Metal Organic Decomposition Method Research Articles

Extraordinary enhancement of magneto-optical Faraday rotation angle in Bi-YIG/Pt/glass prepared by metal organic decomposition method

We achieve the extraordinary enhancement of magneto-optical Faraday rotation angle for bismuth-substituted yttrium iron garnet (Bi-YIG) using the metal-organic decomposition method, by introducing a Pt underlayer. The Faraday rotation angle reaches -25°/μm for the sample with a Pt thickness of 45 nm, which is 5 times higher than that of a bare thin film, setting a new record value for chemically synthesized Bi-YIG films. Through X-ray diffractometer, vibrating sample magnetometer, and energy dispersive X-ray spectroscopy analyses, we found that this enhancement is attributed to improved crystallinity, saturation magnetization, and the formation of a PtBi alloy phase, facilitated by Pt acting as an absorbing layer of Bi. We propose that the Bi-YIG/Pt film structure, with an optimum thickness of Pt underlayer, shows great promise for applications in various magneto-optical devices that require high detection sensitivity for small signals.

Spin thermoelectric and spin transport in YIG films fabricated by chemical method

Spin transport in heterojunctions between magnetic insulators and heavy metals has garnered significant attention due to its potential in spintronics applications. In this study, we employed the metal-organic decomposition (MOD) method to fabricate high-quality yttrium iron garnet (Y3Fe5O12-YIG) films on (111)-oriented gadolinium gallium iron garnet (Gd3Ga5O12-GGG) substrate. We conducted a thorough characterization of the crystallinity, surface morphology, and magnetic properties of the YIG films at various thicknesses. The obtained samples exhibited smooth surfaces with roughness mean-square (RMS) below 0.6 nm. Epitaxial growth was maintained for films up to 116 nm in thickness but deteriorated beyond that. The magnetic anisotropy demonstrated an easy axis in the in-plane direction, accompanied by a low coercivity of 4.8 ± 0.4 Oe. The spin Seebeck effect voltage measurement shows the highest signal for 366 nm thick film and is reduced if the thickness increases. Furthermore, we investigated spin transport across the YIG/Pt interface using spin Hall magnetoresistance. The average spin-mixing conductance (Gr) was determined to be 5.79 ± 0.54 × 1014 Ω−1m−2, a value comparable to those reported in previous studies.

Magneto-Conductive and Magnetic Properties in La<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>MnO<sub>3 </sub>Thin Films on a-SiO<sub>2</sub> Substrates Produced by Metal Organic Decomposition Method

We have studied magneto-conductive and magnetic properties of La1-xSrxMnO3 (LSMO) thin films on a-SiO2 substrates produced by the metal organic decomposition (MOD) method. LSMO thin films for x = 0, 0.15 and 0.3 have been produced in a pure O2 gas atmosphere. Although LaMnO3 (LMO) single crystal is an antiferromagnetic insulator (AFI), LMO thin films we have produced show ferromagnetic metal (FM) properties for suitable heat treatment conditions. We consider that the excess of O2- ions in LMO thin films produced in a pure O2 gas atmosphere induces the strong hole self-doping into those and the LMO thin films change from AFI to FM. Whereas, the ordinary hole doping is also occurred in LSMO thin films at x > 0. Thus, the carrier doping for LSMO thin films at x > 0 is caused by the hole self-doping by O2- ions and the ordinary hole doping by the replacement of La3+ ions by Sr2+ ones. To investigate the crystallographic and surface structures of the LSMO thin films, X-ray diffraction and SEM measurements have been performed, respectively. From the X-ray diffraction measurement, we have found that all LSMO thin films have perovskite structure and are polycrystalline. From the SEM measurement, we have seen that the LSMO thin films are formed of the aggregation of LSMO fine particles. Electrical resistivities (ERs) and magneto-resistivity (MR) ratios of the LSMO thin films have been measured on the temperature dependence (4K-300K). From MR ratio measurements, the coercive forces of them have been obtained as a function of temperature, and the Curie temperatures have been estimated from the temperature dependences of the coercive forces. We have discussed the origin of the magneto-conductive and magnetic properties of LSMO thin films.

Fabrication and characterization of zirconium oxide coating on tubular steel by metal organic decomposition

In fusion reactor blankets, multifunctional ceramic coatings fabricated on structural materials have been investigated for tritium permeation reduction, electrical insulation, and corrosion protection. However, it has been challenging to manufacture a homogeneous coating on the complicated components in the blanket breeder, such as ducts. In terms of sustainable development, it is crucial to establish a ceramic coating technique on the inner walls of fuel pipes in liquid blanket systems. In this study, we applied the metal organic decomposition method to fabricate zirconium oxide coatings on 316L austenitic stainless steel tubes and characterized their properties as liquid tritium breeding pipes. Homogeneous zirconium oxide coatings with a thickness of 395 ± 12 nm have formed on the inner walls of SS316L tubes. The compatibility of the coated tubes with liquid lithium-lead was examined under static and flowing conditions at 550–600 °C for prolonged exposure of up to 2000 h. Under static conditions, ZrO2 coatings demonstrated exceptional compatibility with the liquid Li-Pb as they protected structural material from corrosion. At a flow rate of 0.16 m/s, the coatings were partly delaminated due to different thermal expansion coefficients of the coating and substrate and acceleration under a dynamic system. The coating thickness increased up to 650 ± 26 nm after exposure for 2000 h, which indicated ZrO2 coatings reacted with Li-Pb to form corrosion products. Besides, ZrO2 coatings achieved the insulating requirements of magnetohydrodynamic insulators as their electrical resistivities were on the order of 104–106 Ω m at the temperature range of 250–550 °C.

Fabrication of BixY3-xFe5O12 thin films by thermal decomposition of metal oleates

Metal organic decomposition (MOD) for the metal oxides thin films fabrication has been used in various studies over the past 30 years. MOD is a simple and inexpensive method for manufacturing optical grade polycrystalline thin films, including bismuth-substituted yttrium iron garnet. We present a variant of the previously described MOD method and discuss a chemical route for fabricating thin porous oxide films with a thicknesses of more than 100 nm, which non-epitaxially crystallized on fused silica substrates into BixY3-xFe5O12 layers (x = 0.5 and 1.5). Studies of the structural and magneto-optical properties of the layers show that the garnet layers crystallized under optimal conditions are characterized by high values of the specific Faraday rotation. Importantly, crystallization can be done locally by laser irradiation, and wet etching makes possible to remove non-crystallized areas, thus extending microfabrication capabilities.

Large recoverable energy storage density and efficiency in PbZrO3-xSrTiO3 thin films with polymorphic nanodomains

PbZrO3-xSrTiO3 solid solution thin films were designed and fabricated by a metal organic decomposition method, and their structural, ferroelectric, and energy storage characteristics were investigated systematically. It is found that the incorporation of SrTiO3 not only gradually transforms PbZrO3 from antiferroelectrics to relaxor ferroelectrics but also obviously increases its breakdown strength. Large ferroelectric polarization and electric-field-dependent effective permittivity are obtained in the PbZrO3-0.4SrTiO3 thin film due to the coexistence of rhombohedral (R), tetragonal (T), and orthorhombic (O) polymorphic nanodomains and polar clusters, which results in simultaneously improved recoverable energy storage density (Wrec ∼73.7 J/cm3) and efficiency (η ∼72%). Moreover, excellent temperature stability (the variations of Wrec and η are both less than 5% as temperature increases from 243 to 393 K) and distinguished fatigue endurance (the variations of Wrec and η are both less than 1% after 108 cycles) are realized in a PbZrO3-0.4SrTiO3 thin film. This study provides a feasible alternative method for designing energy storage materials based on antiferroelectrics.

BaMO3 (M = Zr, Hf) Doped REBCO Tapes Fabricated by Fluorine-Free MOD

Using a low-cost fluorine-free metal organic decomposition (FF-MOD) method, REBCO films with BaMO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BMO, M = Zr, Hf) artificial pinning centers were fabricated. When M elements are conventionally added to the solution, the size of BMO formation depends on the growth conditions. But by adding preformed BMO nanoparticles, the size can be maintained on the nanometer order, meaning the nanoparticles act as effective pinning centers at low temperatures and magnetic fields. Adopting a polycrystallization sintering process enables the BaCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> to decompose completely and polycrystalline REBCO films to form prior to REBCO orientation. After final sintering, REBCO orientation can be achieved over a wide temperature range even with the addition of BMO nanoparticles. By utilizing preformed BMO nanoparticles and a polycrystallization sintering process, BMO doped GdBCO over 100 m-long tapes which have a thickness of more than 3 μm can be achieved. This is the first report of 120-meter-long artificial pinned REBCO tapes with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> exceeding 200 A/4 mm width at 77 K, self-field made by the FF-MOD method.

Insight into the Key Restriction of BiVO4 Photoanodes Prepared by Pyrolysis Method for Scalable Preparation.

Bismuth Vanadate (BiVO4 ) photoanode has been popularly investigated for promising solar water oxidation, but its intrinsic performance has been greatly retarded by the direct pyrolysis method. Here we insight the key restriction of BiVO4 prepared by metal-organic decomposition (MOD) method. It is found that the evaporation of vanadium during the pyrolysis tends to cause a substantial phase impurity, and the unexpected few tetragonal phase inhibits the charge separation evidently. Consequently, suitably excessive vanadium precursor was adopted to eliminate the phase impurity, based on which the obtained intrinsic BiVO4 photoanode could exhibit photocurrent density of 4.2 mA cm-2 at 1.23 VRHE under AM 1.5 G irradiation, as comparable to the one fabricated by the currently popular two-step electrodeposition method. Furthermore, the excellent performance can be maintained on the enlarged photoanode (25 cm2 ), demonstrating the advantage of MOD method in scalable preparation. Our work provides new insight and highlights the glorious future of MOD method for the design of scale-up efficient BiVO4 photoanode.

Insight into the Key Restriction of BiVO4 Photoanodes Prepared by Pyrolysis Method for Scalable Preparation

AbstractBismuth Vanadate (BiVO4) photoanode has been popularly investigated for promising solar water oxidation, but its intrinsic performance has been greatly retarded by the direct pyrolysis method. Here we insight the key restriction of BiVO4 prepared by metal–organic decomposition (MOD) method. It is found that the evaporation of vanadium during the pyrolysis tends to cause a substantial phase impurity, and the unexpected few tetragonal phase inhibits the charge separation evidently. Consequently, suitably excessive vanadium precursor was adopted to eliminate the phase impurity, based on which the obtained intrinsic BiVO4 photoanode could exhibit photocurrent density of 4.2 mA cm−2 at 1.23 VRHE under AM 1.5 G irradiation, as comparable to the one fabricated by the currently popular two‐step electrodeposition method. Furthermore, the excellent performance can be maintained on the enlarged photoanode (25 cm2), demonstrating the advantage of MOD method in scalable preparation. Our work provides new insight and highlights the glorious future of MOD method for the design of scale‐up efficient BiVO4 photoanode.

Praseodymium-dopant effect on bismuth-substituted yttrium iron garnet films on fused silica glass substrate at the 1310 and 1550-nm wavelengths

The optical and magneto-optic (MO) properties of the praseodymium (Pr)-dopant effect on bismuth-substituted yttrium iron garnet (Bi:YIG) films coated on fused silica glass substrates by using the metal-organic-decomposition (MOD) method with chemical solutions were investigated at the 1310 and 1550-nm wavelength regions. The maximum Faraday rotation angle of the Pr-codoped Bi:YIG (Pr,By:YIG) film was observed to be 0.09 and 0.046 deg/μm at the wavelengths of 1310 and 1550 nm, respectively, when the film was annealed at a temperature of 750 °C, while those of the plain Bi:YIG film were 0.059 and 0.039 deg/μm. More than 50% improvement in the Faraday rotation value of the Pr,Bi:YIG film was observed compared to that of the Bi:YIG film at the 1310 nm wavelength. The absorption coefficient of the Pr,Bi:YIG film was comparable to that of the Bi:YIG film. Therefore, the Pr,Bi:YIG film prepared with the MOD method is potentially useful for MO applications such as optical isolators and circulators.

Effect of annealing temperature and thickness on the structural and optical properties of strontium bismuth niobate films

Strontium Bismuth Niobate (SBN) thin films were prepared by metal organic decomposition method. The effects of post deposition annealing temperature (500–900 °C) and thickness (200–650 nm) on the structural and optical properties have been discussed. X-ray diffraction studies indicate the formation of single phase structure at annealing temperature of 800°C. The crystallinity of the samples improved with the increase in film thickness (200–500 nm), however, structural changes were observed beyond film thickness 500 nm. The changes in surface morphology of the films have been discussed as a function of annealing temperature and thickness. Although well-defined Raman spectra were obtained at higher annealing temperature (≥700 °C) for low thickness film, low frequency Raman modes were observed for higher thickness film (≥500 nm). The optical transmittance of the film decreases with increase in thickness from 200 to 650 nm. The energy band gap and refractive index have been estimated as a function of annealing temperature and film thickness. The band gap values decreased from 4.38 to 3.88 eV with the increase in film thickness. The correlation between structural and optical properties has been done in order to optimize annealing temperature and film thickness at 800 °C/ 500 nm.

Spin Hall magnetoresistance and the effect of post-annealing temperature in the MOD-grown HoIG

We present the fabrication of ultrathin Ho3Fe5O12 (HoIG) films on 111- oriented-Gd3Ga5O12 (GGG) via the metal-organic decomposition (MOD) method followed by a sequence annealing process. We characterized the crystal structure, surface morphology, and magnetic properties to study the effect of annealing temperature on the quality of MOD-grown HoIG films. For temperatures higher than 800 ⁰C, we observe the infiltration of Iron (Fe) from the HoIG film into the GGG substrate. In particular, the Fe-diffusion is significantly enhanced for a 1000 ⁰C-annealed sample of which crystal structure and magnetic properties are also affected. For temperatures lower than 800 ⁰C, on the other hand, the smooth surface and strong crystallinity cannot be guaranteed. This suggests that an annealing temperature of 800 ⁰C is the optimal condition for the MOD-grown HoIG film. The quality of the sample is further confirmed by measuring the spin Hall magnetoresistance (SMR) of HoIG/Pt, in which we found the unconventional angular dependence and comparable spin mixing conductance similar to the previous reports in other single crystalline IGs.

The FMR line width and the structure in YIG films deposited by MOD on silicon (1 0 0)

In this work, yttrium-iron garnet (YIG) films deposited on silicon subtract were studied by ferromagnetic resonance (FMR). The samples were prepared by using the Metal-Organic Decomposition (MOD) method on two different thermal treatments (750 °C and 850 °C). The X-ray diffraction suggested the single phase of YIG while atomic force microscopy and scanning electron microscopy reveled film roughness, Rq < 0.2 nm. The FMR measurements showed very different linewidth of 139 Oe for the sample obtained at 750 °C and sample at 850 °C had a smaller linewidth of 93 Oe. The difference was mainly attributed to the different structural ordering of the two samples from the heat treatment at different temperatures.

NiFePB-modified ZnO/BiVO4 photoanode for PEC water oxidation.

Photoelectrochemical (PEC) water splitting has been recognized as the most promising approach for directly converting solar energy into chemical energy, and substantial efforts have been made to develop a highly efficient and low-cost photoanode for enhancement of PEC water splitting efficiency due to sluggish water oxidation reaction kinetics. A ternary NiFePB-modified ZnO/BiVO4 heterojunction photoanode was simply assembled by low-temperature hydrothermal, metal-organic decomposition and electrodeposition methods to improve the water splitting efficiency; its photocurrent density for water oxidation reached 1.66 mA cm-2 at 1.23 V (vs. RHE); in comparison, that of ZnO is only 0.4 mA cm-2. The onset potential manifests a cathodic shift of ∼283 mV compared to ZnO. The IPCE and the ABPE respectively are 3.1 and 6.4 times those of ZnO, respectively. This improvement is ascribed to the efficient separation of photogenerated electrons and holes by the formation of a heterojunction between ZnO and BiVO4 and the enhancement in the oxygen evolution reaction kinetics by the decoration of the co-catalyst NiFePB as a hole acceptor.

Preparation and characterization of YMnO3 thin films by metal–organic decomposition

Hexagonal rare-earth manganese oxide YMnO3 thin films were prepared on yttria-stabilized zirconia (111) substrates by metal organic decomposition method. The crystallinity and morphology of YMnO3 thin films crystallized at various temperatures were examined by X-ray diffraction and atomic force microscopy measurements, respectively. Single phase YMnO3 was obtained for the sample prepared by annealing temperatures of 950 °C. AFM analysis revealed that a smooth surface with a roughness of 0.15 nm was achieved for YMnO3 thin film annealed at 950 °C and 1000 °C, while three-dimensional growth for other samples prepared at 750–900 °C, 1050 °C, and 1100 °C. A narrow band at 1.6 eV and a broad band at 5 eV due to electronic transitions in the manganese and oxygen bands were observed in an absorption spectrum.

Magneto-optical property and magnetic anisotropy of (100) oriented R0.5Bi2.5Fe5O12 (R = Eu, Sm, and Pr) thin films prepared by metal–organic decomposition

Bi-substituted rare-earth iron garnets, R3−xBixFe5O12 (Bi:RIG), where R represents one of the rare-earth elements, exhibit the excellent magneto-optical (MO) properties that increase with Bi content x. In addition, magnetic properties of Bi:RIGs, such as the magnetization, the magnetic anisotropy, and the magnetostriction, could be controlled by choosing rare-earth elements. In this paper, we report on R0.5Bi2.5Fe5O12 (Bi2.5:RIG, R = Pr, Sm, and Eu) thin films on Gd3Ga5O12 (GGG) (100) single crystal substrates prepared by the metal–organic decomposition method. XRD analysis reveals that Bi2.5:RIG thin films are grown along the same orientation with GGG substrates, and their lattice constants are dependent on the ionic radii of the rare-earth ions. MO measurements show that Faraday spectra of the Bi2.5:RIG thin films have a typical spectral structure observed for Bi:RIGs. The magnetic anisotropy constants, the uniaxial magnetic anisotropy energy Ku, and the magnetocrystalline anisotropy energy K1 of Bi2.5:RIG (R = Y, Pr, Nd, Sm, and Eu) thin films are investigated by using the ferromagnetic resonance measurement.

Thickness dependence of spin Seebeck resistivity in polycrystalline YIG films grown by metal organic decomposition method

In this work, we investigated the dependence of spin Seebeck effect (SSE) voltages on the thickness of yttrium iron garnet (Y3Fe5O12-YIG) thin films grown on a silicon (Si) substrate fabricated by a metal-organic decomposition (MOD) method. The thickness of films was controlled by repeated spin coating and annealing cycles. Based on grazing incidence X-ray diffraction measurements, the YIG thin films displayed high crystallinity without secondary peaks, despite the increase in thickness. Scanning electron microscopy revealed uniform, highly dense films for samples having a thickness in the range of 37–260 nm. Magnetic hysteresis loops showed similar coercivities of <36 Oe for all samples, confirming the high quality of the YIG films, regardless of mismatch between the lattice constants of YIG and the substrate. Spin Seebeck resistivity results revealed a strong dependence on the thickness of the samples and the local maxima for 138-nm-thick YIG. This was attributed to the effect of the magnon energy relaxation length (ξL), which is shorter in comparison to that of a single-crystal YIG film grown on gadolinium gallium garnet. In this study, facile fabrication of hundreds of nanometers-thick YIG films on a Si substrate was achieved, for applications involving thermoelectric energy harvesting.

Optical and magneto-optical properties of bismuth-substituted neodymium iron gallium garnet films on glass substrates at the 1310-nm and 1550-nm wavelengths

We describe measured results of optical and magneto-optical (MO) properties of bismuth-substituted neodymium iron gallium garnet (Bi1Nd2Fe4Ga1O12, Bi1:NIGG) films prepared by spin coating on glass substrates and crystallized by metal–organic decomposition (MOD) method in the near-infrared (NIR) wavelengths of 1310 nm and 1550 nm. The optical constants of the Bi1:NIGG films were determined with a spectrophotometer measurement. The measured refractive index and absorption coefficient were about 1.835 and 55.8 cm−1, respectively, at the 1310 nm wavelength and about 1.837 and 29.8 cm−1 at the 1550 nm wavelength. The MO properties of the films were determined by measuring the Faraday rotation in the saturated magnetization region. The measured maximum Faraday rotation of the Bi1:NIGG film of about 1055-nm thickness was 0.032 °/μm and 0.016 °/μm at 1310-nm and 1550-nm wavelengths, respectively. The corresponding Figure-of-Merits (FoMs) were 5.64 deg/dB and 5.22 deg/dB at each wavelength. Our measured result indicates that the Bi1:NIGG films prepared by the MOD method are useful for integrated optical isolator and MO sensor applications because of relatively good optical transparency and MO characteristics.

Effects of Ta, Nb, Ba, and Sb concentration on structural, electrical, and optical properties of SnO2 thin films prepared by metal organic decomposition using spin coating

Ta-, Nb-, Ba-, and Sb-doped SnO2 thin films were prepared by the metal organic decomposition (MOD) method using spin coating. The effects of dopant concentration on the structural, electrical, and optical properties were investigated. The growth of polycrystalline films with the tetragonal rutile structure was confirmed by X-ray diffraction and atomic force microscopy measurements. The resistivity of Ta-, Nb- and Sb-doped SnO2 samples decreased to ∼10−3 Ωcm for dopant concentrations of around 1.5–3.0 at.%. The lowest resistivities were obtained for Ta- and Sb-doped SnO2 samples. On the other hand, no decrease in resistivity was observed for Ba-doped SnO2 samples. The band gap energy of Ta-, Nb-, Ba-, and Sb-doped SnO2 samples appeared to be larger than for those prepared by other methods. It was suggested that the structural deterioration may be related to the increase in the band gap energy for MOD prepared samples in addition to the Burstein-Moss effect.

Highly sensitive and stable H2 gas sensor based on p-PdO-n-WO3-heterostructure-homogeneously-dispersing thin film

The film-based gas sensor owning high compatibility with semiconductor device fabrication, plays an important role in the miniaturization and integration of the devices. Here, simple metal organic decomposition method and calcining procedure were used to prepare dense WO3 thin film with PdO nanoparticles being homogeneously dispersed. After painting the silver paste on its surface as electrodes, the H2 gas sensor was fabricated. At the optimal operating temperature of 160 °C, with response values (Ra/Rg) of 1.2 & 45.1 and response time of 38 s & 4 s, towards 500 ppb and 100 ppm H2, respectively, the sensor presents high sensitivity and low detection limit together. It is rare to report the H2 gas sensor based on dense semiconductor film with such low detection limit. Towards 500 ppb and 100 ppm H2, it still shows the same response values more than half a year later, which proves its stability. A good linear behaviour between the response and relative humidity is observed too. The chief cause of the better performance of the sensor may be the homogeneous and optimal distribution of the p-type PdO nanoparticles in n-type WO3 film, which is the character of this structure. In addition, the repeatability of the preparing process is very well too. All the better performances suggest that the H2 sensor based on this structure has a huge potential in practical application.