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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Domain orientation in ultrathin (Ba,Sr)TiO3 films measured by optical second harmonic generation

E. D. Mishina, N. E. Sherstyuk, D. R. Barskiy, A. S. Sigov, Yu. I. Golovko, V. M. Mukhorotov, M. De Santo, and Th. Rasing

J. Appl. Phys. 93, 6216 (2003); http://dx.doi.org/10.1063/1.1563849 (7 pages) | Cited 12 times

Online Publication Date: 9 May 2003

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The analysis of polarization diagrams for specular and scattered second harmonic generation (SHG) was used for the structural characterization of submicron domain structures of thin (Ba,Sr)TiO3 (BST) films. It is shown that the lack of separation of these two contributions may lead to completely wrong conclusions about the domain orientation in these films. SHG studies of the thickness dependence of domain fractions (including 180° domains) reveal the presence of ferroelectric domains in ultrathin BST films (6 nm), although no domain structure was observed by atomic force microscopy. Thus the presence of ferroelectric ordering was demonstrated in perovskite films with a thickness down to 6 nm. © 2003 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization

Optical and electrical properties of Pr0.8Sr0.2MnO3 thin films

Toshio Suzuki, Piotr Jasinski, Vladimir Petrovsky, Xiao-Dong Zhou, and Harlan U. Anderson

J. Appl. Phys. 93, 6223 (2003); http://dx.doi.org/10.1063/1.1566456 (6 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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The results of studies on the preparation, structure, optical, and electrical properties of Pr0.8Sr0.2MnO3 thin films were presented. Dense films with a thickness of 50–70 nm were produced on monocrystalline sapphire substrates using a polymeric precursor spin coating technique. The results of the optical measurements were correlated with the annealing temperatures of the films and showed that the shape of the optical spectra changed as the structure changed from an amorphous to crystalline structure. The optical spectra was also used to determine the energy dependence of the absorption coefficient. The electrical conductivity was observed to be about three orders of magnitude higher for specimens which were crystalline as compared to amorphous. © 2003 American Institute of Physics.
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78.66.-w Optical properties of specific thin films
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.-y Defects and impurities in crystals; microstructure
61.72.Cc Kinetics of defect formation and annealing
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Tv Optical and dielectric properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
61.66.Fn Inorganic compounds
61.43.-j Disordered solids
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Microstructure of annealed magnetic tunnel junction by electron microscopy

Q. Y. Xu, Y. G. Wang, Z. Zhang, B. You, J. Du, and A. Hu

J. Appl. Phys. 93, 6229 (2003); http://dx.doi.org/10.1063/1.1567037 (5 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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Transmission electron microscopy, high-resolution electron microscopy, and electron holography were used to study the microstructure of CoFe/AlOx/Co magnetic tunnel junctions (MTJs) isochronally annealed up to 400 °C. A potential barrier across the metal/oxide interfaces was observed for the as-deposited MTJ sample, and was changed into a well for the MTJ samples annealed at 200 and 400 °C, respectively. A shallow potential well was found when the MTJ was annealed at 200 °C and the well became deeper as the annealing temperature increased to 400 °C. The potential change may attribute to the formation of nonmagnetic metallic Al atoms or clusters when the MTJ sample was annealed at 200 °C and the rest content of the barrier layer was more close to Al2O3, which results in the enhancement of tunneling magnetoresistance (TMR). When the MTJ sample was annealed at 400 °C, more Co and Fe atoms or clusters might diffuse from the ferromagnetic layers into the barrier layer, resulting in the deeper well, and thus significantly decrease the TMR value due to the severe spin-flip scattering. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.-m Magnetotransport phenomena; materials for magnetotransport
68.35.Fx Diffusion; interface formation
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.50.Bb Fe and its alloys
81.40.Gh Other heat and thermomechanical treatments
75.50.Cc Other ferromagnetic metals and alloys
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)

Generation of ferroelectric domains in atomic force microscope

M. Molotskii

J. Appl. Phys. 93, 6234 (2003); http://dx.doi.org/10.1063/1.1567033 (4 pages) | Cited 72 times

Online Publication Date: 9 May 2003

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A theory of an equilibrium shape of domains formed in an electric field of atomic force microscope (AFM) is proposed. The domain shape depends on parameters of the ferroelectric and on the applied voltage. Under low voltages the length and the diameter of the domain are of the same order of magnitude. With voltage increase the ratio between the length and the diameter increases. A correlation between the lateral sizes and the spontaneous polarization value is considered. It is shown that under the same voltage the thinnest domains are formed in ferroelectrics with high spontaneous polarization. The concept of the domain shape invariant as a combination of the domain length and lateral size, which is constant when changing the AFM parameters, is introduced. Results of the calculation of the invariant value in barium titanate as well as of the domain dimensions and the shape in GASH are in good agreement with the experiment. © 2003 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
07.79.Lh Atomic force microscopes

Model of the plane laminar PbTiO3 thin film domain structure on MgO substrate

L. Lahoche, V. Lorman, S. B. Rochal, and J. M. Roelandt

J. Appl. Phys. 93, 6238 (2003); http://dx.doi.org/10.1063/1.1567795 (10 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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Superstructure formation is examined as a strain relaxation mechanism for polydomain structure in an “utlrathin” film on a cubic substrate. A phenomenological model of the dielectric and mechanical behavior of the ferroelectric PbTiO3 film on an MgO oxide substrate is proposed. The case of a laminar 90° domain structure with the walls tilted to 45° with respect to the film/substrate interface is considered. Taking account an inhomogeneous film–substrate coupling related to the superstructure formation and a dislocation propagation mechanism, we investigate strain relaxation and its effect on the domain structure, electrical and mechanical properties as a function of the film thickness, and temperature. It is shown that evolution of the aa-domain abundance in utlrathin film can be related to the film–substrate coupling mechanism expressed in terms of an external to the film inhomogeneous field. Its variation with the film thickness implies the existence of two distinct growth modes influencing the layer texture. For films with a thickness greater than 250 nm, aa-domains abundance is maximum and equal to 18%. For thinner films, c-domains become more stable and their proportion increases up to ∼100% with the appearance of a single domain structure. Numerical modeling of electrical polarization, total strain in both domains, and mean stress in the film is performed for different thicknesses. © 2003 American Institute of Physics.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.72.Bb Theories and models of crystal defects
77.22.Ej Polarization and depolarization
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