PbTiO3 thin films deposited on (001)MgO by the MOCVD technique have been characterized by x-ray diffraction and transmission electron microscopy (TEM). The PbTiO3 films grown at temperatures below Tc (~500 °C) are c-axis oriented polycrystals, while the PbTiO3 films grown at temperatures above Tc are single crystals with a bi-layer structure at room temperature. The top layers of the films near the free surface are c-axis oriented with the orientation relationship of (001)[100]PbTiO3||(001)[100]MgO. The bottom layers of the films near the substrate are a-axis oriented with the orientation relationship of The formation of the bi-layer microstructure of the PbTiO3 films will be discussed in terms of the effect of the cooling rate and the substrate on the phase transition of PbTiO3 from the cubic to the tetragonal phase. When the PbTiO3 films were grown with a large excess of the Pb precursor vapor in the vapor mixture, PbO and PbTiO3 coexisted in the films. Both PbO and PbTiO3 were grown epitaxially on (00l)MgO. The epitaxial orientation relationships were found to be (100) [001]PbO||(001) [100]MgO and (001)[100]PbTiO3||(001)[100]MgO. The 90° domains were observed in the PbTiO3 films deposited at temperatures above Tc. The domain walls are the {101} and {011} twin boundaries, which were formed during the phase transition from the cubic to the tetragonal phase.

Understanding the role of grain boundaries in controlling heat flow is critical to the success of many envisioned applications of nanocrystalline materials. This study focuses on the effect of grain boundaries on thermal transport behavior in nanocrystalline yttria-stabilized zirconia (YSZ) coatings prepared by metal-organic chemical vapor deposition.

Highly oriented PbTiO3 (PT) thin films have been successfully grown on Si(100) using MOCVD technique at as low as 450°C. Titanium isopropoxide, Ti(C3H7O)4, tetraethyl lead, Pb(C2H5 )4, and pure oxygen were chosen as precursor materials in this work. The resulting film chemistry and texture were found to be strongly dependent on Pb/Ti source flow ratio and growth temperature.

Multiferroic nanocomposites, consisting of branched, ferrimagnetic CoFe2O4 filaments and large protruding PbTiO3 particles embedded in a piezoelectric PbTiO3 matrix, have been fabricated by co-deposition using metalorganic chemical vapor deposition. Branched CoFe2O4 filaments reduce the CoFe2O4/PbTiO3 interfacial strain and induce a perpendicular magnetic anisotropy. Three-dimensional characterizations reveal that in addition to the c-domain, grains with a second orientation in PbTiO3 particles contribute to an additional four apparent variants of polarization. In contrast, the PbTiO3 matrix exhibits only c-domain polarization with a smaller magnitude. The smaller piezoresponse results from the constraints imposed by the branched CoFe2O4 filaments. Three-dimensional microstructure and property analysis provide a comprehensive insight on the structure-property relationship of multiferroic nanocomposites grown by metalorganic chemical vapor deposition. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615888]

Lead- and titanium-based oxide thin films were prepared by the metal-organic chemical vapor deposition technique (MOCVD) and the relationship between the film structures and the processing parameters, such as the ratio of Pb/Ti precursors in the gas phase, substrate materials, substrate surface orientation, and growth temperature, was systematically studied. It was found that whether a single-phase stoichiometric PbTiO3 film could be obtained depended on both the Pb/Ti precursor ratio in the gas phase and the deposition temperature. Under appropriate conditions, stoichiometric PbTiO3, films could be obtained on all the substrates including silicon, MgO, α-Al2O3, SrTiO3, and LaAlO3. The PbTiO3 films grown on silicon substrates were always polycrystalline, whereas epitaxial PbTiO3 films were obtainable on all the other substrates. For epitaxial PbTiO3 films, the epitaxial relationship, crystallinity, and domain structures were found to be a function of both the substrate materials and surface orientation as well as the deposition temperature. X-ray rocking curves (ω scan) of the (100) and (001) planes of PbTiO3 epitaxial film and PbTiO3 single crystal revealed the inherent nature of the domain structures in PbTiO3.

We present a data collection approach for nanofocused Bragg coherent x-ray diffraction imaging (CXDI), a technique that can extend the resolution of x-ray nanoprobes and isolate individual nanostructures for study. Nanofocused Bragg CXDI uses hard x-rays focused to <100 nm to measure volumetric diffraction peaks with curved phase illumination. Here, we discuss the experimental challenges associated with this measurement and present the first coherent Bragg volumes measured from an individual beta-Bi2O3 epitaxial nanocrystal.

The preferred orientation, grain morphology, and composition heterogeneity of the polycrystalline Pb(ZrxTi1–x)O3 (PZT) thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and x-ray energy dispersive spectroscopy (EDS). PZT thin films with nominal x = 0.5 were grown by metal-organic chemical vapor deposition (MOCVD) on (110)- and (101)-textured RuO2 bottom electrodes at temperatures ≤525 °C. Columnar grain microstructure with strongly faceted surface morphology was observed in both films. The grain morphology and surface roughness of the PZT films were observed to depend on those of the underlying RuO2 layers. TEM-EDS analysis shows notable cation composition heterogeneity in length scales of 0.2–2 μm. Pronounced Pb composition deficiency and heterogeneity were also observed in PZT/(110)RuO2 in length scales above 40 μm. The grain morphology and cation heterogeneity of the PZT films are discussed on the basis of diffusion-limited columnar growth mechanism.

Metallic RuO2(110) thin films were grown by oxygen-plasma-assisted molecular beam epitaxy (MBE) on MgO(100) and (110) at 425 °C. RuO2 films on MgO(100) are epitaxial with two variants, while RuO2 films on MgO(110) are highly oriented with the (110) face parallel to the substrate surface. The two variants in the RuO2(110) epitaxial films resulted in a twofold mosaic microstructure. The RuO2(110) epitaxial films are very smooth and exhibit a low resistivity of ~36 µΩ-cm. In contrast, the RuO2(110) textured films are very rough, and consist of small grains with a poor in-plane alignment. A slight higher resistivity (49 µΩ-cm) was found for the RuO2(110) textured films grown on MgO(110).

We observe that the high-temperature delta-phase of Bi2O3 is stabilized to room temperature by the epitaxial growth of nanostructures onto either (001)-oriented SrTiO3 or (001)(p)-oriented DyScO3 single crystal substrates. In addition, the morphology can be controlled by the miscut of the substrate. Synchrotron x-ray scattering observations at controlled temperatures and oxygen partial pressures reveal that the delta-Bi2O3 nanostructures are coherently strained to the substrates at room temperature. Annealing the nanostructures at 600 degrees C causes gradual conversion of the (001)-oriented delta-phase to an unidentified strain-relaxed phase.

We have successfully grown epitaxial CoFe2O4 (CFO) thin film on SrTiO3 by metal organic chemical vapor deposition. In order to understand the surface structure and its correlation with magnetic properties, CFO thin films were deposited at a range of deposition temperatures. As the deposition temperature is decreased, a huge effect on film morphology and surface roughness is observed, resulting from a change in the size and density of the crystal nuclei. These changes to grain structure and surface roughness modify the energy landscape of the films and are major contributors to the change in magnetic properties as a function of deposition temperature: the direction of the easy axis is aligned in-plane at lower deposition temperatures and lower anisotropy between different directions is observed in the rough films grown at high temperature.

Combinatorial phage display methods have been used to identify a heptapeptide sequence, ISLLHST, that strongly associates with a perovskite ferroelectric, Pb(ZrxTi1−x)O3 (PZT). The selectively of peptide binding to polycrystalline metalorganic chemical vapor deposition deposited PZT thin films were determined by titering and immunofluorescence microscopy. Ferroelectric properties were determined by measurement of the P-E hysteresis loop on unmodified and phage bound PZT thin films. No change in the coercive field, Ec, or the saturation polarization, Ps was observed. The remnant polarization, PR, however, showed a minor reduction after exposure to aqueous buffer and/or phage binding, possibly due to association of compensating surface charges on the PZT.

Nano-sized TiO 2 particles are of interest for many applications, including use as photocatalysts and in heat transfer fluids (nanofluids). In the present study, TiO 2 nanoparticles with controllable phase and particle size have been obtained through homogeneous gas-phase nucleation using chemical vapor condensation (CVC). The phase and particle size of TiO 2 nanoparticles under various processing conditions have been characterized using x-ray diffraction and transmission electron microscopy. Chamber temperature and pressure were found to be two key parameters affecting particle phase and size. Pure anatase phase was observed for synthesis temperatures as low as 600 °C with chamber pressure varying from 20-50 Torr. When the furnace temperature was increased to 1000 °C at a pressure of 50 Torr, a mixture of anatase and rutile phases was observed, with the predominant phase being anatase. The average particle size under all the experimental conditions was observed to be less than 20 nm.

We report the observation of periodic 180 degrees stripe domains below the ferroelectric transition in thin films. Epitaxial PbTiO3 films of thickness d=1.6 to 42 nm on SrTiO3 substrates were studied using x-ray scattering. Upon cooling below T(C), satellites appeared around Bragg peaks indicating the presence of 180 degrees stripe domains of period Lambda=3.7 to 24 nm. The dependence of Lambda on d agrees well with theory including epitaxial strain effects, while the suppression of T(C) for thinner films is significantly larger than that expected solely from stripe domains.

We present in situ surface x-ray scattering measurements of PbTiO3 epitaxy by metal–organic chemical-vapor deposition. Oscillations in crystal truncation rod intensity corresponding to layer-by-layer growth are observed under a variety of growth conditions. At lower PbO overpressures, we observe a transition to step-flow growth and an increased rate of recovery after growth, indicating a higher surface mobility.