Metalorganic Decomposition Technique Research Articles

Preparation of (La1 − xSrx)MnO3 − δ thin films on Si (100) substrates by a metal-organic decomposition method for smart radiation devices

(La1−xSrx)MnO3−δ (LSMO) thin films were prepared on Si(100) substrates using a metal-organic decomposition (MOD) technique for smart radiation devices used for thermal control in spacecraft. The 6wt% concentration MOD precursor solutions were spin-coated on Si substrates. The coated films were dried at 90°C and pyrolytically decomposed at 530°C. Finally, they were annealed in air at 750°C to obtain dense, polycrystalline, and single-phase perovskite LSMO films. A ferromagnetic-paramagnetic phase transition was observed close to room temperature in a LSMO film. The thermal emittance of the film was changed as a result of this phase transition. The phase transition temperature increased with an increasing Sr ratio at the A-site of the LSMO and decreased after annealing under a reduced atmosphere. Based on this result, we propose that the temperature range where the thermal emittance is widely variable can be finely tuned on demand with post-annealing.

Study of molar ratio on the characteristics of metal–organic decomposed LaxCe1−xOz film as a metal reactive oxide on Si substrate

A metal–organic decomposition technique was employed in this study for the preparation of a solution precursor using different molar ratios of lanthanum (La) to cerium (Ce), which was spin-coated on an n-type Si substrate. Post-deposition annealing was subsequently performed at 1000°C for 15min in argon on the samples to transform the precursor into lanthanum cerium oxide (LaxCe1−xOz) film. This work correlated the influence of decreasing content of La3+ in the LaxCe1−xOz film with formation of oxygen vacancies. Generation of higher amounts of oxygen vacancies in LaxCe1−xOz has evoked an interest in the study of LaxCe1−xOz as a metal reactive oxide on Si substrate for oxygen gas sensing. These oxygen vacancies would serve as active sites for capturing oxygen ions, which were formed as a result of chemisorption of oxygen atoms originating from oxygen gas. The response of oxygen gas sensing for the fabricated Al/LaxCe1−xOz/Si metal–oxide–semiconductor structures was characterized and discussed.

Magneto-optical effect and ferromagnetic resonance of Bi–Fe garnet for high frequency electromagnetic sensor

In order to develop a new probe sensor for high frequency electromagnetic field generated around integrated electric circuits, we have synthesized thermally nonequilibrium Bi3Fe5O12 (BIG) and Bi3Fe5−xGaxO12 [(BIGG), x = 0.2, 0.5, 1.0] films from metalorganic decomposition technique. The BIG materials are famous for the largest magneto-optical (MO) effect in visible light region. Ga substitutions are expected to increase the sensitivity of the MO effect to magnetic fields. For the preparation of the films, metalorganic solutions were spin coated on the garnet single-crystal substrates and then were annealed in the furnace. The optimized annealing temperature for BIG and BIGG is determined to be around 480 °C. The BIG film showed the largest Faraday rotation of approximately 6°/μm at 630 nm. The Ga substitution increases the change ratio of the Faraday rotation to the magnetic field from approximately 5 to 11×10−3 deg/μm Oe. The half width of the ferromagnetic resonance (FMR) line shape of the BIG was appro...

Ferroelectric SrBi2Ta2O9 Thin Film Studied by Micro-Raman Scattering and Atomic Force Microscopy

Ferroelectric SrBi2Ta2O9 thin films were prepared by metal-organic decomposition technique on Si wafers. The thickness dependence of the films was studied by micro-Raman scattering and atomic force microscopy (AFM). From the AFM observation, it is found that films were constructed of c-axis-oriented grains. The low frequency component of the Raman spectra of the films decreases as the temperature increases. The spectral analysis of the low frequency component has been carried out by using a damped harmonic-oscillator model and a relaxational model. The relaxation time has the similar value of that reported in KDP. It is suggested the physical origin of the low frequency component may be polarization fluctuation.

Effect of Annealing on Ferroelectric Properties of Lanthanum Modified Lead Zirconate Titanate Thin Films

Thin films of lanthanum modified lead zirconate titanate with chemical formula (Pb0.95La0.05Zr0.54Ti0.46O3) were prepared using spin coating method. The sol for the PLZT was prepared in house by metal organic decomposition (MOD) technique. The prepared films were annealed in the temperature range of 550–750°C in a rapid annealing furnace in flowing oxygen to promote crystallinity in the films. Effect of post deposition annealing temperatures on the structure/morphology and ferroelectric properties of the films were examined using X-ray diffraction, atomic force microscopy and ferroelectric tester. Parameters were optimized for obtaining films with excellent ferroelectric properties and low leakage currents. A high value of polarization ∼ 72μC/cm2 coupled with a minimum leakage current density of 10−8A/cm2 was obtained from films annealed at temperature of 750°C. The results indicate that choice of proper annealing process is vital to control the structure and morphology which are important parameters to achieve good ferroelectric properties in PLZT films. These films are being used to study the photovoltaic response from such material for their potential use in ferroelectric photovoltaic devices.

Cobalt-phosphate (Co-Pi) catalyst modified Mo-doped BiVO4 photoelectrodes for solar water oxidation

A cobalt-phosphate based oxygen evolution catalyst (Co-Pi OEC) was electrochemically deposited onto the surface of a porous bismuth vanadate electrode doped with 2 atom% Mo (BiV0.98Mo0.02O4). The porous BiV0.98Mo0.02O4electrode was prepared using a surfactant assisted metal–organic decomposition technique at 500 °C. The comparison of the photocurrent–voltage characteristics of the BiV0.98Mo0.02O4electrodes with and without the presence of Co-Pi catalyst demonstrated that the Co-Pi catalyst enhanced the anodic photocurrent of the BiV0.98Mo0.02O4electrode with its effect more pronounced at lower potentials. A stable photocurrrent density of 1.0 mA cm−2 at 1.0 V vs.Ag/AgCl was achieved under standard AM 1.5 illumination using 0.5M Na2SO4 aqueous solution in phosphate buffer at pH7. Relative to the BiV0.98Mo0.02O4electrode, a sustained enhancement, nearly doubled photocurrent density was observed at 1.0 V vs.Ag/AgCl for Co-Pi/BiV0.98Mo0.02O4 composite photoelectrode. Significant performance gains are obtained on BiV0.98Mo0.02O4electrodes upon modification with Co-Pi water oxidation catalyst.

Chemical Reaction and Crystalline Procedure of Bismuth Titanate Nanoparticles Derived by Metalorganic Decomposition Technique

The homogeneous bismuth titanate single-phase nanoscaled ceramic powders have been prepared by means of metalorganic decomposition. The thermal decomposition/oxidation of the preheated precursor, as investigated by differential thermalgravimetric analysis, X-ray powder diffraction, and environment scanning electron microscope, lead to the formation of a well-defined orthorhombic bismuth titanate compound. Formation of the layered perovskite-like bismuth titanate occurs via intermediates with sequential changes in the coordination polyhedron of bismuth. The chemical reactions of precursor powder in heat treatment process have been investigated further by Raman and Fourier transform infrared spectra, and the reaction mechanism was tentatively proposed thereafter.

FERROELECTRIC PROPERTIES AND FATIGUE BEHAVIOR OF (Pb0.5Ca0.5)TiO3 THIN FILM

ABSTRACT The ferroelectric polarization switching and fatigue behavior of (Pb, Ca)TiO3 thin films with a high calcium concentration of 50% deposited by metal-organic decomposition technique have been studied. The as-grown (Pb0.5 Ca0.5)TiO3 thin films exhibit good ferroelectric properties with spontaneous polarization Ps = 12.3 , remanent polarization Pr = 6.3 and coercive field Ec = 137 kV/cm. It is found that at a high-applied voltage and switching time, charge injection influences the polarization switching behavior of the film. The film also exhibits good fatigue endurance up to ∼107 switching cycles even without the oxide electrodes.

Low temperature preparation of ferroelectric bismuth titanate thin films

The low temperature metal organic decomposition techniques of ferroelectric bismuth titanate (BIT) thin films were investigated. BIT was found to be crystallized by rapid thermal processing at 450 °C. The stoichiometric Bi4Ti3O12 sample exhibited (117) orientation, while the Bi4.8Ti3O13.2 sample, with 20% excess bismuth, possessed a/b axes orientation with (117) component. Pt/Bi4.8Ti3O13.2/Pt ferroelectric capacitors were fabricated with temperature confined below 450 °C. The saturated 2Pr value was 31.1 μC/cm2. Such method is valuable for ferroelectric memories at 65 nm technology node and beyond because low temperature processes are required for the stability of interconnect material nickel silicide.

Preparation and characterization of BiVO 4 film electrode and investigation of its photoelectrocatalytic (PEC) ability under visible light

BiVO 4 film coated on F-doped SnO 2 (FTO) glass was successfully fabricated by modified metalorganic decomposition (MOD) technique. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images showed that the film was composed of grains with 200–300 nm in size and the grains were composed of particles, which were about 10 nm in size. Diffused reflectance spectroscopy (DRS) revealed that the absorption performance of the BiVO 4 film was intense in visible light region and the band gap was 2.43 eV. The analysis of X-ray diffractometry (XRD) and Raman spectra identified to the monoclinic type BiVO 4. Photoelectrochemical measurements indicated the photocurrent densities of BiVO 4 films had an elevation with the increase of film thickness from 0.23 to 1.04 μm due to enhanced amount of absorption of the incident photons. The removal rate of phenol in photoelectrocatalytic (PEC) process by the BiVO 4 film electrode under visible light (>400 nm) was 27.1 times that in photocatalytic (PC) process. The prominent enhancement was induced by the promoted separation of photogenerated electron–hole pairs. Furthermore, the BiVO 4 film electrode coated on FTO glass showed good stability in the PEC process.

Improved dielectric properties of (1 1 0)-preferred (Pb, La) (Zr, Sn, Ti)O 3 antiferroelectric thin films on metalorganic decomposition-derived LaNiO 3 buffer layer

In the present investigation, LaNiO 3 (LNO) perovskite thin films were firstly deposited on Pt(1 1 1)/Ti/SiO 2/Si substrates through the metalorganic decomposition technique, then (Pb 0.97La 0.02)(Zr 0.87Sn 0.10Ti 0.03)O 3 (PLZST 2/87/10/3) antiferroelectric thin films were subsequently grown on Pt(1 1 1)/Ti/SiO 2/Si and LNO-buffered Pt(1 1 1)/Ti/SiO 2/Si substrates via the sol–gel method, respectively. The effect of LNO buffer layer on the microstructure and electrical properties of PLZST 2/87/10/3 antiferroelectric thin films were studied in detail. XRD patterns and SEM pictures indicated that PLZST 2/87/10/3 antiferroelectric thin films grown on LNO buffer layer displayed a (1 1 0)-preferred orientation and had a uniform surface structure. The results of dielectric measurements illustrated that PLZST 2/87/10/3 antiferroelectric thin films on LNO-buffered Pt(1 1 1)/Ti/SiO 2/Si substrates had improved dielectric properties.

Temperature dependence of oriented growth of Pb[Yb 1/2Nb 1/2]O 3–PbTiO 3 thin films deposited on LNO/Si substrates

(1 − x)Pb[Yb 1/2Nb 1/2]O 3– xPbTiO 3 (PYbN–PT, x = 0.5) (001) oriented thin films were deposited onto LaNiO3 (LNO)/Si (001) substrates by sol–gel processing. The crystallographic texture of the films was controlled by the annealing temperature and heating rate. Highly (001) oriented LNO thin films were prepared by a simple metal organic decomposition technique, and the samples were annealed at 700 °C and 750 °C using a rapid thermal annealing process and furnace, respectively. X-ray diffraction analysis revealed that the films of PYbN-PT were highly (001) oriented along LNO/Si substrates. The degree of PYbN-PT orientation is dependent on the heating rate and annealing temperature. Annealing heating rate of 10 °C/s and high annealing temperature near 750 °C produce the greatest degree of (001) orientation, which gives rise to improved dielectric properties.

Improved dielectric properties of (Pb,Ca)TiO 3 thin films prepared by metal-organic decomposition method

(Pb,Ca)TiO 3 (PCT) thin films have been deposited on Pt/Ti/SiO 2/Si substrate by metal-organic decomposition (MOD) technique. The film processing parameters such as drying and annealing temperatures have been optimized to obtain good-quality PCT films. Compositional analysis of the film has been studied by X-ray photoelectron spectroscopy (XPS). The effect of the annealing temperature on the crystalline structure, microstructure and electrical properties have been investigated by X-ray diffraction, atomic force microscopy (AFM) and impedance analyzer, respectively. Amorphous PCT films form at 350 °C and crystallize in the perovskite phase following the isothermal annealing at ⩾650 °C for 3 h in oxygen ambient. Typical tetragonal structure of the PCT film is evidenced from X-ray diffraction pattern. The grain size in the PCT films increases with an increase in annealing temperature. Significant improvement in the dielectric constant value is observed as compared to other reported work on PCT films. The observed dielectric constant and dissipation factor at 100 kHz for 650 °C annealed PCT films are 308 and 0.015, respectively. The correlation of the film microstructural features and electrical behaviors is described.

Synthesis of ultra-fine porous tin oxide fibres and its process characterization

Porous rutile-structured SnO2 fibres, with their length of several millimetres, diameter from 100 nm to40 µm and potentials for sensor applications, were synthesized froma precursor solution of poly(ethylene oxide) (PEO), chloroform(CHCl3) anddimethyldineodecanoate tin (C22H44O4Sn) using electrospinning and metal–organic decomposition techniques. Fourier-transforminfrared spectroscopy, thermogravimetric and differential thermal analysis and x-ray diffractionwere used to characterize the synthesized fibres so as to reveal the series of physical andchemical changes occurring from the starting chemicals to the final product of ultra-fineSnO2 fibres: thesolvent CHCl3 evaporates during the electrospinning; the organic groups in PEO andC22H44O4Sn decompose, with Sn–Cbond in C22H44O4Sn replaced bySn–O between 220 and 300 °C, and the atomic arrangement transforms into the genesis of a rutile-type lattice between 300 and380 °C; theincipient lattice finally develops into the rutile structure during heat treatment at higher temperaturesup to 600 °C.

Ion implantation and ion beam analysis of MOD deposited oxide films

Dilute magnetic oxide semiconductors are new materials that are semiconducting oxides substituted with magnetic or other transition elements. Several oxide films such as TiO2 and ZnO have gained important in recent years in spintronic applications and for photocatalytic applications. This paper deals with oxide films of TiO2 and V2O5 deposited by metal organic decomposition (MOD) technique. The method involves deposition by spin coating from specially selected metal organic precursors and subsequent annealing. The thickness, composition, orientation of the film on a single crystal substrates (sapphire, Si, MgO) and residual C concentration were all measured by ion beam analysis Rutherford backscattering spectrometry in channeling mode (RBS/c) and nuclear reaction analysis (NRA). X-ray diffraction and Raman spectroscopy were used for analysis of the structure of the oxide films. Stoichiometric oxide films of appropriate thickness were subsequently doped with elements such as Fe, Co and V either using a suitable metal organic solution or by ion implantation. The effect of doping on optical and photocatalytic properties are discussed and compared for solution doped films with those doped using ion implantation.

비휘발성 메모리 소자응용을 위한 Eu 첨가량에 따른 BET 박막의 강유전 특성

The effect of Eu contents on the ferroelectric properties of <TEX>$Bi_{4-x}Eu_xTi_3 O_{12}$</TEX> (BET) thin films has been investigated. Bismuth Europium titanate thin films with a Eu contents were prepared on the <TEX>$Pt/Ti/SiO_2/Si$</TEX> substrate by metal-organic decomposition technique. The structure and the morphology of the films were analyzed using X-ray diffraction (XRD) and field emission scanning microscopy (FE-SEM), respectively. From the XRD analysis, it was found that BET thin films have polycrystalline structure, and the layered-perovskite phase is obtained when the Eu contents exceeds 0.2 (x > 0.2). Also, the ferroelectric characteristics of the BET thin films were found to be dependent on the Eu content. Particularly, the BET films doped with x = 0.75 show better ferroelectric properties (remanent polarization 2Pr = 60.99 C/<TEX>$cm^2$</TEX> and only a little polarization fatigue up to <TEX>$3.5{\times}10^9$</TEX> bipolar switching cycling) than those doped with other Eu contents.

Characteristics of Fatigue Induced by Distribution of Defect Charges in SrBi2Ta2O9 Capacitors

Pt/SrBi2Ta2O9 (SBT)/Pt capacitors have been successfully fabricated using a metalorganic decomposition (MOD) technique. The switchable polarization of SBT capacitors showed a tendency to increase with the number of switching cycles at first and then decrease after 2×109 switching cycles. During the switching process, a competition existed between the depinning behavior of domains and the aggregation of defect charges at the interfaces between SBT thin films and electrodes. It was this competition that determined the fatigue characterization for SBT capacitors. Higher external voltages facilitated the recovery of polarization suppression, which suggests that more domains in the SBT thin films were easily depinned by a higher external field and the pinning depth due to defect charges was different.

MICROSTRUCTURE AND FERROELECTRIC PROPERTIES OF Bi3TiTaO9 THIN FILMS BY METALORGANIC DECOMPOSITION METHOD

ABSTRACT Bismuth titanium tantalum—Bi3TiTaO9 (BTT) thin films with different thickness from 100 nm to 400 nm were successfully fabricated on Pt/Ti/SiO2/Si(100) substrates using modified metalorganic decomposition (MOD) technique at different annealing temperatures. The microstructure of BTT thin films was affected by the film thickness and process temperature. Definite c-axis orientation growth of BTT thin films was found for Pt/Ti/SiO2/Si(100) substrate. The c-orientation ratio and grain size increased with the increase of post annealing temperature. The grain size in BTT thin films annealed at 750°C and 800°C was about 90∼ 100 nm and 150∼ 180 nm, respectively. The higher the process temperature, the higher the c-axis orientation of BTT thin film was. The growth of BTT thin film was affected by the microstructure of the lower layer and the effect of substrate. BTT thin films annealed at 800°C was found to have much improved remanent polarization (Pr) than that at 650°C and 750°C. The Pr and Ec values were measured to be 2 μ C/cm2 and 100 kV/cm, respectively. The critical grain size existed in BTT thin films, and BTT films showed well-defined ferroelectric properties with grain size larger than 100 nm.

Relevance of the pulsed capacitance–voltage measurement technique for the optimization of SrBi 2Ta 2O 9/high-k stack combination to be used in FeFET devices

The ferroelectric field effect transistor (FeFET) with metal–ferroelectric–insulator–semiconductor (MFIS) structure has attracted a lot of interest recently as a nonvolatile memory device. For best performances of FeFET with ferroelectric/high-k gate stacks, the deposition techniques as well as the materials for both the ferroelectric layer and the high-k buffer layer must be carefully selected. In this work, 120 nm SrBi 2Ta 2O 9 (SBT) films were deposited on Al 2O 3 or HfO 2 buffer layers by metal organic chemical vapor deposition (MOCVD) or metal organic decomposition (MOD) techniques. The different SBT/high-k stack combinations were optimized considering not only the remnant polarization of the SBT film, extracted from high-frequency capacitance–voltage (CV) measurements, but also considering the electron trapping–detrapping delay accessed by pulsed CV measurements, which gives insight into the electrical response to very fast program and read pulses. Based on these criteria, the MOCVD SBT/HfO 2 gate stack was found to be the best choice, resulting in a memory window of 0.45 V measured for a gate voltage scan range of only ±5 V. The memory switching occurs at rather low voltage due to the use of thinner SBT than typically reported. This optimized stack combination also exhibited low electron trap density and low leakage.

Optical properties of amorphous Ba0.7Sr0.3TiO3 thin films obtained by metal organic decomposition technique

Barium strontium titanate (BaxSr1−x)TiO3 (BST) thin film deposition techniques are the subjects of many research studies mainly due to their influence on the optical and electrical properties of this material, which are of increasing interest for the processing of optoelectronic integrated circuits. In this study, the amorphous Ba0.7Sr0.3TiO3 (BST0.7) thin films were grown onto fused quartz and silicon substrates at low temperature by using a metal organic decomposition (MOD)-spin-coating procedure from barium 2-caprylate Ba(C8H15O2)2 and 3-methylbutyl acetate CH3COOC2H4CH(CH3)2-based special precursors. The optical constants of amorphous BST0.7 thin films including refractive index, extinction coefficient and optical band gap energies were presented. The calculated extinction coefficient of 214-nm-thick amorphous BST0.7 thin films in visible and near-infrared region was in the order of 10−3, which is much lower than that of polycrystalline BST thin films. The optical band gap energy and refractive index n are estimated to be about 4.27 eV and n=1.94, respectively. The optical propagation loss of the groove optical waveguide with 10 μm width and 185-nm-thick amorphous BST0.7 films was 4.11 dB/cm at a wavelength of 632.8 nm.