Metalorganic Deposition Research Articles

Influence of chemical solution growth and vacuum annealing on the properties of (100) pseudocubic oriented BiFeO3 thin films

BiFeO3 (BFO), a Pb-free perovskite oxide, is being explored for its potential use in a multitude of applications. We report on the oriented growth of BFO thin films using a facile metal-organic chemical solution deposition. Unlike the growth characteristics observed in Si/SiO2 and glass/FTO substrates, the solution growth process on sapphire (0001) is found to yield highly oriented thin films along (100)pc planes. Furthermore, annealing in air (BFO-A) and high-vacuum (BFO-V) ambients are done to explore the tunable limits of its physical properties. Temperature-dependent Raman studies highlight the high quality of thin films with sharp changes in Raman modes around transition temperatures. In addition, the films exhibit a hitherto unreported anomalous shift in A1(TO) and E(TO) modes around 450 K. The bandgap of BFO-V (Eg = 2 eV) is lower than that of BFO-A (Eg = 2.12 eV) and exhibits an increased defect photoluminescence emission. The magnetization (M) is twofold higher for BFO-V [M ≈ 42 (67) emu/cm3 at 300 K (5 K)]. In-plane and out-of-plane M vs H plots show larger anisotropy and hard hysteresis for BFO-A compared to BFO-V. Piezoelectric switching with d33 values of 5–10 pm/V is the characteristic of BFO ferroelectric materials. Photoconductivity measurements show a one order increase due to vacuum annealing. Carrier generation and recombination lifetimes are twofold faster in BFO-V as compared to BFO-A thin films. The controllable physical properties of oriented BiFeO3 thin films will be useful in magnetoelectrics and photoferroelectrics applications.

Development of Flexible Electro Ceramics Films Prepared by Photo-Assisted Metal Organic Deposition (MOD) and its Electrical Component Application

Development of Flexible Electro Ceramics Films Prepared by Photo-Assisted Metal Organic Deposition (MOD) and its Electrical Component Application

Optimization of interim heat-treatment condition on TFA-MOD process for fabrication of Y0.77Gd0.23Ba2Cu3Oy coated conductors with BaHfO3

We have optimized the interim heat-treatment (IHT) time in trifluoroacetate based metal organic deposition process on fabrication of the BaHfO3 (BHO) doped Y0.77Gd0.23Ba2Cu3Oy (YGdBCO) coated conductor (CC) in order to further improve the in-field critical current density (Jc) performance. The in-field Jc values of 0.6 μm-thick BHO doped YGdBCO CCs increased with increasing the IHT time within 90 min. The highest critical current density (Jc) value of 0.86 MA/cm2 at 77 K in 3 T (B//c) was obtained for 0.6 μm-thick BHO doped YGdBCO CC with IHT time of 90 min. CCs with IHT time shorter than 90 min had relative low in-field Jc performance but high self-field Jc performance. It can be caused by the insufficient transformation to BaF2 in IHT which is a reason for the relatively large BHO particles. In the case of applying IHT for longer time than 90 min, coarsening of CuO particles in precursor films was suggested and degradation of self- and in-field Jc performances were observed.

Superconducting properties of (Y1−xEux)Ba2Cu3Oy-coated conductors prepared via trifluoroacetate–metalorganic deposition

In order to investigate the effect of the partial substitution of Y by Eu on the superconducting properties of REBa2Cu3Oy (RE: rare earth) films, we fabricated trifluoroacetete-metalorganic deposited Y1-xEuxBa2Cu3Oy, (x = 0.1, 0.23 0.3, 0.4, 0.5) films on metallic substrates with optimal crystallization conditions. The optimized crystallization conditions for fabricating Y1-xEuxBa2Cu3Oy coated conductors with high x composition are relatively high crystallization temperature and low oxygen pressure comparing with YBa2Cu3Oy. The films with high χ exhibit a high critical temperature, irreversible fields, and high critical current density in the high-magnetic region at 77 K. However, the superiority on the critical current density of the films with high χ in self and low fields at 77 K is not necessary conformed. This behavior might be explained by the influence of the melt-growth mode in the film with high x.

High Performance Coated Conductors Fabricated by UTOC-MOD Process

A new metal organic deposition (MOD) process using precursor solution containing metal trifluoroacetates was developed to improve in-field performance. In this process, the pinning centers of BaMO3 (M: metal elements such as Zr and Hf) materials could be made to be finer by reducing the once coating thickness in the coating and calcination step. This is referred to as the ultra-thin once coating (UTOC)-MOD process. This process improves the in-field performance. The UTOC-MOD process also has the advantage of uniformity of 2-dimensional Jc-distribution, which was determined using a scanning hall-probe microscopy analysis. Improvement of the Jc uniformity was also confirmed based on scribed tapes. A smaller dispersion of the filament-critical current values in the UTOC-MOD tape was determined based on a comparison with the results for obtained by a conventional process. With respect to the mechanical strength, it was established that the dispersion of the delamination strength, which was evaluated using stud-pull equipment, was suppressed. Microstructural analysis revealed that, the UTOC films were pore-free, although large pores are present in the films when conventional MOD is utilized. This difference in the microstructure can be attributed to the aforementioned improvement in the uniformity of the UTOC-MOD films.

Advance in Long-Length REBCO Coated Conductors Prepared by Reel-to-Reel Metalorganic Solution and Ion-Beam-Assisted Deposition

In the present work, we report our recent efforts to improve the homogeneity of MgO buffer layers and superconducting YBa 2 Cu 3 O 7-δ coated tapes prepared by ion-beam-assisted deposition and metalorganic solution deposition (MOD), respectively. Based on previous research results involving fluorine, a reduced atmospheric pressure is used for the MOD technique to improve the in-plane texture and suppress microcracks in the film, and then more than 500 m of MOD-coated superconducting tape is manufactured, exhibiting an excellent biaxial texture and superconducting performance. The full width at half maximum values for both in-plane and out-of-plane textured films are as low as 3° based on X-ray diffraction (XRD) measurements. The superconducting current-carrying capacities for 12-mm tapes are approximately 450-520 and 450-500 A for the 100-m level and 500-m level (77 K, self-field), respectively. The current-carrying capacities were measured by both reel-to-reel transport and an inductive system, and the results demonstrated that the cost-effective MOD technique is very promising for long-length high-quality coated conductors.

Effect of annealing temperature on the structural, morphological and optical properties of ThO2 thin films grown by photochemical metal–organic deposition

In this work, we report the influence of annealing temperature on the structural, morphological and optical properties of ThO2 thin films deposited on fused quartz and (100) silicon substrates by photochemical metal–organic deposition (PMOD) using hinokitiolate thorium (IV) complex as the precursor. X-ray photoelectron spectroscopy (XPS) confirmed the deposition of the ThO2 films. The effect of thermal annealing (from 300 °C to 1100 °C) on the structural properties of the ThO2 films was evaluated with X-ray diffraction (XRD), UV–Vis transmittance spectroscopy, spectroscopic ellipsometry and atomic force microscopy (AFM). XRD patterns of the films annealed above 300 °C revealed that all diffraction peaks belong to a cubic ThO2 structure without preferential orientation. The average crystallite size increased from 2.3 nm to 3.7 nm as the annealing temperature increased from 300 °C to 750 °C. Annealing at 1100 °C promoted the formation of huttonite (β-ThSiO4) in the ThO2 layer. Films deposited on fused quartz showed 80% transmittance in the visible range, and the annealing temperature did not impact the band gap energy. The AFM studies revealed that as the annealing temperature increased, the film surface roughness decreased. Between 750 °C and 950 °C, the film surface was relatively smooth with an of RMS surface roughness in the range 2.3–5.0 nm. The values of the refractive index of the films were in the range of n = 1.6 for the as-deposited film to n = 2.1 for the films annealed at 750 °C. This result suggests the potential use of ThO2 films as a transparent reflector material for short wavelengths.

Superconducting Joint of GdBa2Cu3Oy Coated Conductors by Crystallization of an Additionally Deposited Precursor Layer

A superconducting joint of REBa 2 Cu 3 O y (REBCO) coated conductors (CCs) has been demanded strongly to fabricate long length CCs for high field magnet applications such as nuclear magnetic resonance and magnetic resonance imaging. In the previous reports of superconducting joint, specimens of REBCO CCs were jointed via melting REBCO phases or via solid state diffusion of REBCO phases. In our study, we propose a new method of joint for REBCO CCs. A precursor layer is additionally deposited on GdBCO CC by a metal organic deposition process, and then two pieces of them are stuck together face-to-face and crystallized the precursor to form 123 phase under mechanical pressure in an oxygen atmosphere. The microstructures and temperature dependence of resistance of the jointed sample are characterized by a cross-sectional transmission electron microscopy (TEM) and a four-probe method, respectively. As a result, TEM observation reveals that two CCs are jointed together without formation of secondary phases at the joint interface. Also, temperature dependence of resistance shows Tc onset and Tc zero of 93 K and 82 K, respectively. Consequently, a superconducting joint has been completed successfully. The concept of this method is combining film growth and solid-state diffusion for the additionally deposited precursor layers.

MoS2 coating on CoSx-embedded nitrogen-doped-carbon-nanosheets grown on carbon cloth for energy conversion

Designing low-cost and highly efficient electrocatalysts has become a critical aspect to achieve sustainable energy production. Herein, we report the preparation strategy of MoS2 on Co-oxide nanoparticles embedded nitrogen-doped carbon nanosheets (Co-NC) those derived by ZIF-L anchored on a carbon cloth as an electrode for hydrogen evolution reaction (HER). The hybrid electrode denoted as MoS2/Co-NC/CC was synthesized in sequence of the growth of the leaf-like zeolitic imidazolate framework (Co-ZIF-L) on a carbon cloth (CC), the carbonization of the Co-ZIF-L and deposition of MoS2 by metal organic chemical deposition (MOCVD). The hierarchical porous catalyst presented remarkable electrochemical activity towards the HER in acidic solution, exhibiting great stability and fast kinetics with a small Tafel slope of 51 mV dec−1. Moreover, to produce a current density of 10 mA cm−2 (η10), MoS2/Co-NC/CC required a low overpotential of 111 mV, which is comparable with Pt.

Properties of Semipolar GaN Grown on a Si(100) Substrate

Semipolar GaN layers synthesized on a nanostructured Si(100) substrate are studied. It is shown that using a Si(100) nanoprofile combined with SixNy nanostrips on top of nanostructures can yield, via metal-organic chemical-vapor deposition, GaN(10 $$\bar {1}$$ 2) layers. An additional SiC buffer layer makes it possible to obtain GaN(10 $$\bar {1}$$ 1) layers with a full-width at half-maximum of the diffraction-curve of ωθ ≈ 35′ arcmin. It is found that the luminescence properties of the semipolar layers are mostly due to basal plane stacking faults BSFS-I1, in contrast to polar layers in which these properties are mostly due to the recombination of excitons.

Jahn-Teller reconstructed surface of the doped manganites shown by means of surface-enhanced Raman spectroscopy

We report direct evidence of the theoretically predicted electron-rich surface of doped perovskite manganites ${\mathrm{La}}_{0.7}{A}_{0.3}{\mathrm{MnO}}_{3}\phantom{\rule{4pt}{0ex}}(A=\text{Ca}$, Sr) by means of surface-enhanced Raman spectroscopy. The required Au nanoparticles were grown on top of thin manganite films by the metalorganic aerosol deposition technique, which provides a stable oxygen atmosphere and prevents deoxygenation effects. The acquired surface-enhanced Raman spectra of rhombohedral ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ thin films reveal the symmetry-forbidden Jahn-Teller stretching modes demonstrating the predicted symmetry breaking at the surface and fallback into the orthorhombic (Pnma) structure. This results in a unique Jahn-Teller reconstructed surface structure, which limits the capabilities of mixed-valence manganites in spintronic applications, but will be highly favorable for catalytic reactions.

Residual stress and strain on microstructure evolutions and superconductivity of REBa2Cu3O7−δ films grown by trifluoroacetate metal organic deposition

This research studies the effects of the residual stress and strain on the microstructure, critical current density, transition temperature, and microwave surface resistance of REBa2Cu3O7−δ (RE, rare earth) thin films grown by trifluoroacetate metal organic deposition. Different concentrations of Dy are introduced into YBa2Cu3O7−δ superconducting thin films. The superconducting transition temperature increases with an increase in the internal strain, while the critical current density exhibits an inverse variation relationship with the residual stress and c-axis length. The current carrying capability of REBa2Cu3O7−δ thin films can be improved by doping with appropriate Dy concentrations, which can be determined based on the residual stress modulation in the REBa2Cu3O7−δ thin films. In addition, no apparent transition of tensile or compressive stresses is observed in the thin films during the residual stress measurements. This paper provides a useful theoretical guidance for effectively improving the superconductivity of REBa2Cu3O7−δ thin films.

Integration effect of O2‐plasma to an excimer‐laser‐assisted metal organic deposition process for functionalization of photoelectrodes

AbstractTo prevent photocorrosion of a Cu2O photocathode, composition of a TiO2 layer onto the Cu2O is one of the most effective solutions. For crystallization of the TiO2 layer alone without heat‐damage to the underlying Cu2O layer, which is easy to oxidize to CuO, we developed the integration process of O2‐plasma and an excimer‐laser irradiation, that a metal‐organic precursor film is crystalized by irradiation of the excimer‐laser in O2‐plasma. The TiO2 layer could be crystalized with lower oxygen vacancies by the laser irradiation in O2‐plasma compared to that prepared by the irradiation in air. Furthermore, the oxidation of Cu2O to CuO was drastically restricted due to the highly crystalized TiO2 in which oxygen ions were hard to diffuse to the interface of TiO2/Cu2O. The photocorrosion of the obtained film during water reduction reaction was also restricted. This O2‐plasma integrated process is effective for selective crystallization of metal‐oxide films for functionalization of photoelectrodes.

Rapid Epitaxial Growth of GdBa2Cu3O7-σ Films by Dilute Co Doping

The effect of dilute Co doping on the epitaxial growth of GdBCO films was investigated by self-developed fluorine-free polymer-assisted metal-organic deposition (PA-MOD) method. Under the same sintering heat treatment, dilute Co doping dramatically improved the crystallinity, microstructure, and critical current density (Jc) of GdBCO films. High Jc of 4.0 MA/cm2 at 77 K and self-field was obtained in Co-doped film after only sintering for 30 min, which is eight times of the Jc for the undoped film. Also, Co-doped GdBCO film sintered for as short as 20 min still possesses a high Jc of 1.5 MA/cm2, whereas the Jc is 0 for the similarly sintered pure film. These results suggest that dilute Co doping facilitates the epitaxial growth of the high-performance GdBCO film.

A study on the electromagnetic wave shielding property of photosintered copper-silver composite films

Research on photosintering of printable conductive nano-metal ink or metal oxide ink is a very advantageous method in manufacturing flexible devices because it can reduce thermal shock when electrodes are formed on a flexible substrate. In this study, silver (Ag) metal organic deposition (MOD) ink was added to copper (Cu) MOD ink to improve the electromagnetic wave shielding (EMS) property of Cu films sintered by light. Increasing the concentration of Ag up to 2wt% greatly increases the light absorption, electrical conductivity, and EMS effectiveness. Beyond 2 wt%, the composite films showed similar electrical properties to those of Cu-Ag film with 2 wt% Ag. It has been found that by adjusting the light energy, the proper sintering energy of the Cu-Ag film is lowered by the light absorption property of Ag, and the shielding efficiency value can be improved by reducing the thermal damage of the final MOD film.

Development of Flexible RuO<sub>2</sub> Film by Excimer Laser Metal Organic Deposition (ELAMOD)

Development of Flexible RuO<sub>2</sub> Film by Excimer Laser Metal Organic Deposition (ELAMOD)

Growth of YBCO film by chemical solution deposition with an optimization fluorine process

Trifluoroacetate metal organic deposition (TFA-MOD) with low fluorine contents would bring benefits for the environment and the epitaxial growth of YBa2Cu3Oy (YBCO) film. In this paper, a simple and effective method which could tune the fluorine content and improve the performance of YBCO film was reported. YBCO Low-Fluorine/YBCO Fluorine-Free composites were prepared on LaAlO3 single crystal substrate. During the pyrolysis process, the fluorine would diffuse across the interface of YBCO Low-Fluorine/YBCO Fluorine-Free composites. Both the fluorine in the YBCO Low-Fluorine and the carbon in the YBCO Fluorine-Free could be reduced. It could significantly improve the epitaxial growth and performance of YBCO film.

Enhancement of the in-field critical current density of trifluoroacetate metal organic deposition derived (Y0.77Gd0.23)Ba2Cu3Oy films by annealing of CeO2 buffered R-Al2O3 substrates

We investigate the superconducting properties of (Y0.77Gd0.23)Ba2Cu3Oy [(Y,Gd)BCO] films on as-grown and annealed (600 °C–1000 °C) CeO2 buffered R-plane sapphire (R-Al2O3) substrates using trifluoroacetate metal organic deposition (TFA-MOD). The annealing was found to improve the crystallinities of not only the CeO2 buffer layers but also the (Y,Gd)BCO films. Although the anneal had no apparent effect on the pinning centers of the (Y,Gd)BCO films, the in-field Jc of the (Y,Gd)BCO films grown on the CeO2 buffered substrates improved with increasing annealing temperature. The present results are discussed in terms of the crystallinities and Jc values of the (Y,Gd)BCO films.

High-frequency surface acoustic wave devices based on epitaxial Z-LiNbO3 layers on sapphire

Filter market demands push the development of new piezoelectric materials to address the modern telecommunication challenges. Combining composite wafers with an epitaxial piezoelectric layer and a said high velocity and acoustic quality substrate is a promising way to answer those demands. However, the fabrication of high-quality LiNbO3 films with reproducible physical properties is complicated by the difficulty in controlling volatile Li2O incorporation into the film and of measuring its composition. So far, large-scale production of films with physical properties suitable for the targeted applications is not available. In this paper, lithium niobate films with controlled nonstoichiometry were deposited by means of pulsed injection metalorganic vapor phase deposition. We have demonstrated a high acoustical performance for surface acoustic wave devices operating in the frequency range of 3.7 GHz up to 5.3 GHz and based on grown epitaxial Z-axis oriented LiNbO3 films on sapphire. An electromechanical coupling of 8% for the Rayleigh wave at 5.3 GHz was demonstrated experimentally.

Orientations of Al4C3 and Al films grown on GaAs substrates

A method for growth of aluminum epilayers on III-V substrates using metalorganic chemic vapor deposition (MOCVD) processes could be beneficial for optoelectronic and photovoltaic device fabrication. However, deposition from common precursors under standard MOCVD conditions results in polycrystalline Al4C3. Both Al4C3 films grown on GaAs (100) substrates, and those grown on GaAs (111) B substrates, show strong alignment of the rhombohedral [110] for the Al4C3 crystallites with the in-plane GaAs <110> directions. However, by using plasma-enhanced MOCVD at low growth temperatures, elemental Al can be deposited. Al growth by this method on (001), (111) B and (110) GaAs substrates gave textured, polycrystalline films. In all cases, the Al crystallites are primarily oriented with a <110> aligned with an in-plane <110> of the substrate at initial growth stages. These insights may lead towards growth of large-grained or epitaxial Al films.