoelectric behaviors. This study helps to clarify the ferroelectric and piezoelectric properties of Pb(Zr, Ti)O3 films after poling treatment.

Domain Structures in Films with Combined Magnetic Anisotropy. Two-Dimensional Simulation

The domain structure dependence on the uniaxial anisotropy constant has been considered in a micrometer-thick film by means of the two-dimensional micromagnetic simulation. The film has both uniaxial and tetra-axial magnetic anisotropies. The new type domain structures and walls caused by the tetra-axial anisotropy presence are predicted.

Two-dimensional micromagnetic simulation of domain structures in films with combined anisotropy

The transformation of the domain structure of micrometer-thick films with variations in the induced uniaxial anisotropy constant with the easy magnetization axis perpendicular to the film surface has been investigated using numerical micromagnetic simulation in the framework of a two-dimensional model of the magnetization distribution. The case where the tetra-axial crystallographic anisotropy exists in the film with uniaxial magnetic anisotropy has been considered. The transformation of the open domain structure into the structure with a magnetic flux closed inside the sample has been investigated in detail, and new types of 109-degree and 90-degree vortex-like domain walls and periodic domain structures have been obtained.

Resonant soft x‐ray scattering and reflectivity study of the phase‐separated structure of thin poly(styrene‐b‐methyl methacrylate) films

AbstractCombined soft X‐ray scattering and reflectometry techniques promise analysis of polymer thin film domain structure and composition without resorting to chemical modification or isotopic labeling. This work explores the capabilities of these techniques in polymer films of poly(styrene‐b‐methyl methacrylate) (P(S‐b‐MMA)). The results demonstrate that the techniques give detailed information on the domain structure of thin films using well‐known modeling procedures. Discrepancies were noted between the X‐ray optical parameters that are needed to best fit the reflectivity data to the model and the expected parameters. The sources of these discrepancies are discussed in terms of instrument configuration parameters, sample attributes, and, particularly, anisotropy of the chromophore parameters. The results show that fitting the soft X‐ray reflectivity data is much more sensitive to these X‐ray optical parameters than the soft X‐ray scattering data. Nevertheless, fits to both types of data yield quantitative measures of the polymer film's lamellar morphology that are consistent with each other and with literature values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

Magnetization of a garnet film through a change in its multidomain structure under circularly polarized light

An effect of photomagnetization of a (Tm${}_{2.4}$Bi${}_{0.6}$)(Fe${}_{3.9}$Ga${}_{1.1}$)O${}_{12}$ garnet film at $T$ $=$ 300 K caused by a change in the film multidomain structure is discovered. The photomagnetization ($\ensuremath{\Delta}M$) is induced by the action of a circularly polarized pulsed lasing (power $P$ 600 kW/cm${}^{2}$, pulse duration ${\ensuremath{\tau}}_{\mathrm{i}}$ \ensuremath{\sim} 7 ns) in a wavelength range of 450 nm to 600 nm. The effect is measured vs the power and polarization of light and vs the magnetic field perpendicular to the film surface. Without a magnetic field the value of $\ensuremath{\Delta}M$ is the maximum for the circular polarization of light (0.1 G $\ensuremath{\Delta}M$ 1 G at a power of 300 kW/cm${}^{2}$). With a change of the polarization direction $\ensuremath{\Delta}M$ changes sign (for linear polarization $\ensuremath{\Delta}M$ $=$ 0). Our study of photomagnetization in external magnetic fields and observation of the film domain structure behavior led us to the conclusion that the effect is unambiguously attributed to a change in the multidomain structure of film by the action of light.

Electric-field induced ferromagnetic domain changes in exchange biased Co–BiFeO3 composites

We present direct observations of electric-field induced changes in the local ferromagnetic (F) domain structure in films formed from inclusions of F cobalt in an antiferromagnetic host of BiFeO3. Piezoelectric force microscopy was used to demonstrate that the composite Co–BiFeO3 films display ferroelectricity. Strikingly, magnetic contrast changes in magnetic force microscopic images were found with the application of a perpendicular electric field. These are the results of an exchange interaction between Co and BiFeO3.

Domain structure of (100)/(001)-oriented epitaxial PbTiO3 thick films with various volume fraction of (001) orientation grown by metal organic chemical vapor deposition

(100)/(001)-oriented epitaxial PbTiO3 films thicker than 1 μm were grown on various types of substrates by chemical vapor deposition. The domain structures of these films with different volume fractions of (001) were investigated. Domain structures, consisting of (100)/(001)-oriented domains, were observed regardless of the type of substrate. However, the tilting angles of the a- and c-domains from the surface normal linearly changed with the volume fraction of the (001) orientation. These results suggest that the volume fraction of the (001) orientation is crucial in identifying the domain structure of PbTiO3 thick films.

Observation of the magnetic domain structure in Cu0.47Ni0.53 thin films at low temperatures

We report on the first experimental visualization of domain structure in films of weakly ferromagnetic Cu0.47Ni0.53 alloy with different thickness at liquid helium temperatures. Improved high-resolution Bitter decoration technique was used to map the magnetic contrast on the surface of the films well below the Curie temperature TCurie (∼60 K). In contrast to magnetic force microscopy, this technique allowed visualization of the domain structure without its disturbance while the larger areas of the sample were probed. Maze-like domain patterns, typical for perpendicular magnetic anisotropy, were observed. The average domain width was found to be about 100 nm.

Interfacial Organizations of Gel Phospholipid and Cholesterol in Bovine Lung Surfactant Films

Pulmonary surfactants stabilize the lung by way of reducing surface tension at the air-lung interface of the alveolus. 31P NMR, thin-layer chromatography, and electrospray ionization mass spectroscopy of bovine lipid extract surfactant (BLES) confirmed dipalmitoylphosphatidylcholine (DPPC) to be the major phospholipid species, with significant amounts of palmitoyl-oleoylphosphatidylcholine, palmitoyl-myristoylphosphatidylcholine, and palmitoyl-oleoylphosphatidylglycerol. BLES and DPPC spread at the air-water interface were studied through surface pressure area, fluorescence, and Brewster angle microscopy measurements. Langmuir-Blodgett films of monomolecular films, deposited on mica, were characterized by atomic force microscopy. BLES films displayed shape, size, and vertical height profiles distinct from those of DPPC alone. Calcium ions in the subphase altered BLES film domain structure. The addition of cholesterol (4 mol %) resulted in the destabilization of compressed BLES films at higher surface pressures (>40 mN m-1) and the formation of multilayered structures, apparently consisting of stacked monolayers. The studies suggested potential roles for individual surfactant lipid components in supramolecular arrangements, which could be the contributing factors in pulmonary surfactant to attain low surface tension at the air-water interface.

Electromagneto-optical effects on local areas of a ferrite-garnet film

The electromagneto-optical (EMO) effect from separate magnetic domains in the epitaxial films of yttrium-ferrite-garnet is investigated simultaneously with visual control of the film's domain structure. The local EMO effect, both from single domain sites and from the sites with a domain wall is measured. These local effects are different from the EMO from the multidomain area of a film. It was revealed unexpectedly that a local value of the EMO effect for the domain magnetized along the applied magnetic field decreased drastically in the magnetization stage connected with vanishing of the domains with opposite sign of magnetization. In the homogeneously magnetized film, the EMO effect is practically absent. It is concluded that the electric field practically does not modify the film magnetization and the local EMO effect is connected with the influence of the electric field on the magnetic anisotropy parameter of the studied film.

The Properties of Ferroelectric Domain of PLT Thin Films Prepared by RF Magnetron Sputtering

AbstractLanthanum-modified lead titanate (PLT) ferroelectric thin films were fabricated by the RF magnetron sputtering system on Pt/Ti/SiO2/Si(100) substrates. The x-ray diffraction (XRD) patterns of the PLT films showed that the pure perovskite structure was formed in the PLT thin films. The Piezoresponse Force Microscopy (PFM) was used for determining the domain structure of these films. It was found that the 90 degree domain was the main domain structure of PLT thin films. It was found that the PLT films prepared by RF sputtering have relatively large pyroelectric coefficient γ=2.20×10-8C·(cm2·K)-1 and relatively high figures of merit for current responsivity, voltage responsivity and specific detectivity.

Microstructure and properties of single crystal BaTiO3 thin films synthesized by ion implantation-induced layer transfer

Single crystal BaTiO3 thin films have been transferred onto Pt-coated and Si3N4-coated substrates by the ion implantation-induced layer transfer method using H+ and He+ ion coimplantation and subsequent annealing. The transferred BaTiO3 films are single crystalline with root mean square roughness of 17nm. Polarized optical and piezoresponse force microscopy (PFM) indicate that the BaTiO3 film domain structure closely resembles that of bulk tetragonal BaTiO3 and atomic force microscopy shows a 90° a–c domain structure with a tetragonal angle of 0.5°–0.6°. Micro-Raman spectroscopy indicates that the local mode intensity is degraded in implanted BaTiO3 but recovers during anneals above the Curie temperature. The piezoelectric coefficient, d33, is estimated from PFM to be 80–100pm∕V and the coercive electric field (Ec) is 12–20kV∕cm, comparable to those in single crystal BaTiO3.

Model of the plane laminar PbTiO3 thin film domain structure on MgO substrate

Superstructure formation is examined as a strain relaxation mechanism for polydomain structure in an “utlrathin” film on a cubic substrate. A phenomenological model of the dielectric and mechanical behavior of the ferroelectric PbTiO3 film on an MgO oxide substrate is proposed. The case of a laminar 90° domain structure with the walls tilted to 45° with respect to the film/substrate interface is considered. Taking account an inhomogeneous film–substrate coupling related to the superstructure formation and a dislocation propagation mechanism, we investigate strain relaxation and its effect on the domain structure, electrical and mechanical properties as a function of the film thickness, and temperature. It is shown that evolution of the aa-domain abundance in utlrathin film can be related to the film–substrate coupling mechanism expressed in terms of an external to the film inhomogeneous field. Its variation with the film thickness implies the existence of two distinct growth modes influencing the layer texture. For films with a thickness greater than 250 nm, aa-domains abundance is maximum and equal to 18%. For thinner films, c-domains become more stable and their proportion increases up to ∼100% with the appearance of a single domain structure. Numerical modeling of electrical polarization, total strain in both domains, and mean stress in the film is performed for different thicknesses.

Perpendicular magnetic anisotropy in CoPt3(111) films grown on a low energy surface at room temperature

Epitaxial (111)-oriented CoPt3 films were deposited on WSe2(0001) substrates at room temperature using molecular beam epitaxy. We observed strong growth induced uniaxial perpendicular magnetic anisotropy which has a maximum of 3.2×106 erg/cm3 and coercivity of about 200 Oe for films with thicknesses <6 nm. At a thickness larger than 6 nm the easy magnetization axis progressively rotates into the plane of the film as the film thickness is increased. The magnetic domain structure in films with perpendicular magnetic anisotropy was investigated by photoemission electron microscopy revealing a characteristic thickness dependence near the reorientation transition.