Paul Zschack

c-axis oriented epitaxial BaTiO3 films on (001) Si

c-axis oriented epitaxial films of the ferroelectric BaTiO3 have been grown on (001) Si by reactive molecular-beam epitaxy. The orientation relationship between the film and substrate is (001) BaTiO3‖(001) Si and [100] BaTiO3‖[110] Si. The uniqueness of this integration is that the entire epitaxial BaTiO3 film on (001) Si is c-axis oriented, unlike any reported so far in the literature. The thermal expansion incompatibility between BaTiO3 and silicon is overcome by introducing a relaxed buffer layer of BaxSr1−xTiO3 between the BaTiO3 film and silicon substrate. The rocking curve widths of the BaTiO3 films are as narrow as 0.4°. X-ray diffraction and second harmonic generation experiments reveal the out-of-plane c-axis orientation of the epitaxial BaTiO3 film. Piezoresponse atomic force microscopy is used to write ferroelectric domains with a spatial resolution of ∼100nm, corroborating the orientation of the ferroelectric film.

Lower limit to the lattice thermal conductivity of nanostructured Bi2Te3-based materials

We investigate the lower limit to the lattice thermal conductivity of Bi2Te3 and related materials using thin films synthesized by the method of elemental reactants. The thermal conductivities of single layer films of (Bi0.5Sb0.5)2Te3 and multilayer films of (Bi2Te3)m(TiTe2)n and [(BixSb1−x)2Te3]m(TiTe2)n are measured by time-domain thermoreflectance; the thermal conductivity data are compared to our prior work on nanocrystalline Bi2Te3 and a Debye–Callaway model of heat transport by acoustic phonons. The homogeneous nanocrystalline films have average grain sizes 30<d<100 nm as measured by the width of the (003) x-ray diffraction peak. Multilayer films incorporating turbostratic TiTe2 enable studies of the effective thermal conductivity of Bi2Te3 layers as thin as 2 nm. In the limit of small grain size or layer thickness, the thermal conductivity of Bi2Te3 approaches the predicted minimum thermal conductivity of 0.31 W/m K. The dependence of the thermal conductivity on grain size is in good agreement with...

Time-resolved study of SrTiO3 homoepitaxial pulsed-laser deposition using surface x-ray diffraction

Homoepitaxy of SrTiO3 by pulsed-laser deposition has been studied using in situ time-resolved surface x-ray diffraction in the temperature range of 310 °C to 780 °C. Using a two-detector configuration, surface x-ray diffraction intensities were monitored simultaneously at the (0 0 12) specular and the (0 1 12) off-specular truncation rod positions. Abrupt intensity changes in both the specular and off-specular rods after laser pulses indicated prompt crystallization into SrTiO3 layers followed by slower intra- and interlayer surface rearrangements on time scales of seconds. Specular rod intensity oscillations indicated layer-by-layer growth, while off-specular rod intensity measurements suggested the presence of transient in-plane lattice distortions for depositions above 600 °C.

Quadrupole lamp furnace for high temperature (up to 2050 K) synchrotron powder x-ray diffraction studies in air in reflection geometry

A four-lamp thermal image furnace has been developed to conduct high temperature x-ray diffraction in reflection geometry on oxide ceramic powder samples in air at temperatures ⩽2050K using synchrotron radiation. A refractory crucible made of Pt20%Rh alloy was used as a specimen holder. A material with well characterized lattice expansion properties was used as an internal crystallographic thermometer to determine the specimen temperature and displacement. The performance of the apparatus was verified by measurement of the thermal expansion properties of CeO2, MgO, and Pt which were found to be within ±3% of the acceptable values. The advantages, limitations, and important considerations of the instrument developed are discussed.

Charge transport and magnetization profile at the interface between the correlated metal CaRuO3 and the antiferromagnetic insulator CaMnO3

A combination of spectroscopic probes was used to develop a detailed experimental description of the transport and magnetic properties of superlattices composed of the paramagnetic metal CaRuO

Designed Synthesis, Structure, and Properties of a Family of Ferecrystalline Compounds [(PbSe)1.00]m(MoSe2)n

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Achromatic nested Kirkpatrick–Baez mirror optics for hard X-ray nanofocusing

and the antiferromagnetic insulator CaMnO

Controlling Size-Induced Phase Transformations Using Chemically Designed Nanolaminates

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Structure of the TiO2−x(100)-1×3 surface by direct methods

. The charge carrier density and Ru valence state in the superlattices are not significantly different from those of bulk CaRuO

Elastic anomaly for Sr Ti O 3 thin films grown on Si(001)

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