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Single-phase electron-doped manganite thin films with nominal composition of La0.7Ce0.3MnO3 (LCeMO) have been prepared on SrTiO3 (100) substrates by pulsed laser deposition. The conditions for obtaining purely single-phase LCeMO films lie within a very narrow window of substrate temperature (Ts∼720 °C) and laser energy density (ED∼2 J/cm2) during deposition. In situ postdeposition annealing, mainly to relax the possible epitaxial in-plane tensile strain between the film and the substrate, leads to an increasing c-axis lattice constant accompanied by the formation of secondary CeO2 phase and higher metal-insulator transition temperature. This is indicative of a strong coupling between the electron and lattice degree of freedom. [ABSTRACT FROM AUTHOR]

Presents a study on the influence of crystal structure on the magnetoresistance of cobalt (Co)/chromium (Cr) multilayers. Characteristics of epitaxial Co/Cr multilayers; Definition of the giant magnetoresistance in multilayers; Effects due to the spin dependent scattering at the interfacial regions of the superlattice.

The properties of Cr-doped GaN epilayers grown by rf-plasma-assisted molecular beam epitaxy were studied. The deep acceptor nature of Cr was used to grow semi-insulating GaN epilayers on sapphire substrates for electronic device applications. The room-temperature (RT) sheet resistivity of the epilayers reached 1010 Ω/square. The activation energy of dark conductivity was about 0.48 eV. Step-graded AlxGa1-xN/GaN (x=0.3-0.2) superlattices (SLs) were designed to filter dislocations. Transmission electron microscopy images showed that the SLs can dramatically reduce dislocation density. Al0.35Ga0.65N/GaN heterostructure grown on Cr-doped semi-insulating GaN epilayer exhibited a RT mobility of 960 cm2/V s and sheet carrier density of 2.1×1013 cm-2. [ABSTRACT FROM AUTHOR]

The authors have fabricated NaxCoO2 thin films via lateral diffusion of sodium into Co3O4 (111) epitaxial films (reactive solid-phase epitaxy [Ohta et al., Cryst. Growth Des. 5, 25 (2005)]). The environment of thermal diffusion is key to the control of the sodium content in thin films. From the results of x-ray diffraction and in-plane ρab, the epitaxial growth and the sodium contents of these films were identified. The thermoelectric measurements show a large thermoelectric power similar to that observed in single crystals. The quasiparticle scattering rate is found to approach zero at low temperatures, consistent with the small residual resistivity, indicating high quality of the NaxCoO2 thin films. [ABSTRACT FROM AUTHOR]

Epitaxial CrO[sub 2] (110)-oriented films were fabricated on Si (100) substrates buffered by rutile TiO[sub 2] derived from oxidation of a pulsed-laser-deposited TiN layer. The epitaxial films of CrO[sub 2] were prepared by chemical vapor deposition in a two-zone furnace with oxygen flow from a CrO[sub 3] precursor. The transport measurements show that the CrO[sub 2] films are metallic with a Curie temperature of about 380 K. The temperature dependence of resistivity was best described by a phenomenological expression ρ(T) = ρ[sub 0] +AT²e[sup (-δ/T)] over the range of 5-350 K with &de;ta= 94 K. The magnetic measurements show the in-plane coercive fields are about 30 and 60 Oe at 300 and 5 K, respectively. The temperature dependent spontaneous magnetization follows Bloch's T[sup 3/2] law and the slope suggests a critical wavelength of λ[sub δ] ∼ 30.6 Å beyond which spin-flip scattering becomes important. [ABSTRACT FROM AUTHOR]