Dipping-pyrolysis Process Research Articles

Transmission Electron Microscopic Studies of YbBa2Cu3O7-δ Superconducting Final Films Formed on LaAlO3(001) Substrates by the Dipping-Pyrolysis Process

We investigated the relationship between final heat-treatment conditions and microstructures of YbBa2Cu3O7-δ films formed on LaAlO3(001) substrates by the dipping-pyrolysis process. First, we spin-coated the substrates with a solution including metal organic compounds. Second, we heated them at 425°C in air to form amorphous precursor films. Finally, YbBa2Cu3O7-δ films were prepared by the final heat-treatment of the precursor films at 750°C in an Ar gas flow under various conditions of heating rate and holding time. The microstructures of these final films were studied by transmission electron microscopy. It has been found that a rapid heating rate is necessary for the epitaxial growth of the superconducting films, and that a long holding time is effective for the grain growth of the crystals. The transmission electron microscopic studies revealed different microstructures of the final films, although X-ray diffraction patterns did not distinguish them.

Preparation of epitaxially grown LaSrCoO3 thin films on SrTiO3(100) substrates by the dipping-pyrolysis process

LaSrCoO3 thin films were spin-coated onto SrTiO3(100) substrates by the dipping-pyrolysis process. X-ray diffraction θ-2θ scans and X-ray diffraction β scans were used to determine the crystallinity and in-plane alignment behavior of the films. The X-ray diffraction pattern shows the film obtained by annealing at 800°C was highly oriented. The X-ray diffraction pole-figure analysis and reciprocal-space mapping (ω-2θ scans) of the resulting film showed that the film comprising the pseudocubic phase had an epitaxial relationship with the SrTiO3 substrate.

Effects of the Heat-Treatment Conditions on Microstructures of YbBa2Cu3O7-σ Superconducting Films Formed by the Dipping-Pyrolysis Process

AbstractYbBa2Cu3O7-σ(Yb123) films were formed on SrTiO3(STO)(001) and LaAlO3(LAO)(001) substrates by the dipping-pyrolysis process. Using transmission electron microscopy, we investigated effects of the heat-treatment conditions in the processes of the dipping-pyrolysis method on microstructures of these films. As a result, we found that the high heating rates at the initial and final heat-treatments are necessary for achieving the epitaxial growth of the superconducting films.

X-Ray Diffraction Studies of Epitaxial La0.5Sr0.5CoO3 Thin Films Prepared by the Dipping-Pyrolysis Process

A reciprocal-space map (ω–2θ scans) can provide more information than conventional X-ray diffraction (XRD) θ–2θ scans. In this study, an epitaxial La0.5Sr0.5CoO3 thin film prepared on the SrTiO3(100) substrate by the dipping-pyrolysis (DP) process was investigated based on XRD θ–2θ scanning, β scanning (pole figure) and asymmetric ω–2θ scanning. An epitaxial La0.5Sr0.5CoO3 film annealed at 800°C was found to consist of the pseudocubic phase with a d∥/d⊥ ratio of 1.005 by reciprocal-space map analysis.

Effects of the Initial Heat-Treatment Conditions on Microstructures of YbBa2Cu3O7-δ Superconducting Final Films Deposited on SrTiO3(001) Substrates by the Dipping-Pyrolysis Process

We investigated by transmission electron microscopy the relationship between the initial heat-treatment conditions and the microstructures of YbBa2Cu3O7-δ superconducting final films deposited by a dipping-pyrolysis process on SrTiO3(001) single crystal substrates. An amorphous precursor film was prepared by heating rapidly up to 425°C. By heat-treating at 725°C, this film became a c-axis oriented YbBa2Cu3O7-δ film with a thickness of 100 nm, and showed a sharp resistive transition around the critical temperature (TC). On the other hand, a polycrystalline precursor film was produced by heating slowly. This film did not give rise to an epitaxial film, but to a YbBa2Cu3O7-δ polycrystalline film with a grain size of about 200 nm, and exhibited a broad transition. Therefore, the initial heat-treatment conditions and the microstructures of the precursor films are important for the epitaxial growth and superconducting properties of the final YbBa2Cu3O7-δfilms.

Effect of substrate material on the crystallinity and epitaxy of Pb(Zr,Ti)O 3 thin films

Pb(Zr,Ti)O 3 thin films (Pb:Zr:Ti=1:0.52:0.48) were prepared on various single-crystal substrates via dipping-pyrolysis process by use of metal naphthenates as starting materials. The alignments of these films were examined by X-ray diffraction (XRD) θ–2 θ scans and β scans (pole figures). The films grown on Nb-doped SrTiO 3, MgO or LaAlO 3 showed an epitaxial relationship with substrates after heat treatment at 750°C, while those grown on sapphire and Si wafers exhibited polycrystalline or amorphous characteristics. Epitaxial films on SrTiO 3 and LaAlO 3 were found to consist of a c-axis oriented tetragonal phase, to minimize the lattice misfit with the substrates. These epitaxial films exhibited very smooth surfaces by SEM and AFM observations. In addition, the fluctuation of in-plane alignment was significantly dependent on the lattice-misfit values.

Dense and smooth epitaxial BaTiO3 thin films by the dipping-pyrolysis process

Dense and smooth BaTiO3 thin films were prepared on SrTiO3 (100) substrates by the dipping-pyrolysis process using a mixed precursor solution of barium and titanium naphthenates. Combination effects of prefiring [at 150–450 °C in air or low oxygen partial pressure, p(O2)[ and final heat treatment [at 850 °C in air or low p(O2)[ on preparation of BaTiO3 thin films were examined. An epitaxial BaTiO3 thin film with a dense and smooth surface consisting of nanosized grains about 70 nm was prepared by prefiring under low p(O2) at 250 °C and final heat treatment under low p (O2) at 850 °C.

Highly oriented Pb(Zr,Ti)O 3 thin films on textured LaNiO 3 electrode by dipping–pyrolysis process

Pb(Zr,Ti)O 3 film was prepared by dipping–pyrolysis process using metal naphthenates as starting materials. X-ray diffraction θ–2 θ scans and β scans (pole figures) showed that a Pb(Zr,Ti)O 3 film with a homogeneous and smooth texture was epitaxially grown on LaNiO 3/SrTiO 3, while a polycrystalline film was formed on LaNiO 3/LaAlO 3.

Epitaxial Pb(Zr,Ti)O 3 thin films on LaAlO 3 (100) by dipping–pyrolysis process

Epitaxially grown Pb(Zr,Ti)O 3 thin films were prepared on LaAlO 3 (100) substrates by the dipping–pyrolysis (DP) process using metal naphthenates as starting materials. Homogeneous Pb–Zr–Ti solutions with toluene were spin-coated onto the substrates and pyrolyzed at 500°C. Highly oriented Pb(Zr,Ti)O 3 films confirmed by X-ray diffraction (XRD) θ–2 θ scans were obtained by annealing at 750°C in air. The XRD pole-figure analysis and reciprocal space mapping of the resulting 0.6 μm films showed that the film comprising the c-axis oriented tetragonal phase have an epitaxial relationship with the LaAlO 3 substrates.

The influence of prefiring conditions on the epitaxy of Pb(Zr,Ti)O 3 films by dipping-pyrolysis process

Pb(Zr,Ti)O 3 (PZT, Pb : Zr : Ti = 1 : 0.52 : 0.48) thin films were prepared by dipping-pyrolysis process using a mixed solution of lead-, zirconium- and titanium-naphthenates. The solution was spin-coated onto MgO(100) substrates and the precursor films were prefired at 200°C; in air or in argon for various holding times, followed by final heat treatment at 750°C. Highly oriented (00 l)/( h00) PZT films with smooth, crack-free surfaces were obtained for all the samples except the films prefired in air for 12 and 24 h. Pyrolysis at a low temperature (200°C) in a non-oxidizing atmosphere (argon) was found to be most important for the epitaxy of product films.

Epitaxial Growth of Bi4Ti3O12 Thin Films on LaAlO3(012) and MgO(100) by Dipping-Pyrolysis Process

Epitaxially grown Bi4Ti3O12 films on LaAlO3(012) and MgO(100) substrates have been prepared by the dipping-pyrolysis process using metal naphthenates. It was confirmed that the degree of epitaxy of the films strongly depends on the lattice misfit between the Bi4Ti3O12 film and the substrate used; the film on LaAlO3(012), with a small lattice-misfit value, showed a high degree of epitaxy in comparison with the film on MgO(100).

X-ray diffraction studies of epitaxial Pb(Zr,Ti)O 3 films prepared by chemical solution method

In this study, epitaxial Pb(Zr,Ti)O 3 thin films prepared on various substrates by dipping-pyrolysis process were investigated using asymmetric X-ray diffraction 2 θ/ ω scans. Epitaxially grown films heat-treated at 750°C on Nb-doped SrTiO 3(100) and LaAlO 3(100) were found by reciprocal-space map analysis to consist of the c-axis-oriented tetragonal phase.

Effect of substrates on epitaxy of Bi 4Ti 3O 12 thin films by dipping—pyrolysis process

Bismuth titanate (Bi 4Ti 3O 12) thin films have been prepared on various substrates by the dipping—pyrolysis process using metal naphthenates as starting materials. The crystallinity and in-plane alignment of the films are analysed by X-ray diffraction θ-2 θ scans and β scans (polar diagrams), respectively. Highly c-axis-oriented Bi 4Ti 3O 12 thin films with smooth surfaces are obtained by heat treatment at 750°C on SrTiO 3 (100), LaAlO 3 (100) and MgO (100) substrates, while films grown on Si (100) exhibit polycrystalline characteristics. The fluctuation of in-plane alignment of epitaxially grown films depends on the lattice-misfit values between the films and the substrates used; Bi 4Ti 3O 12 films on MgO shows the largest full width at half maximum values in their β scans.

Effects of substrate materials and annealing temperature on crystal structure and epitaxy of La 0.7Sr 0.3MnO 3 films via dipping-pyrolysis process

Epitaxially grown La 0.7Sr 0.3MnO 3 (LSMO) films were prepared on SrTiO 3(001), LaAlO 3(001) and MgO(001) single-crystal substrates by dipping-pyrolysis process. The fluctuation of alignments (mosaicity) of the films was evaluated based on X-ray diffraction 2 θ/ θ scans, β scans (pole figures) and asymmetric 2 θ/ ω scans (reciprocal-space maps). Lattice types and epitaxy were examined in the films after heat treatment at 1473–1873 K; the lattice type of the films on SrTiO 3 was pseudocubic, whereas those on LaAlO 3 and MgO were pseudocubic or rhombohedral, depending on the heat-treatment temperature. A mosaic spread (Δ ω) of the LSMO film varied with the lattice-mismatch value between film and substrate. The LSMO films on SrTiO 3 (lattice misfit ≈1%) showed high epitaxy with a low Δ ω (≈0.50°), whereas the films on MgO (misfit ≈8%) exhibited a larger Δ ω (≈2.8°). Also, surface morphology of the film was found to markedly depend on the kind of substrate materials and annealing temperature.

Low temperature solid-state epitaxy of LiNbO3 films by a dipping-pyrolysis process using Li-trifluoroacetate

Epitaxially grown LiNbO3 thin films were prepared on sapphire(012) (R-plane) substrates by a dipping-pyrolysis process using two kinds of lithium sources, i.e., Li-2-ethylhexanoate and Li-trifluoroacetate, which are pyrolyzed in air to Li2CO3 and LiF, respectively. Crystallization temperature and alignment of LiNbO3 films on sapphire(012) were found to depend greatly on the Li sources. Dominantly [100]-oriented epitaxial LiNbO3 films were crystallized at around 600 °C using 2-ethylhexanoate, whereas dominantly [012]-oriented epitaxial LiNbO3 films resulted at a temperature as low as 400 °C using trifluoroacetate.

Preparation of epitaxial Fe3−xO4 films by dipping-pyrolysis process using CO−CO2 gas mixtures

Epitaxially grown Fe3−xO4 films were prepared on MgO(001) substrates by dipping-pyrolysis process using CO–CO2 gas mixtures. The structure and in-plane alignment of these films were examined by x-ray diffraction θ-2θ scans, β scans (pole figures), and asymmetric ω-2θ scans (reciprocal-space maps). The films heattreated at 500 °C and higher in an atmosphere with pCO/pCO2 = 10−4 had a spinel-type structure and were in an epitaxial (cube on cube) relationship with the substrates.

Preparation of Epitaxial Pb(Zr, Ti)O3 Thin Films on Nb-Doped SrTiO3 (100) Substrates by Dipping-Pyrolysis Process

Epitaxially grown Pb(Zr, Ti)O3 (PZT, Pb:Zr:Ti=1:0.52:0.48) thin films were prepared on Nb-doped SrTiO3 (100) substrates by dipping-pyrolysis process with metal naphthenates used as starting materials. The alignments of the films were investigated based on X-ray diffraction (XRD) θ–2θ scans, β scans (pole figures), and asymmetric ω–2θ scans (reciprocal-space maps). Epitaxial films with smooth surfaces were obtained by heat treatment of prefired films at 600°–750° C; a film heat-treated at 750° C showed the strongest peak intensities in the XRD θ–2θ scans. These PZT films were found by reciprocal-space map analysis to consist of the c-axis-oriented tetragonal phase.

Preparation of Epitaxial BaTiO3 Thin Films by the Dipping-pyrolysis Process

Epitaxial BaTiO3 thin films were prepared on SrTiO3 (100) substrates by the dipping-pyrolysis process using metal naphthenates as starting materials. Highly oriented BaTiO3 thin films were crystallized by heat treatment at 800 °C and higher, from amorphous precursor films pyrolyzed at 470 °C. XRD pole-figure and reciprocal-space mapping analyses showed that the films were epitaxially grown on SrTiO3substrates and were pseudocubic phase with an a║/aτ ratio of 1.003, smaller than the c0/a0 ratio (=1.011) of bulk tetragonal BaTiO3.

Carbon dioxide controlled annealing method for preparation of YBa 2Cu 3O 7− y films by dipping-pyrolysis process

A three-step annealing method is proposed for the preparation of highly c-axis-oriented YBa 2Cu 3O 7− y (Y123) films by dipping-pyrolysis (DP) process when the heating rate is relatively low. This method comprises sequential heat treatment with a maximum temperature of 770°C in the following atmospheres: first, high p(CO 2); second, CO 2-free and low p(O 2); and, finally, CO 2-free and high p(O 2). With this annealing method, contamination of a-axis grains is substantially prevented and highly c-axis Y123 films are obtained, because the formation of Y123 grains from the precursor (Y 2O 3BaCO 3CuO) is markedly suppressed under the high- p(CO 2) environment during the heating ramp, at which temperatures a-axis grains tend to grow in the CO 2-free atmospheres.

Preparation of epitaxial La1−xSrxMnO3 films on SrTiO3(001) by dipping-pyrolysis process

La1−xSrxMnO3 (LSMO) (x = 0−0.3) films were prepared on SrTiO3(001) substrates by the dipping-pyrolysis process using metal naphthenates as starting materials. Epitaxially grown LSMO films were obtained by heat treatment at 800–1200 °C; the fluctuation of alignment of these films, evaluated by reciprocal-space mapping of asymmetric x-ray diffraction, was markedly small, as comparable to that of the substrates. The LSMO films with x = 0.1−0.3 showed metallic conduction behavior at 25–300 K, and the resistivity was as low as that of LSMO single crystals, e.g., 4.5 × 10−4 Ω · cm at 150 K for the film with x = 0.3.