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1 Dec 2010

Volume 108, Issue 11, Articles (11xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 108, 111101 (2010); http://dx.doi.org/10.1063/1.3503495 (21 pages)

R. C. Runkle, A. Bernstein, and P. E. Vanier
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back to top Dielectrics and Ferroelectricity

Van der Waals torque induced by external magnetic fields

R. Esquivel-Sirvent, G. H. Cocoletzi, and M. Palomino-Ovando

J. Appl. Phys. 108, 114101 (2010); http://dx.doi.org/10.1063/1.3514152 (5 pages) | Cited 4 times

Online Publication Date: 3 December 2010

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We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III–IV semiconductors such as InSb, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of InSb. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of InSb increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropic materials when the magnetic fields is close to 1 T.
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78.20.Ls Magneto-optical effects

Temperature dependent optical properties of Mn doped (Pb,Sr)TiO3 ferroelectric films in absorption region: Electron–phonon interaction

J. Yang, Y. Q. Gao, J. Wu, Z. M. Huang, X. J. Meng, M. R. Shen, J. L. Sun, and J. H. Chu

J. Appl. Phys. 108, 114102 (2010); http://dx.doi.org/10.1063/1.3516157 (5 pages) | Cited 7 times

Online Publication Date: 3 December 2010

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The 2 mol % Mn doped Pb0.5Sr0.5TiO3 films were fabricated on sapphire substrates by chemical solution deposition. The complex dielectric functions and optical parameters of the films determined by transmittance spectroscopy in a broad temperature range of 80–500 K were investigated. Apparent thermally-driven band-gap energy shrinkage, line-width of interband electron transition broadening and the Urbach band tail behaviors were observed. The results can be mainly correlated with the renormalization of electronic band structure and band-gap energy due to the electron–phonon interaction, which is well established in terms of the Bose–Einstein model.
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78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
71.38.-k Polarons and electron-phonon interactions
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Stress analysis and ferroelectric properties of Pb(Zr0.52Ti0.48)0.96Nb0.04O3 thin film grown on different thickness of BaPbO3 electrodes

Xin-Yi Wen, Jun Yu, Yun-Bo Wang, Wen-Li Zhou, and Jun-Xiong Gao

J. Appl. Phys. 108, 114103 (2010); http://dx.doi.org/10.1063/1.3518516 (7 pages) | Cited 2 times

Online Publication Date: 3 December 2010

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Pb(Zr0.52Ti0.48)0.96Nb0.04O3 (PZTN) thin films were deposited on BaPbO3 (BPO) electrodes by rf-magnetron sputtering. 34, 68, 135, and 270 nm thick BPOs were adopted in this study. The preferred orientation changes from slightly (100)/(001) to slightly (101)/(110) as the BPO thickness increased. The mean grain sizes obtained by Williamson–Hall plots are 81 nm, 120 nm, 146 nm, and 90 nm, respectively. The same tendency was observed by atomic force microscopy method. In residual stress analysis, tensile stress was observed in every film. The stress magnitude is the maximum in the film with 135 nm thick BPO. Through a simple calculation, we suggest that the tensile stress in our films mainly originates from the phase transformation stresses. We also note that the ferroelectric and dielectrics properties are improved with the raise of tensile stresses. A possible reason is that the tensile stress benefits the tetragonal–monoclinic phase transition in the PZTN films with composition near morphotropic phase boundary. The other possible reason is that the raise of the tensile stress is consistent with the increasing of grain size, which decreases the grain boundary density and facilitate domain mobility.
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77.55.fp Other ferroelectric films
68.60.Bs Mechanical and acoustical properties
61.72.Mm Grain and twin boundaries
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
77.80.Dj Domain structure; hysteresis
77.84.Cg PZT ceramics and other titanates

Structural phase transitions of Na(DxH1–x)3(SeO3)2 single crystals studied by observation of 2H and 23Na nuclear magnetic resonance

Ae Ran Lim, Se-Young Jeong, and Sun Ha Kim

J. Appl. Phys. 108, 114104 (2010); http://dx.doi.org/10.1063/1.3510591 (5 pages)

Online Publication Date: 6 December 2010

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Na(DxH1–x)3(SeO3)2 single crystals were grown with a deuterium content of 37%, and the spectra and relaxation times of the 2H and 23Na nuclei in the mixed Na(D0.37H0.63)3(SeO3)2 crystals were measured as functions of temperature. The 2H and 23Na nuclear magnetic resonance (NMR) spectra undergo changes near 213 K. Our 23Na NMR results for x ≥ 0.3 show that there is no triclinic intermediate phase; the paraelectric α-phase and ferroelectric γ-phase arise in mixed Na(D0.37H0.63)3(SeO3)2 crystals. In addition, the 2H and 23Na relaxation times of mixed Na(D0.37H0.63)3(SeO3)2 crystals are different from the 2H and 23Na relaxation times of NaH3(SeO3)2 and NaD3(SeO3)2. The effects of partial deuteration of sodium trihydrogen selenite crystals include not only a shift in the phase transition temperature TC but also a change in the local symmetry.
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77.80.B- Phase transitions and Curie point
76.60.Es Relaxation effects

Temperature-pressure phase diagram and ferroelectric properties of BaTiO3 single crystal based on a modified Landau potential

J. J. Wang, P. P. Wu, X. Q. Ma, and L. Q. Chen

J. Appl. Phys. 108, 114105 (2010); http://dx.doi.org/10.1063/1.3504194 (8 pages) | Cited 8 times

Online Publication Date: 6 December 2010

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A modified eighth-order Landau potential was proposed for the BaTiO3 single crystal by taking account into the quantum mechanical effects at low temperature. While all existing thermodynamic potentials for BaTiO3 fail to accurately describe the pressure dependence of ferroelectric transition temperatures, the temperature and hydrostatic pressure phase diagram constructed using the modified potential shows excellent agreement with experimental measurements by Ishidate, Abe, Takahashi, and Mori [Phys. Rev. Lett. 78, 2397 (1997)] . On the basis of the new proposed Landau potential, we calculated the dielectric coefficients, spontaneous polarizations, temperature-electric field phase diagram, and piezoelectric coefficients, all in good agreement well with existing experimental data.
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77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants
05.70.Ce Thermodynamic functions and equations of state

Thickness effect on the dielectric, ferroelectric, and piezoelectric properties of ferroelectric lead zirconate titanate thin films

J. Pérez de la Cruz, E. Joanni, P. M. Vilarinho, and A. L. Kholkin

J. Appl. Phys. 108, 114106 (2010); http://dx.doi.org/10.1063/1.3514170 (8 pages) | Cited 14 times

Online Publication Date: 6 December 2010

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Lead zirconate titanate (PbZr0.52Ti0.48O3−PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method. Single perovskite phase with (111)-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly (100)-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Significant differences between the macroscopic and microscopic electrical properties of the films were observed. Those differences can be assigned to changes in the nonswitching film-electrode layer and domain structure.
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77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.65.-j Piezoelectricity and electromechanical effects
77.55.H- Piezoelectric and electrostrictive films

Systematic study of the effect of La2O3 incorporation on the flatband voltage and Si band bending in the TiN/HfO2/SiO2/p-Si stack

Ming Di, Eric Bersch, Robert D. Clark, Steven Consiglio, Gert J. Leusink, and Alain C. Diebold

J. Appl. Phys. 108, 114107 (2010); http://dx.doi.org/10.1063/1.3516483 (7 pages) | Cited 5 times

Online Publication Date: 9 December 2010

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Recent studies have shown that La2O3 films can be used to adjust the threshold voltage (Vt) of NMOS Hf-based high-k/metal gate devices to desirable values, and a dipole at the high-k/SiO2 interface has been proposed to explain the Vt shifts. In order to investigate the mechanism of the Vt shift further, we have measured the flatband voltage (Vfb) and Si band bending of technologically relevant TiN/HfO2/La2O3/SiO2/p-Si stacks where the thickness and position of the La2O3 layer have been systematically varied. We observed systematic changes in Vfb, Si band bending and the HfO2-Si valence band offset as a function of La2O3 layer thickness and position. These changes can be explained by a band alignment model that includes a dipole at the high-k/SiO2 interface, thus supporting the work of previous authors. In addition, we have derived the theoretical relationship between Vfb and Si band bending, which agrees well with our experimental measurements.
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85.30.Tv Field effect devices

Microstructural and dielectric properties of Ba0.6Sr0.4Ti1−xZrxO3 based combinatorial thin film capacitors library

Guozhen Liu, Jérôme Wolfman, Cécile Autret-Lambert, Joe Sakai, Sylvain Roger, Monique Gervais, and François Gervais

J. Appl. Phys. 108, 114108 (2010); http://dx.doi.org/10.1063/1.3514153 (6 pages) | Cited 4 times

Online Publication Date: 9 December 2010

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Epitaxial growth of Ba0.6Sr0.4Ti1−xZrxO3 (0 ≤ x ≤ 0.3) composition spread thin film library on SrRuO3/SrTiO3 layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties.
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84.32.Tt Capacitors
81.16.Mk Laser-assisted deposition
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
77.22.Ch Permittivity (dielectric function)

Application of positron annihilation and Raman spectroscopies to the study of perovskite type materials

D. Grebennikov, O. Ovchar, A. Belous, and P. Mascher

J. Appl. Phys. 108, 114109 (2010); http://dx.doi.org/10.1063/1.3517098 (9 pages) | Cited 3 times

Online Publication Date: 10 December 2010

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Defect properties of perovskite type materials, Ba3B′Nb2O9 (where B′ = Mg, Zn, or Co), with near-stoichiometric compositions were studied by positron annihilation and Raman spectroscopies. Theoretical simulations of stoichiometric perovskites revealed a dependence of the positron bulk lifetime on the degree of ordering. In Ba3MgNb2O9 (BMN) the positron bulk lifetime for a completely disordered structure is 195 ps versus 237 ps for a completely ordered one. The predicted bulk lifetimes for Ba3ZnNb2O9 (BZN) and Ba3CoNb2O9 (BCN), with Pmmathm symmetries are 193 ps and 194 ps, respectively. It was found that deviation from stoichiometry results in the appearance of secondary Ba- and Nb-rich phases, which according to theoretical simulations have bulk lifetimes much longer than that of the host material. Positron lifetime spectroscopy was used to monitor changes in the concentration of these second phases. The difference between predicted defect lifetimes and the bulk values for the studied perovskites was less than 70 ps. This and the likely small concentrations made it impossible to discern the presence of point defects in the samples. Raman measurements demonstrated the presence of a particular mode that could be attributed to the formation of a 1:1 phase, the size of which is limited by requirements for charge compensation. The existence of an internal electric field between charged 1:1 nanoregions and the rest of material creates conditions for preferential positron annihilation that influence the obtained positron lifetime values. For BZN type materials it was found that the degree of 1:2 cation ordering decreases by increasing the sintering temperature to above 1400 °C.
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78.70.Bj Positron annihilation
78.30.Hv Other nonmetallic inorganics
81.40.Gh Other heat and thermomechanical treatments
61.72.J- Point defects and defect clusters

Multilevel resistive switching in Ti/CuxO/Pt memory devices

Sheng-Yu Wang, Chin-Wen Huang, Dai-Ying Lee, Tseung-Yuen Tseng, and Ting-Chang Chang

J. Appl. Phys. 108, 114110 (2010); http://dx.doi.org/10.1063/1.3518514 (6 pages) | Cited 15 times

Online Publication Date: 10 December 2010

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The multilevel resistive switching (RS) behaviors of the Ti/CuxO/Pt device were investigated by controlling the operated parameters of current and voltage bias in this study. We demonstrated that at least five-level memory states for data storage could be determined by controlling the current compliance, the span of voltage sweeping, and the amplitude of voltage pulse imposed on the memory device. During the dc voltage sweeping mode, not only the multilevel ON-states but also the multilevel OFF-states were achieved for the multilevel storage. The RS mechanism of the Ti/CuxO/Pt device is proposed to be related to the formation/rupture of the conducting filaments, arising from the interfacial oxygen ion migration between the Ti top electrode and CuxO films. Moreover, a possible conduction scenario for the multilevel RS behaviors is also suggested. Owing to all the multilevel memory states are distinguishable and possess the nondestructive readout property, it implies that the Ti/CuxO/Pt device has the promising potential for the future multilevel-capability memory cell application.
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84.30.Sk Pulse and digital circuits
85.30.Tv Field effect devices

Microstructure and ferroic properties of epitaxial [γ-Fe2O3–BiFeO3]−Bi3.25La0.75Ti3O12 composite bilayers

O. Gautreau, C. Harnagea, L. Gunawan, G. A. Botton, L. Pintilie, M. P. Singh, and A. Pignolet

J. Appl. Phys. 108, 114111 (2010); http://dx.doi.org/10.1063/1.3514591 (10 pages)

Online Publication Date: 10 December 2010

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Epitaxial [γ-Fe2O3–BiFeO3]/Bi3.25La0.75Ti3O12 and Bi3.25La0.75Ti3O12/[γ-Fe2O3–BiFeO3] composite bilayers were grown on SrRuO3 coated (111) SrTiO3 substrates in order to investigate the influence of the morphology of the γ-Fe2O3–BiFeO3 self assembled nanocomposite layer on the multiferroic properties of the bilayer. Both types of bilayers exhibit high resistivity and simultaneously ferroelectricity and ferrimagnetism at room temperature. When the γ-Fe2O3–BiFeO3 composite layer is sandwiched between the Bi3.25La0.75Ti3O12 film and the substrate, the BiFeO3 component is not only subjected to epitaxial strain induced by the surface on top of which it grows but also to elastic interactions with the Bi3.25La0.75Ti3O12 capping layer. The latter indeed reduce the amount of γ-Fe2O3 inclusions, affects the morphology of the grains in the γ-Fe2O3–BiFeO3 layer, and increases the shape anisotropy of the γ-Fe2O3 inclusions. Additionally, this modification in the microstructure of the γ-Fe2O3–BiFeO3 layer induces an imprint in the ferroelectric hysteresis loop as well as a decrease in the saturation magnetization, and its magnetic easy axis direction changes from in-plane to out-of plane.
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68.65.Ac Multilayers
68.60.Bs Mechanical and acoustical properties
77.55.Nv Multiferroic/magnetoelectric films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.Cd Fabrication of magnetic nanostructures
77.80.Dj Domain structure; hysteresis
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