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Epitaxial Thin Films (epitaxial + thin_film)
Selected AbstractsThermoelectric Performance of Epitaxial Thin Films of Layered Cobalt Oxides Grown by Reactive Solid-Phase Epitaxy with Topotactic Ion-Exchange MethodsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2007Kenji Sugiura This article reviews high-quality epitaxial film growth of layered cobalt oxides by reactive solid-phase epitaxy (R-SPE) with topotactic ion-exchange methods. Epitaxial film of Na0.8CoO2 was grown on a (0001)-oriented ,-Al2O3 substrate by R-SPE using CoO film as the starting material. The Na0.8CoO2 epitaxial films were converted into high-quality epitaxial films of Sr0.32Na0.21CoO2 and [Ca2CoO3]xCoO2 by topotactic ion-exchange methods. The Sr0.32Na0.21CoO2 film exhibited better stability against moisture than that of the Na0.8CoO2 film, while it retained the good thermoelectric properties of Na0.8CoO2. The [Ca2CoO3]xCoO2 film exhibited a high electrical conductivity of 2.95 × 102 S/cm and a large Seebeck coefficient of +125 ,V/K at 300 K. [source] Molecular Auxetic Behavior of Epitaxial Co-Ferrite Spinel Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Matjaz Valant Abstract In functional oxide materials so-called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of ,0.85. A hinge-like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano-devices. [source] Ferroelectric Switching in Multiferroic Magnetite (Fe3O4) Thin FilmsADVANCED MATERIALS, Issue 44 2009Marin Alexe Real-time ferroelectric polarization switching in magnetite epitaxial thin films is reported, proving that magnetite is not only historically the first material showing magnetism and correlated electron properties, but also that it is ferroelectric with a value of the ferroelectric polarization approaching that of well-known ferroelectric materials such as BaTiO3. [source] Growth of magnetite epitaxial thin films by gas flow sputtering and characterization by FMRIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2007Hiroshi Sakuma Member Abstract The growth of magnetite (Fe3O4) epitaxial thin films on MgO substrates were studied by using gas flow sputtering (GFS). Reflection high-energy electron diffraction (RHEED) and atomic force microscopy showed that the surfaces of the films obtained at a substrate temperature Ts of 300 °C and oxygen flow rates FO2 of 0.12 , 0.18 sccm are fairly flat for the film thickness of about 200 nm. The saturation magnetization and resistivity were close to the reported values of Fe3O4 for Ts= 300°C and FO2 = 0.12,0.20sccm. The films obtained at Ts= 300°C and FO2=0.16 and 0.18 sccm showed Verwey transition, which is persuasive evidence of the formation of Fe3O4. The epitaxial relationship of Fe3O4(100)//MgO(100) and Fe3O4[100]//MgO[100] was confirmed by using ferromagnetic resonance (FMR), and the anisotropy constants and magnetization were obtained by the fitting of resonance-field versus applied-field angle curves. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Fabrication study of AlN solar-blind (<280,nm) MSM photodetectors grown by low-temperature depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010Meei-Ru Chen Abstract AlN, an important semiconductor with the widest band gap among III-nitrides, was employed to construct solar blind metal,semiconductor,metal photodetectors (MSM-PDs). MSM-PDs were fabricated on AlN epitaxial thin films deposited on GaN/sapphire using a helicon sputtering system at a low temperature of 300,°C. The dark current of the device is as low as 200,fA at 20,V and the photocurrent illuminated by a D2 lamp increases more than two orders of magnitude. The photocurrent increases almost linearly with the incident optical power at the wavelength of 200,nm. The results show that the low temperature grown AlN MSM device is suitable for the application of deep UV detection. [source] A comprehensive investigation of the structural properties of ferroelectric PbZr0.2Ti0.8O3 thin films grown by PLDPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009David Walker Abstract X-Ray diffraction investigations were made of high-quality epitaxial thin films of the ferroelectric material lead zirconate titanate, PbZr0.2Ti0.8O3 (PZT), grown by pulsed laser deposition (PLD). Layers from 7 to 200,nm in thickness were studied, deposited on a 30,nm SrRuO3 (SRO) electrode on a [001] oriented SrTiO3 (STO) substrate. The out-of-plane lattice parameters of the PZT films were measured by high-resolution X-ray diffraction using CuK,1 radiation. A significant enhancement of the c lattice parameter with film thickness was observed, the maximum value of 4.25,Å reached in the 30,50,nm thick films. For film thicknesses greater than 100,nm, the c lattice parameter is relaxed, towards the bulk value of 4.13,Å at this composition. The in-plane lattice parameters were studied by Grazing incidence X-ray scattering (GIXS), using 15,keV synchrotron radiation at I16, Diamond. The a lattice parameter of domains with [001] oriented normal to the sample surface was effectively lattice matched to the SRO layer in the 7,nm ultra-thin film, but relaxed compared to the SRO in thicker films. The tetragonality of the [001] oriented domains decreases with increasing film thickness, approaching the bulk value of 1.05 in the thickest films. Evidence for the presence of [100] oriented a -domains was found in PZT films as thin as 30,nm, the proportion of which increased with increasing film thickness, suggesting they grow in order to relieve stresses that would prevent the epitaxial growth of thicker PZT films. The a -domains in the thicker films were found to be located nearer to the PZT/SRO interface than to the top surface of the PZT. [source] Conversion of an electron,hole plasma into a high density excitonic state in ZnO epitaxial thin filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004Y. Toshine Abstract Time-resolved luminescence spectra of an exciton-exciton scattering process and an electron,hole plasma (EHP) were measured in ZnO epitaxial thin films by the optical Kerr gate method. At moderate excitation density below critical Mott density, stimulated emission of luminescence due to the exciton,exciton scattering process (P band) was observed. The P band shows a red shift and spectral narrowing in the first 1,2 ps after the excitation which reflects a thermal redistribution of excitons in the n = 1 excitonic state. On the other hand, at high excitation density above the critical Mott density, stimulated emission of the luminescence due to the EHP was observed. After thermalization of the EHP, the luminescence intensity of the EHP band decreases with time, and the EHP band converts to the P band after ,10 ps through a reverse Mott transition. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||