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25 Sep 2006

Volume 89, Issue 13, Articles (13xxxx)

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Appl. Phys. Lett. 89, 131108 (2006); http://dx.doi.org/10.1063/1.2356892 (3 pages)

Paul E. Barclay, Kartik Srinivasan, Oskar Painter, Benjamin Lev, and Hideo Mabuchi
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Electrical response of a liquid crystal cell: The role of Debye’s layer

G. Barbero, G. Cipparrone, O. G. Martins, P. Pagliusi, and A. M. Figueiredo Neto

Appl. Phys. Lett. 89, 132901 (2006); http://dx.doi.org/10.1063/1.2357554 (3 pages) | Cited 4 times

Online Publication Date: 25 September 2006

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The authors investigate the effect of the surface treatment on the electrical response of a nematic liquid crystal cell. The theoretical analysis is performed by describing, from the electrical point of view, the liquid crystal and the surface treatment by means of the dielectric constants and the electrical conductivities. The predictions of the model are compared with the measurements performed on a nematic cell submitted to an external voltage steplike or linear in time. They show that to correctly interpret the experimental data it is necessary to take into account the surface layer of Debye, connected with the presence of the ions, responsible for the electrical conduction in nematics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions
81.65.-b Surface treatments
77.22.Ch Permittivity (dielectric function)
72.80.Le Polymers; organic compounds (including organic semiconductors)

Highly controlled orientation of CaBi4Ti4O15 using a strong magnetic field

Tohru S. Suzuki, Masahiko Kimura, Kosuke Shiratsuyu, Akira Ando, Yoshio Sakka, and Yukio Sakabe

Appl. Phys. Lett. 89, 132902 (2006); http://dx.doi.org/10.1063/1.2357868 (3 pages) | Cited 6 times

Online Publication Date: 26 September 2006

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The texture of feeble magnetic ceramics can be controlled by a strong magnetic field. When the magnetic susceptibility of the c axis is smaller than that of the other axes, the c axis aligns perpendicular to the magnetic field; however, the direction is randomly oriented on the plane perpendicular to the magnetic field. The authors demonstrate in this letter that a highly controlled texture in bismuth titanate, which has a c-axis susceptibility smaller than the other axes, can be achieved using a two-step magnetic field procedure. This highly controlled orientation is effective for improving the electromechanical coupling coefficient.
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75.50.Dd Nonmetallic ferromagnetic materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity
75.30.Cr Saturation moments and magnetic susceptibilities
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)

Impact of film properties of atomic layer deposited HfO2 resulting from annealing with a TiN capping layer

D. H. Triyoso, P. J. Tobin, B. E. White, R. Gregory, and X. D. Wang

Appl. Phys. Lett. 89, 132903 (2006); http://dx.doi.org/10.1063/1.2357032 (3 pages) | Cited 14 times

Online Publication Date: 27 September 2006

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Atomic layer deposited HfO2 films void and exhibit poor electrical characteristics when annealed at high temperature unless a TiN capping layer is used. The TiN is removed prior to characterization of the dielectric. The authors find that capped HfO2 films annealed at 1000 °C by rapid thermal process are smooth and void-free. The microstructure of HfO2 is modified from fully monoclinic to a mixed monoclinic and tetragonal phase when the capping layer is used. Conducting atomic force microscopy performed on these films shows fewer areas with high leakage current. Mo/HfO2 capacitors show improved CV characteristics and lower leakage current density.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology

Atomic rearrangements in HfO2/Si1−xGex interfaces

Deok-Yong Cho, S.-J. Oh, Tae Joo Park, and Cheol Seong Hwang

Appl. Phys. Lett. 89, 132904 (2006); http://dx.doi.org/10.1063/1.2357341 (3 pages) | Cited 5 times

Online Publication Date: 27 September 2006

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Atomic exchanges across the interface between a HfO2 thin film and strained semiconducting Si1−xGex (x = 0.1, 0.2, and 0.3) was investigated by extended x-ray absorption fine structures. Atomic layer deposition of HfO2 films on epitaxial Si1−xGex produces a Hf-silicate (Hf–O–Si bond) phase at the interface. Also O atoms diffuse into the Si1−xGex alloy to form Ge oxide in a segregated phase. This tendency becomes evident when the Ge concentration of the substrate becomes higher or when HfO2 is deposited and these samples are compared to the pure Si1−xGex substrates which have been exposed to ambient atmosphere.
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68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
66.30.Ny Chemical interdiffusion; diffusion barriers
78.70.Dm X-ray absorption spectra
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films

Surface potential imaging of nanoscale LiNbO3 domains investigated by electrostatic force microscopy

Xiaoyan Liu, Kenji Kitamura, and Kazuya Terabe

Appl. Phys. Lett. 89, 132905 (2006); http://dx.doi.org/10.1063/1.2358115 (3 pages) | Cited 13 times

Online Publication Date: 28 September 2006

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The surface potential imaging of nanoscale domains engineered on near-stoichiometric LiNbO3 (SLN) crystals was investigated using Kelvin probe-based, electrostatic force microscopy. The surface potential image reflected in the domain structure was clearly obtained using heat treatment in vacuum due to the decreases in spontaneous polarization and screening charge adsorption. In-vacuum observation revealed that the surface potential contrast and polarity of nanoscale engineered domains can be repeatedly changed by switching the temperature between 298 and 393 K, demonstrating the controllability of the spontaneous polarization distribution in SLN crystals.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
68.37.-d Microscopy of surfaces, interfaces, and thin films
61.66.Bi Elemental solids
61.66.Dk Alloys
81.40.Gh Other heat and thermomechanical treatments
77.22.Ej Polarization and depolarization

Dielectric and piezoelectric properties of hydroxyapatite-BaTiO3 composites

C. R. Bowen, J. Gittings, I. G. Turner, F. Baxter, and J. B. Chaudhuri

Appl. Phys. Lett. 89, 132906 (2006); http://dx.doi.org/10.1063/1.2355458 (3 pages) | Cited 16 times

Online Publication Date: 28 September 2006

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This letter describes the relationships between the composition and the dielectric and piezoelectric properties of hydroxyapatite-barium titanate composites for polarized bone substitutes. The ac conductivity and permittivity were characterized from 0.1 Hz to 1 MHz, along with measurements of the d33 piezoelectric charge coefficient. The addition of BaTiO3 led to an increase in permittivity and ac conductivity of the material. The increase in both properties was attributed to the presence of the high permittivity ferroelectric phase. The d33 and g33 coefficients decreased rapidly as hydroxyapatite was introduced into BaTiO3 material. Composites below 80% by volume of BaTiO3 exhibited no net piezoelectric effect.
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87.85.J- Biomaterials
77.84.Lf Composite materials
77.65.-j Piezoelectricity and electromechanical effects
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity

Enhanced tetragonality in (x)PbTiO3–(1−x)Bi(B′B″)O3 systems: Bi(Zn3/4W1/4)O3

David M. Stein, Matthew R. Suchomel, and Peter K. Davies

Appl. Phys. Lett. 89, 132907 (2006); http://dx.doi.org/10.1063/1.2357871 (3 pages) | Cited 20 times

Online Publication Date: 28 September 2006

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Solid solutions in the (x)PbTiO3–(1−x)Bi(Zn3/4W1/4)O3 system have been examined by x-ray diffraction, dielectric measurements, and thermal analysis. Bi(Zn3/4W1/4)O3 increases the tetragonality and Curie temperature of PbTiO3 which reach a value of 1.08 and 530 °C, respectively, at the limit of the single-phase perovskite forming region (x ∼ 0.8). The observation of a sustained increase in the tetragonality in this system is similar to the behavior of the (x)PbTiO3–(1−x)Bi(Zn1/2Ti1/2)O3 system and highlights the unique properties of Bi-based systems when the B sites contain high concentrations of highly polarizable cations.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.-j Piezoelectricity and electromechanical effects
77.80.B- Phase transitions and Curie point
61.66.Fn Inorganic compounds
77.22.Ej Polarization and depolarization

Dielectric properties of Bi1.5Zn1.0Nb1.5O7/Mn-doped Ba0.6Sr0.4TiO3 heterolayered films grown by pulsed laser deposition

Wangyang Fu, Lingzhu Cao, Shufang Wang, Zhihui Sun, Bolin Cheng, Qian Wang, and Hong Wang

Appl. Phys. Lett. 89, 132908 (2006); http://dx.doi.org/10.1063/1.2354013 (3 pages) | Cited 12 times

Online Publication Date: 28 September 2006

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Bi1.5Zn1.0Nb1.5O7/Mn-doped Ba0.6Sr0.4TiO3 heterolayered films have been deposited on (111) Nb:SrTiO3 substrate by pulsed laser deposition. The heterolayered films were found to possess a medium permittivity around 200, a low loss tangent of 0.0025, and a relatively high tunability up to 25% measured with dc bias field of 850 kV/cm. The authors analyzed the bias field dependent permittivity of the heterolayered films using layer model. Based on the analysis, a structure with the tunability as high as 40% under a bias field of 420 kV/cm was suggested after optimizing the thickness of the component layers.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
68.65.Ac Multilayers
81.15.Fg Pulsed laser ablation deposition

Compositional grading effects on permittivity temperature stability in (Ba,Sr)TiO3 films

J. Sigman, P. G. Clem, and C. D. Nordquist

Appl. Phys. Lett. 89, 132909 (2006); http://dx.doi.org/10.1063/1.2357934 (3 pages) | Cited 7 times

Online Publication Date: 28 September 2006

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Compositionally graded (BaxSr1−x)TiO3 films are deposited on Pt/Ti/SiO2/Si via chemical solution deposition to investigate permittivity temperature stability improvement. Dielectric responses and temperature coefficients of capacitance (TCCs) are monitored as function of the grading sequence and direction. Downgraded (decreasing Ba/Sr ratio with film thickness) films universally display the lowest TCC values. BaTiO3-rich films display finer grain sizes which appear to be propagated into overlying layers, apparently suppressing ferroelectric character. By applying this microstructure effect, properties may be tailored to develop more temperature-stable capacitor elements for microwave devices.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity

Effects of BaTiO3 on dielectric behavior of BaTiO3–Ni–polymethyl methacrylate composites

Hyung-Woo Choi, Young-Woo Heo, Joon-Hyung Lee, Jeong-Joo Kim, Hee-Young Lee, Eun-Tae Park, and Yul-Kyo Chung

Appl. Phys. Lett. 89, 132910 (2006); http://dx.doi.org/10.1063/1.2354425 (3 pages) | Cited 24 times

Online Publication Date: 29 September 2006

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Effects of ferroelectric BaTiO3 particles were investigated on the dielectric behavior of BaTiO3–Ni–polymethyl methacrylate composites fabricated by a two-step mixing and hot-molding method. The percolation power law in the smearing region was employed to explain the experimental results. The composites exhibit the dependence of the dielectric constant, dielectric loss, and percolation threshold on the concentration and particle size of BaTiO3. The results suggest that BaTiO3 particles play an important role in increasing the percolation threshold and the smearing region as well as the dielectric constant of BaTiO3–Ni–polymethyl methacrylate composites.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Jd Polymers; organic compounds

Tunable dielectric properties of lead barium zirconate niobate films

Ya-Ling Kuo and Jenn-Ming Wu

Appl. Phys. Lett. 89, 132911 (2006); http://dx.doi.org/10.1063/1.2357851 (3 pages) | Cited 2 times

Online Publication Date: 29 September 2006

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The effect of substitution of niobium for zirconium on tunable behavior of lead barium zirconate (PBZ) films was investigated. Lead barium zirconate niobate films were grown on Pt/Ti/SiO2/Si substrates using chemical solution deposition method. The substitution of Nb for Zr enhances tunable properties of PBZ films. The dielectric tunabilities are excellent, all higher than 45% with a maximum = 60%. The substitution of Nb for Zr raises values of figure of merit (FOM) of films. The maximum FOM takes place at 5 mol % Nb with a value of 90, which is about three times that of the corresponding PBZ film.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)

High-resolution piezoresponse force microscopy investigation of imprint in ferroelectric thin films

V. Anbusathaiah, V. Nagarajan, and S. Aggarwal

Appl. Phys. Lett. 89, 132912 (2006); http://dx.doi.org/10.1063/1.2357894 (3 pages) | Cited 5 times

Online Publication Date: 29 September 2006

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High-resolution piezoresponse force microscopy is used to visualize imprint in polycrystalline PbZr0.25Ti0.75O3 thin films. Three-dimensional domain images show the formation of a thin bright band ( ∼ 8 nm in width) running along the grain boundary after local application of a negative bias. Such bands extend completely over the region under local bias thereby forming networks. Cross-section profile analysis reveals that these are not pinned regions, rather they are formed during the switching process. This demonstrates an active role of grain boundaries in pinning a preferential polarization state. Piezoresponse hysteresis loops confirm that these regions are imprinted.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
61.72.Mm Grain and twin boundaries

Multiferroic epitaxial Pb(Fe1/2Nb1/2)O3 thin films: A relaxor ferroelectric/weak ferromagnet with a variable structure

Li Yan, Jiefang Li, Carlos Suchicital, and D. Viehland

Appl. Phys. Lett. 89, 132913 (2006); http://dx.doi.org/10.1063/1.2357926 (3 pages) | Cited 10 times

Online Publication Date: 29 September 2006

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The authors report the structural, ferroelectric, and ferromagnetic properties of Pb(Fe1/2Nb1/2)O3 epitaxial thin layers grown on (001), (110), and (111) SrTiO3 substrates by pulsed-laser deposition; films were of sufficient resistivity to enable high-field P-E measurements. Findings are as follows: epitaxial strain results in (i) a dramatic increase in the spontaneous polarization Ps; (ii) a lattice structure that is dependent on substrate orientation; (iii) a slim-loop P-E response and relaxor ferroelectric characteristics in the dielectric constant, both of which are nearly independent of crystallographic orientation; and (iv) a weak ferromagnetic moment, which is dependent on epitaxial mismatch.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
75.50.Dd Nonmetallic ferromagnetic materials
77.55.-g Dielectric thin films
75.70.Ak Magnetic properties of monolayers and thin films
77.80.-e Ferroelectricity and antiferroelectricity
75.30.Cr Saturation moments and magnetic susceptibilities
77.22.Ch Permittivity (dielectric function)
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