Metallo-organic Decomposition Process Research Articles

Investigation on multiferroic, optical and photoluminescence properties of CoFe2O4/(Pb1−xSrx)TiO3 nanostructured composite thin films

Multiferroic nanostructured composite thin films consisting of CoFe2O4 (CFO) and Pb1−xSrxTiO3 (PST; x = 0.1, 0.2, 0.3, 0.4 and 0.5) layers have been deposited on Pt/TiO2/SiO2/Si and quartz substrates by using metallo-organic decomposition process and spin coating. The effect of Sr content on the multiferroic and optical properties have been investigated. The phase purity such as spinel structure of CFO and perovskite structure of PST has been verified by X-ray diffraction. Cross-sectional scanning electron microscopy images revealed clear interface between CFO and PST layers without any noticeable diffusion. The multiferroic properties of CFO/PST composite films have been confirmed by magnetic and ferroelectric hysteresis loops with low leakage current density. The residual strain sensitivity of multiferroic and optical properties has been observed in the composite films. The decrease in saturation magnetization and saturation polarization with increase in Sr content has been observed which could be attributed to the decrease in residual strain of CFO/PST composite films. The magnetic phase transition temperature of the CFO/PST composite films is also reduced. The optical refractive index decreases with increase of amount of Sr content. The photoluminescence spectra of the CFO/PST composite films possess a blue shift which can be attributed to the Pb and oxygen vacancies as localized sensitizing centers. We show that the multiferroic and optical properties of the CFO/PST composite films are highly sensitive to the heterostructure strains which can be controlled by Sr content.

Multiferroic and magnetoelectric properties of CoFe2O4/Pb1−xSrxTiO3 composite films

To realize multiferroic and magnetoelectric properties, bi-layered nanocomposite films consisting of CoFe2O4 (CFO)/Pb1−xSrxTiO3 (PST) phases (x = 0.1, 0.2, and 0.3) have been deposited on Pt/TiO2/SiO2/Si substrate by using a metallo-organic decomposition process. Both the PST perovskite and the CFO spinel phases are confirmed from X-ray diffraction patterns and Raman spectra of the composite films. The composite films exhibit room temperature multiferroic properties. The values of saturation magnetization (Ms), remanent magnetization (Mr), and coercive field (Hc) of the composite films are in the range of 108–119 kA/m, 42–51 kA/m, and 44.5–64.1 kA/m, respectively. In addition, the saturation polarization (Ps), remanent polarization (Pr), and electrical coercive field (Ec) are observed in the range of 11.3–14.4 μC/cm2, 2.9–4.8 μC/cm2, and 56–59.5 kV/cm, respectively. The dielectric response in the presence of applied magnetic field, Hdc ∼ 238.6 kA/m shows a high magnetocapacitance value ∼385% at frequency 100 kHz for CFO/PST composite film with x = 0.1. The maximum magnetoelectric voltage co-efficient value, αE ∼ 380 kV/(m × T) has been achieved in the composite films with x = 0.1. The influence of elastic/and or interfacial strain on multiferroic magnetoelectric properties is evident from the results.

Study of structure of the TiO2–MoO3 bilayer films by Raman spectroscopy

In this work, TiO2–MoO3 films were easily prepared by dip-coating technique and metallo-organic decomposition process (MOD). Raman analyses indicate the formation of TiO2 in anatase phase and orthorhombic phase of α-MoO3. It was observed that the Raman bands intensities attributed to TiO2 and MoO3 oxides were dependent on the number of decomposition–deposition cycles (DDC). The different number of DDC generates films with different thicknesses and the Raman signal was sensitive to this variation. Raman analyses provided qualitative information about the bilayer structure of the bi-component TiO2–MoO3 films, which was confirmed by scanning electron microscopy. In this direction, the dip-coating technique and MOD process can be an efficient strategy to facile preparation of many samples to be used in applications.

Raman spectroscopy as a tool for the elucidation of nanoparticles with core–shell structure of TiO 2 and MoO 3

In this work, we report the synthesis of TiO 2 nanoparticles and core–shell TiO 2–MoO 3 and MoO 3–TiO 2 nanoparticles dispersed into porous Vycor glass by the metallo-organic decomposition process (MOD). The nanoparticles were analyzed using Raman spectroscopy by monitoring the E 2g band (phonons region for anatase TiO 2) and the bands located at 820 and 996 cm −1 (vibrational modes of α-MoO 3) when Mo is present. The diameters of the TiO 2 nanoparticles dispersed in the glass matrix were calculated by means of the phonon confinement model and the values obtained are 3.9, 4.6, and 5.7 nm depending on the number of impregnation–decomposition cycles used in the nanoparticle syntheses.

Electrical characteristics of BaTiO 3/ Bi 0.5K 0.5TiO 3 multilayered thin films synthesized via metalloorganic decomposition

Multilayered BaTiO 3(BTO)/Bi 0.5K 0.5TiO 3 (BKT) thin films have been fabricated on Pt/Ti/SiO 2/Si substrates using a metalloorganic decomposition process. XRD investigation of the resultant BTO/BKT multilayered thin films shows that they retain a perovskite-related structure type. They also exhibit a well-defined, polarization–electric field hysteresis loop with a measured remnant polarization (2 P r) of 5 µC/cm 2 at an applied electric field of 250 kV/cm. The measured dielectric constant and dielectric loss at 10 kHz is 470 and 0.07 respectively. These multilayer BTO/BKT films maintain an excellent fatigue-free character even after 10 9 switching cycles. The mechanism associated with the enhancement of the electrical properties of the synthesized BTO/BKT films is also discussed.

γ -Fe 2 O 3 nanoparticles dispersed in porous Vycor glass: A magnetically diluted integrated system

An investigation of the effect of interparticle interaction and particle size distribution has been carried out on iron oxide nanoparticles dispersed into porous Vycor glass. γ-Fe2O3 nanoparticles dispersed into monoliths of Vycor glass were obtained using impregnation-decomposition cycles through the single-source metallo-organic decomposition process. Magnetic properties were investigated by ac magnetic susceptibility measurements, as a function of temperature at different frequencies, by measuring zero-field-cooled and field-cooled magnetization curves and by constructing hysteresis loops at different temperatures. A log-normal size distribution of monodomain nanoparticles has been deduced from the analysis of the magnetization curves. F57e Mössbauer spectroscopy was also employed for investigating the magnetic behavior as a function of nanoparticle size. The systems exhibit typical superparamagnetic behaviors with a wide particle size distribution that can be changed without significantly affecting the interparticle interaction. The experimental data are discussed in terms of the evolution of the particle size distribution with the number of impregnation-decomposition cycles used for preparing the nanoparticles.

POLYMER-ASSISTED MOD PREPARATION OF PbZr0.52Ti0.48O3 THICK FILMS FOR MEMS APPLICATIONS

ABSTRACT PbZr0.52Ti0.48O3 (PZT) (52/48) thick films with thickness between 1–5 μ m have been prepared by a metallo-organic decomposition process modified by polymer, poly(vinyl acetate) (PVAc). It has been found that PVAc can increase the single-layer thickness of PZT films. The PZT films with a single-layer thickness over 0.3 μ m have been obtained. The crack-free PZT films annealed at 650–700°C for 3 min exhibit a pure perovskite phase and good electrical properties with dielectric constant between 800–1200, dielectric loss less than 5%, remnant polarization around 28 μ C/cm2 and coercive field less than 100 kV/cm. PZT thick films prepared in this study are promising materials for MEMS applications.

Low Temperature Crystallization and Thick Single Layer of PbTiO3 Thin Film by Metallo-Organic Compound Decomposition with an Additive of PVAC

Polyvinyl acetate (PVAC) has been investigated as an additive in a metallo-organic decomposition process to increase the single-layer thickness and reduce the crystallization temperature of PbTiO 3 thin films. It has been found that PbTiO 3 thin films obtained are dense and crack-free. PVAC can reduce the crystallization temperature of PbTiO 3 thin films from 550°C to 450°C. The single-layer thickness of the crack-free films increases from 0.08 μ m to 0.83 μ m by adding PVAC in PbTiO 3 precursor solutions. Adding PVAC in PT precursor solutions can effectively improve the preparing process of PbTiO 3 thin films and make it more compatible with an IC process.

Characterization of nanosized TiO2 synthesized inside a porous glass–ceramic monolith by metallo-organic decomposition process

This work reports the preparation of TiO2 by decomposition of a metallo-organic precursor (MOD process) in the pores of an α-NbPO5 glass–ceramic monolith (PGC-NbP) and the study of the TiO2 anatase–rutile transition phase. The impregnation of titanium di-(propoxy)-di-(2-ethylhexanoate) in the PGC-NbP was confirmed by diffuse reflectance infrared spectroscopy. In the restrictive porous environment the decomposition of the metallo-organic compound exhibits a lower initial decomposition temperature but a higher final decomposition temperature, in comparison to the free precursor. The pure TiO2 rutile phase is formed only above 700°C when the titanium precursor is decomposed outside the pores. The TiO2 anatase obtained inside the PGC-NbP was stabilized up to 750°C and exhibits a smaller average crystallite size in comparison with the MOD process performed without PGC-NbP. Furthemore, the temperature of the TiO2 anatase–rutile transformation depends on crystallite size, which was provided by XRD and Raman spectroscopy. The precursor impregnation–decomposition cycle revealed a linear mass increment inside PGC-NbP. Micro-Raman spectroscopy shows the presence of a gradient concentration of the TiO2 inside the PGC-NbP. The use of the MOD process in the PGC-NbP pores has several advantages: control of the amount and the nature of the phase formed and preservation of the pore structure of PGC-NbP for subsequent treatments and reactions.

Synthesis of lead zirconate titanate nanofibres and the Fourier-transform infraredcharacterization of their metallo-organic decomposition process

We have synthesized Pb(Zr0.52Ti0.48)O3 fibres with diameters ranging from 500 nm to several microns using electrospinning andmetallo-organic decomposition techniques (Wang et al 2002 Mater. Res. Soc. Symp. Proc. 702359). By a refinement of our electrospinning technique, i.e. by increasing the viscosity of theprecursor solution, and by adding a filter to the tip of the syringe, the diameter of thesynthesized PZT fibres has been reduced to the neighbourhood of 100 nm. The complexthermal decomposition was characterized using Fourier-transform infrared (FTIR)spectroscopy and x-ray diffraction (XRD). It was found that alcohol evaporated duringelectrospinning and that most of the organic groups had pyrolysed before the intermediatepyrochlore phase was formed. There is a good correspondence between XRD and FTIRspectra. We also verify that a thin film of platinum coated on the silicon substratecatalyses the phase transformation of the pyrochlore into the perovskite phase.

Structural evolution and optical properties of Cd 2Nb 2O 7 films prepared by metallo-organic decomposition

Cd 2Nb 2O 7 films were prepared by the metallo-organic decomposition process. Fused quartz supports were dip-coated in a xylene solution containing the synthesized metallo-organic precursors, cadmium di-(2-ethyl-hexanoate) and niobium tri-(ethoxy)-di-(2-ethyl-hexanoate). The deposited films were annealed at temperatures ranging from 500 to 800 °C. X-ray diffraction revealed that only the pyrochlore phase is formed at an annealing temperature of 500 °C. Raman microprobe spectroscopy was used to evaluate crystal symmetry modifications of the films caused by increasing the annealing temperature. The optical parameters of the films on fused quartz were deduced from spectrophotometric measurements. At a wavelength of 1000 nm, the refractive indices and film thicknesses were 1.75 (717±50 nm), 1.61 (1074±28 nm), 1.62 (773±193 nm), 1.68 (1048 nm) and 1.65 (2049±393 nm) for annealing temperatures of 500, 550, 600, 650 and 750 °C, respectively. The average optical energy gap was 4.3±0.1 eV. The microstructure of Cd 2Nb 2O 7 films recorded by scanning electron microscopy and atomic force microscopy were characterized by spherical aggregates with roughness of 17 nm.

A study on abnormal electric properties of lead lanthanum titanate thin films caused by excess PbO

Lead lanthanum titanate (PLT) thin films with excess PbO from 0 to 20 mol.% were prepared by metallo–organic decomposition process. Ferroelectric properties and C– V characteristics of PLT films were investigated as a function of excess PbO. Abnormal ferroelectric and C– V properties were observed in PLT films with excess PbO. P– E hysteresis loops were pinched before saturation of polarization of the films C– V curves had four peaks instead of two peaks in the normal C– V curves. The abnormal level of hysteresis loops and C– V curves are getting worse with increasing amount of excess PbO in the films. The above experimental results can be explained by ferroelectric pinning effect.

The photoinduced metallo-organic decomposition process: a novel technique for dielectric thin-film growth

A novel photoinduced metallo-organic decomposition (PIMOD) process has been developed for growing high-quality lithium niobate films on silicon or sapphire substrates. Crack- and interdiffusion-free films have been grown by the PIMOD process at a lower temperature for a shorter processing time than those required for the conventional MOD process. The electrical, optical, and electrooptical properties of the PIMOD-derived films are reported. >

Processing and electrical properties of Pb (ZrxTi1−x)O3 (x=0.2–0.75) films: Comparison of metallo-organic decomposition and sol-gel processes

The deposition of thin Pb(ZrxTi1−x)O3 films by sol-gel and by metallo-organic decomposition (MOD) processes has been studied. Powders obtained from different precursor solutions were analyzed with respect to their decomposition and crystallization. Using a spin-coating technique, Pb(ZrxTi1−x)O3 films with zirconium concentrations ranging from x=0.2 to 0.75 have been deposited on Pt-electroded Si wafers. The lattice constants of the perovskite films and their dielectric and ferroelectric properties (permittivity, remanent polarization, coercive field strength) have been measured as a function of the zirconium concentration. The results are compared to the data obtained on bulk ceramics. For Pb(ZrxTi1−x)O3 films with a composition located at the morphotropic phase boundary (x≊0.53) the influence of the processing and the lead excess of the starting solutions on the film properties was examined. First measurements on the resistance degradation of thin Pb(Zr0.53Ti47)O3 films deposited by the MOD process are reported.

Metallo-organic decomposition technology for PZT films in memory applications

Metallo-organic decomposition (MOD) technology has been used to produce ferroelectric lead zirconate titanate (PZT) thin films for memory applications. The important advantages of films prepared by the MOD process over other conventional technologies include: low-temperature processing of the equilibrium phases; high purity; near-theoretical density; easy control of stoichiometry; uniform composition even with ppm dopant levels; and grain-size control. PZT films produced by MOD technology are able to achieve a memory having high density, non-volatility of charge, radiation immunity, and the storage of information for a long time without power supply. It has been demonstrated that MOD processing can produce nearly pin-hole-free PZT films on Si wafers. The electrical polarizations and switching characteristics of the PZT films achieved are promising.

Metallo-organic decomposition technology for PZT films in memory applications

Metallo-organic decomposition (MOD) technology has been used to produce ferroelectric lead zirconate titanate (PZT) thin films for memory applications. The important advantages of films prepared by the MOD process over other conventional technologies include: low-temperature processing of the equilibrium phases; high purity; near-theoretical density; easy control of stoichiometry; uniform composition even with ppm dopant levels; and grain-size control. PZT films produced by MOD technology are able to achieve a memory having high density, non-volatility of charge, radiation immunity, and the storage of information for a long time without power supply. It has been demonstrated that MOD processing can produce nearly pin-hole-free PZT films on Si wafers. The electrical polarizations and switching characteristics of the PZT films achieved are promising.

Indium tin oxide films from metallo-organic precursors

Tin-doped indium oxide (ITO) films were prepared by the metallo-organic decomposition process to have nominal composition In 1.91Sn 0.09O 3. The films were prepared by spinning a solution of the metallo-organic precursors on various substrates, firing the organic films to 550 °C in air and then annealing at various temperatures in air. The effect of annealing temperature on grain size, resistivity, Hall mobility and transmittance was studied. It was determined that the films were degenerate n-type semiconductors, and the transmittance of ITO films annealed at 650 °C was greater than 95% in the 450–1000 nm wavelength range.