Structural and magnetic characterization of BaTiO3–BaFe12O19 bilayer thin films: Interface effects on the magnetic properties of barium hexaferrite layer

We report the successful growth of BaFe₁₂O₁₉–BaTiO₃ (BaM-BTO) bilayer thin films using pulsed laser deposition, considering different crystallographic textures; BTO on (0001)-BaM and BaM on (100)-BTO. Our study involved the bilayers, the individual ferrite and titanate films, and the targets used in their growth. Raman spectroscopy and X-Ray diffraction were used to examine the structure of BaM-BTO thin films, indicating that there is no formation of impurity phases. The morphological characterization was made by scanning electron microscopy, and the magnetic behaviour was studied using SQUID magnetometry. The spontaneous magnetization, magnetic anisotropy constant, and anisotropy field were determined simultaneously from the magnetic hysteresis loop. In addition, we also studied the influence of different annealing temperatures over the magnetic behaviour of bare BaM and covered with BTO thin film. This allows to discern between the different magnetization reversal processes in bilayer systems, indicating a strong correlation between the anisotropy field and the coercive field, and an unusual linear relation of the anisotropy constant with the spontaneous magnetization. Our results indicate a direct influence of the BTO on the magnetic properties of the BaM phase, which places these composite bilayers as excellent candidates for the development of multifunctional devices.     

Mixed grains and orientation-dependent piezoelectricity of polycrystalline Nd-substituted Bi4Ti3O12 thin films

Polycrystalline Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin films were prepared on Pt/Ta/glass substrates by a pulsed laser deposition method. X-ray diffraction measurements revealed that the BNT thin films were preferentially oriented along the (117) direction although they possessed a polycrystalline structure. Good ferroelectric properties of the BNT thin film were observed with a remnant polarization of 13 μC/cm² (2 P_r ~26 μC/cm²). The fatigue resistance test exhibited that the ferroelectric polarization of the BNT thin film degraded significantly after around 10⁹ switching cycles, which can be attributed to its crystal structure. We investigated the surface morphology and ferroelectric domain structure by atomic force microscopy (AFM) and piezoresponse force microscopy (PFM), respectively. Interestingly, mixed grains consisting of long and circular shapes were observed on the BNT film surface, which corresponded to a- and c-axes orientations of crystal growth, respectively. The PFM study revealed that the piezoelectric coefficient (d₃₃) of the long grains was much larger than that of the circular grains.     

Preparation and properties of pure crystalline perovskite CeFeO3 thin films with vanadium doping

Cerium ferrite (CeFeO₃) thin films doped with vanadium (V:CeFeO₃) were grown on SiO₂ quartz glass and <100>‐oriented SrTiO₃ (STO) crystal substrates by the radio‐frequency magnetron sputtering method in this study. The effects of crystallization, substrate, and V‐doping on the quality, the magnetic property and the magneto‐optical property of as‐prepared films are investigated. V:CeFeO₃ film grown on STO substrate has better crystallinity and has better lattice integrity due to the higher lattice matching between substrate and film. The magnetic hysteresis loop and the magnetic circular dichroism spectra show that the magnetization strength and the magneto‐optical properties of V:CeFeO₃ films have the significant anisotropy. Moreover, V‐doping and the stress lead to the change in easy magnetization direction of film. It shows that the perovskite B‐site doping with transition‐metal ion has significant influence on the magnetic and the magneto‐optical properties of CeFeO₃ thin films.     

取向TS-1分子筛膜的合成与结构引导机理

通过壳聚糖的引导作用, 采用水热法在氧化铝载体上原位合成了b-轴取向的钛硅分子筛(TS-1)膜. 使用XRD、SEM等手段对所合成的TS-1膜进行了表征. 通过漫反射FT-IR和接触角的测定描述了壳聚糖薄膜的表面官能团、壳聚糖薄膜表面与合成液的相互作用. SEM结果表明, 在壳聚糖的引导下可得到b-轴取向的TS-1膜, 而直接在氧化铝载体上只能得到无序的TS-1膜层. XRD的测量结果表现了典型的TS-1结构. 漫反射FT-IR和接触角的测试结果表明, 由于壳聚糖表面官能团的作用, 其表面形成过渡层, 经过成核, 晶核生长得到片状TS-1晶体颗粒, 最后获得多层b-轴取向的TS-1膜.     

Sol-Gel Processing and Pyroelectric Properties of Highly Oriented Pb(Mg,Zn)1/3Nb2/3O3 Thin Films

Thin films of Pb(Mg,Zn)_1/3Nb_2/3O₃ (PMZN) were fabricated by spin casting the partially hydrolyzed Pb-Mg-Zn-Nb-O complex alkoxide sols on (111)Pt-coated MgO (100) planes. A strong preferential orientation of (100) perovskite was observed in the thin film derived from the sol exhibiting pseudoplastic behavior. A small-angle X-ray scattering experiment in the Porod region was performed to correlate the observed preferential orientation with the network structure of precursor in the PMZN sol. It was shown that weakly branched precursor systems led to highly oriented perovskite grains after thin-film formation. The highly (100) oriented PMZN film exhibited a larger pyroelectric coefficient (>2 μC/(cm²-K)) and pyroelectric figure-of-merit ( F _D > 4 × 10^1–4 Pa^−1/2) than the PMZN thin film having randomly oriented grains.     

Nucleation- or Growth-Controlled Orientation Development in Chemically Derived Ferroelectric Lead Zirconate Titanate (Pb(ZrxTi1−x)O3, x= 0.4) Thin Films

The profound influence of low-temperature processing steps, hitherto assumed benign from the viewpoint of texture development, is reported. On inclusion of a 400°C step and further heat treatment at 700°C, PZT (40/60) sol-gel thin films with a strong (111) texture were obtained. When the 400°C step was excluded, the films exhibited a strong (100) texture. The (111) PZT texture development is nucleation-controlled and is attributed to the solid-phase epitaxial effect. The (100) texture is considered growth-controlled in that (100) oriented grains grow preferentially so as to minimize surface energy.     

Crystallographic Orientation Dependence on Electrical Properties of (Bi,Na)TiO3‐based Thin Films

Orientation‐engineered (La, Ce) cosubstituted 0.94(Bi_0.5Na_0.5)TiO₃–0.06BaTiO₃ thin films were epitaxially deposited on CaRuO₃ buffered (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.35 single‐crystal substrates by pulsed laser deposition. The ferroelectric, piezoelectric, dielectric, and leakage current characteristics of the thin films were significantly affected by the crystallographic orientation. We found that the (001)‐oriented film exhibited the best ferroelectric properties with remnant polarization P_r = 29.5 μC/cm² and coercive field E_c = 7.4 kV/mm, whereas the (111)‐oriented film demonstrated the largest piezoelectric response and dielectric permittivity. The bipolar resistive switching behavior, which is predominantly attributed to a combined effect of ferroelectric switching and formation/rupture of conductive filaments, was observed. The conduction mechanisms were determined to be ohmic conduction and Poole–Frenkel emission at high‐ and low‐resistance states, respectively, in all the films.     

Texture effect on the electrochemical properties of LiCoO2 thin films prepared by PLD

LiCoO₂ thin films were prepared by pulsed laser deposition (PLD) on Pt/Ti/SiO₂/Si (Pt) and Au/MgO/Si (Au) substrates, respectively. Crystal structures and surface morphologies of thin films were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The LiCoO₂ thin films deposited on the Pt substrates exhibited a preferred (0 0 3) texture with smooth surfaces while the LiCoO₂ thin films deposited on the Au substrates exhibited a preferred (1 0 4) texture with rough surfaces. The electrochemical properties of the LiCoO₂ films with different textures were compared with charge-discharge, dQ/dV, and Li diffusion measurements (PITT). Compared with the (1 0 4)-textured LiCoO₂ thin films, the (0 0 3)-textured thin films exhibited relatively lower electrochemical activity. However, the advantage of the (1 0 4)-textured film only remained for a small number of cycles due to the relatively faster capacity fade. Li diffusion measurements showed that the Li diffusivity in the (0 0 3)-textured film is one order of magnitude lower than that in the (1 0 4)-textured film. As discussed in this paper, we believe that Li diffusion through grain boundaries is comparable to or even faster than Li diffusion through the grains.     

Growth control of RF magnetron sputtered SrRuO3 thin films through the thickness of LaNiO3 seed layers

SrRuO₃ (SRO) thin films were grown on SiO₂/Si substrates with different thickness of LaNiO₃ (LNO) seed layers by RF magnetron sputtering. Effects of LNO thickness on the grain orientation, surface morphology, magnetic behavior and electrical transport properties of SRO films were investigated. The orientation of SRO films transformed from (110)_pc to (001)_pc and the residual stress was released gradually with increasing the thickness (pc refers to the pseudo-cubic unit cell of SrRuO₃). SRO films with higher orientation grown on LNO exhibited more flat surface, higher saturation magnetization, and lower coercive field. The magnetic anisotropy was enhanced on thicker LNO due to the different states of residual stress. In addition, the temperature dependence of resistivity was promoted by the microstructural disorder. (110)_pc-oriented SRO monolayer electrode and (001)_pc-oriented SRO/LNO300 bilayer electrode own low room temperature sheet resistance of 0.38 Ω/□ and 0.26 Ω/□, respectively. The results indicate that the controllable SRO films can be used as not only good bottom electrodes but also promising templates to control the crystallographic orientations of various other perovskite-based functional materials.     

Nanostructured magnetic CoNiP electrodeposits: structure-property relationships

Magnetic CoNiP thin film alloys were electrodeposited from chloride baths. The effects of solution composition, solution pH and film thickness on the magnetic properties, microstructure and phases of electrodeposited CoNiP films were investigated. Solution pH and NaH₂PO₂ concentration significantly influenced the magnetic properties of CoNiP deposits. These films when deposited from solutions of pH <2.25 exhibited soft magnetic properties, whereas from solutions of pH >2.25, hard magnetic deposits (H_C,⊥≈2000 Oe and H_C,//≈1000 Oe) were obtained. X-ray diffraction revealed hcp structure consisting of nanocrystalline grains (∼50 nm) with preferred (002) planes as deposit P content and solution pH increased.     

Superconductivity in heavily B-doped diamond layers deposited on highly oriented diamond films

We deposited a [100]-oriented B-doped diamond layer by three methods to clarify the effects of film morphology on the transition from metallic to superconducting diamond. Heavily B-doped [100]-oriented diamond layers were deposited on [first method] undoped polycrystalline diamond films with [111] faces, [second method] highly oriented undoped diamond (HOD) thin films with a pyramidal surface, and [third method] thick undoped HOD films with a pyramidal surface. We confirmed that the B-doped layer in the third method was oriented in the [100] direction by scanning electron microscopy (SEM). The highest transition temperatures were T_c(onset) = 5.0 K and T_c(zero) = 3.1 K for the B-doped layer deposited on a thick HOD film with a pyramidal surface under a zero magnetic field. By contrast, T_c(onset) was 4.1 K for a heavily B-doped diamond layer deposited on a thin HOD film with a pyramidal surface, and was 3.9 K for a heavily B-doped diamond layer deposited on an undoped polycrystalline diamond film. These differences in T_c for our samples are affected by disorder and effective hole-carrier doping in each sample. Using the third method, we successfully deposited a high-quality B-doped [100] layer in three steps: (first step) depositing a [100] HOD film on a Si [100] substrate, (second step) depositing an HOD film with a pyramidal surface, and (third step) depositing a [100]-oriented B-doped layer. The change in the electronic states due to the B-doping of diamond films and the film morphology were investigated by x-ray photoelectron spectroscopy (XPS) measurements and band calculations.     

Enhanced visible-light catalytic activity of Au nanoparticles loaded c-axis oriented Bi2VO5.5 porous thin films

Au nanoparticles loaded c-axis oriented Bi₂VO_5.5 (BVO) porous thin films were prepared by using a simple spin-coating technique. The porous structures were formed through the hydrolysis of bismuth nitrate, Bi(NO₃)₃, one of the raw materials for synthesizing the BVO precursor solutions. The optimal photocatalytic rate of the porous thin film is three times more than that of pure BVO thin film. The enhancement of photocatalytic activity can be attributed to the Schottky barrier in the intimate interface between Au nanoparticles and BVO grains and the increase of absorption of light caused by surface plasmon resonance effect of gold nanoparticles. The possible degradation mechanism of Au–BVO-Methylene Blue system has been discussed based on the energy band structure and further trapping experiments. This study provides a simple method to prepare bismuth-containing oxide porous thin films without any pore-forming reagents, and the results suggest that the Au nanoparticles loaded BVO thin film is a promising candidate material for water or air treatment.     

3D crystallographic alignment of alumina ceramics by application of low magnetic fields

Non-cubic crystals exhibit anisotropic physical and functional properties. Microscopic crystallites as constituents of polycrystalline materials are randomly oriented, thus polycrystalline ceramics lack the anisotropic properties of their monocrystalline counterparts. We propose a technology that exploits the synergy between magnetic alignment and colloidal ceramics processing, and enables to independently tune the orientation of grains in different sample regions by infinitesimal magnetic fields (<10?mT). The grain pivot mechanism enables the emulation of single crystals, as well as the creation of large complex-shaped ceramic elements with designed crystallographic landscapes and spatially and directionally tuned properties. Ultra-high magnetic response arises from magnetic shape anisotropy of platelet-shaped seed crystallites coated with small amounts of iron oxide nanoparticles. To control crystallographic growth directions during subsequent annealing procedures, the seeds are dispersed and aligned in a matrix of chemically identical, but much finer spherical particles. This technology opens an avenue to remarkably improve structural and functional properties of ceramic elements employed in numerous industrial applications.     

Investigation of electromechanical distortions in gallium nitride by reflectance anisotropy spectroscopy

Real time reflectance spectroscopy has been used to investigate the extent and development of dielectric anisotropy during chemical beam epitaxy of gallium nitride on a GaAs(001) substrate using a low temperature aluminium nitride buffer layer. Reflection anisotropy between the [1&#x0304;10] and [110] directions indicates a strong cubic symmetry with bulk anisotropic strains of the order of 0.001. Post-growth reflectance measurements have been made to investigate electromechanical distortions in the gallium nitride epilayer when an electric field was applied in the [001] direction. The d₁₄ piezoelectric modulus of cubic gallium nitride is estimated to be 1.95 pm V⁻¹. Reflectance anisotropy spectroscopy is shown to be a sensitive method for the measurement of electromechanical effects in thin films, and in particular a novel method for investigating thin film semiconductor piezoelectric materials.     

Investigations on the matrix composite [BiFeO3(BFO)-ZnFe2O4 (ZFO)-SrFe12O19(SFO)]’s magneto-dielectric characteristics and its application of technology

Citrate auto-combustion method was employed to create Bi-perovskite (BFO), Zn-ferrite (ZFO) and Sr-hexaferrites (SFO) nanoparticles, which were then mixed up to form matrix composite which used to separate the lead metal ions from wastewater. Based on XRD peaks, the crystallite size was between 30 and 52 nm. The particles' FTIR spectra clearly show that each synthesized compound has unique functional groups. The samples had agglomeration, with each agglomerate including many grains, as shown by the SEM micrographs. The energy band gap of SFO was enhanced and reduced from 3.5 to 1.5 eV by adding BFO and ZFO. For magnetic study, T_C as well as μ_eff of BFO and ZFO were improved by adding SFO. While the dielectric properties for pure SFO was enhanced after adding BFO and ZFO in the nanocomposite, in this research paper author succeed in preparing nanosample with upgrading magnetic, optical and electric properties more than individual samples’ properties. The synthetic BFO/ZFO/SFO nanocomposite produced impressive results in the treatment of wastewater due to their enormous surface area, regulated size, well-defined structure, and high magnetic, optical and electric properties. Kinetic and isotherm analysis are applied to the experimental results. The high correlation coefficient indicates the adsorption of heavy metal ions, which is described by the Langmuir and Freundlich isotherms (R²). For the 97% removal of Pb (II) from wastewater at a contact duration of 40 min at room temperature and pH 7.     

Effect of Mechanical Constraint on Domain Reorientation in Predominantly {111}‐Textured Lead Zirconate Titanate Films

Ferroelectric/ferroelastic domain reorientation was measured in 2.0 μm thick tetragonal {111}‐textured PbZr_0.30Ti_0.70O₃ thin films using synchrotron X‐ray diffraction (XRD). Lattice strain from the peak shift in the 111 Bragg reflection and domain reorientation were quantified as a function of applied electric field amplitude. Domain reorientation was quantified through the intensity exchange between the 112 and 211 Bragg reflections. Results from three different film types are reported: dense films that are clamped to the substrate (as‐processed), dense films that are partially released from the substrate, and films with 3% volume porosity. The highest amount of domain reorientation is observed in grains that are misoriented with respect to the {111} preferred (domain engineered) orientation. Relative to the clamped films, films that were released from the substrate or had porosity exhibited neither significant enhancement in domain reorientation nor in 111 lattice strain. In contrast, similar experiments on {100}‐textured and randomly oriented films showed significant enhancement in domain reorientation in released and porous films. Therefore, {111}‐textured films are less susceptible to changes in properties due to mechanical constraints because there is overall less domain reorientation in {111} films than in {100} films.     

Control of Crystal Orientation and Piezoelectric Response of Lead Zirconate Titanate Thin Films Near the Morphotropic Phase Boundary

PbZr_0.53Ti_0.47O₃ (PZT) thin films with various preferred crystallographic orientations were synthesized on various substrates using pulsed laser deposition techniques. Larger piezoelectric displacement, which involved the bending vibration of the PZT film/substrate, was observed in randomly oriented PZT thin film than that in (100)- and (111)-preferred texture films. This result was discussed by correlation with the number of effective spontaneous polarization axes in the morphotropic phase boundary of the PZT system. Moreover, polarization fatigue was found to lower the electric-field-induced displacement significantly, indicating a large contribution of ferroelectric domain motion to the piezoelectric response of PZT thin films under bipolar drive.     

Electrodeposition of PbTe thin films from acidic nitrate baths

Electrodeposition of PbTe thin films from an acidic nitric bath was systematically investigated to understand the kinetics and the effect of electrodeposition conditions on film composition, crystallographic structure, texture and grain size. The electroanalytical studies employed initially with a rotating disk electrode to investigate the kinetics associated with Te, Pb and PbTe electrodeposition. The results indicated that the PbTe thin films were obtained by the underpotential deposition (UPD) of Pb atoms onto the overpotentially deposited Te atoms on a substrate.Based on these studies, PbTe thin films were potentiostatically electrodeposited using e-beam evaporated gold thin films on silicon substrate to investigate the effect of various deposition conditions on film composition and microstructure. The data indicated that the microstructure, composition and preferred film growth orientation of PbTe thin films strongly depended on the applied potential and electrolyte concentration. At −0.12 V, the film was granular, dense, and preferentially oriented in the [1 0 0] direction. At potentials more negative than −0.15 V, the film was dendritic and preferentially oriented in the [2 1 1] direction. A smooth, dense and crystalline film with nearly stoichiometric composition was obtained at −0.12 V from a solution containing 0.01 M HTeO₂⁺, 0.05 Pb²⁺ and 1 M HNO₃.     

脉冲准分子激光扫描沉积(PLD)高c轴取向V2O5/Si薄膜及结构分析

采用脉冲准分子激光大面积扫描沉积技术,在Si(111)单晶衬底上沉积了多晶V2O5薄膜,经300℃以上退火处理得到了具有高c-轴取向生长的V2O5膜。300℃以上热退火处理的薄膜表面具有正常的化学计量比（无氧缺位）,晶粒间界明显,晶粒呈针棒状,晶粒尺寸在100－200nm之间。采用X射线衍射（XRD）、Raman光谱（RS）、Fourier红外光谱（FT－IR）及透射电镜扫描附件（STEM）对沉积及不同温度下退火处理的样品进行了结构分析。研究结果表明：V2O5/Si薄膜经400℃热处理后表面部分处于低价态的钒离子已被氧化为V2O5。     

Fabrication and properties of ZnO/GaN heterostructure nanocolumnar thin film on Si (111) substrate

Zinc oxide thin films have been obtained on bare and GaN buffer layer decorated Si (111) substrates by pulsed laser deposition (PLD), respectively. GaN buffer layer was achieved by a two-step method. The structure, surface morphology, composition, and optical properties of these thin films were investigated by X-ray diffraction, field emission scanning electron microscopy, infrared absorption spectra, and photoluminiscence (PL) spectra, respectively. Scanning electron microscopy images indicate that the flower-like grains were presented on the surface of ZnO thin films grown on GaN/Si (111) substrate, while the ZnO thin films grown on Si (111) substrate show the morphology of inclination column. PL spectrum reveals that the ultraviolet emission efficiency of ZnO thin film on GaN buffer layer is high, and the defect emission of ZnO thin film derived from Zn_i and V_o is low. The results demonstrate that the existence of GaN buffer layer can greatly improve the ZnO thin film on the Si (111) substrate by PLD techniques.