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16 Aug 2010

Volume 97, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 073101 (2010); http://dx.doi.org/10.1063/1.3478515 (3 pages)

Hon-Way Lin (林弘偉), Yu-Jung Lu (呂宥蓉), Hung-Ying Chen (陳虹穎), Hong-Mao Lee (李弘貿), and Shangjr Gwo (果尚志)
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Surface potential due to charge accumulation during vacuum ultraviolet exposure for high-k and low-k dielectrics

H. Ren, H. Sinha, A. Sehgal, M. T. Nichols, G. A. Antonelli, Y. Nishi, and J. L. Shohet

Appl. Phys. Lett. 97, 072901 (2010); http://dx.doi.org/10.1063/1.3481079 (3 pages) | Cited 6 times

Online Publication Date: 16 August 2010

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The surface potential due to charge accumulation during vacuum ultraviolet irradiation of high-k and low-k thin dielectric films is measured. Measurement of the substrate current, which is the sum of the charge-accumulation and photoinjection currents, allows an in situ monitoring of the charge accumulation during irradiation. The relationship between the substrate current and the calculated in situ surface potential is also found, eliminating the need for a separate surface-potential measurement. With a high photon dose, the surface potential and substrate current reach a steady-state value with no further net charge accumulation.
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77.55.Bh Low-permittivity dielectric films
77.55.D- High-permittivity gate dielectric films
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Enhanced ferroelectric properties in Mn-doped K0.5Na0.5NbO3 thin films derived from chemical solution deposition

Lingyan Wang, Wei Ren, Peng Shi, Xiaofeng Chen, Xiaoqing Wu, and Xi Yao

Appl. Phys. Lett. 97, 072902 (2010); http://dx.doi.org/10.1063/1.3479530 (3 pages) | Cited 12 times

Online Publication Date: 16 August 2010

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Mn-doped K0.5Na0.5NbO3 (KNN) thin films derived from chemical solution deposition have been investigated. 2 mol % manganese acetate was introduced into the polyvinylpyrrolidone-modified KNN precursor solution to prepare the KNN thin films. It was found that Mn doping can increase the dielectric constant and decrease the dielectric loss, as well as significantly decrease the leakage current. The leakage current density of Mn-doped KNN film is about 3×10−6 A/cm2 at an electric field of 50 kV/cm, which is 104 times lower than that of the undoped film (about 3×10−2 A/cm2). These are attributed to the decrease in the concentration in oxygen vacancies and free carrier-holes by increasing the valence of Mn during thermal treatment. As a result, well saturated polarization-electric field hysteresis loops were obtained in the Mn-doped KNN thin films.
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77.80.Dj Domain structure; hysteresis
61.72.jd Vacancies
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)

Dissimilarity of polar displacements in barium and lead based relaxors

D. Phelan, J. N. Millican, and P. M. Gehring

Appl. Phys. Lett. 97, 072903 (2010); http://dx.doi.org/10.1063/1.3479524 (3 pages) | Cited 1 time

Online Publication Date: 19 August 2010

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Powder neutron diffraction experiments were performed on the relaxor compound, Ba(Zn1/3Nb2/3)0.95Ti0.05O3, which was recently shown to have stronger frequency dependence in its permittivity than many Pb-based relaxors (PBR), such as PbMg1/3Nb2/3O3 [ L. Khemakhem et al., J. Alloys Compd. 452, 451 (2008)] . Several notable differences in structural properties were observed in the present measurements compared to PBR. In particular, much smaller atomic displacement parameters were found, especially on the A (Ba) site, which indicates that the local shifts of the Ba atoms are much smaller than the Pb shifts in PBR. Moreover, no signature of electrostrictive strain is apparent in the thermal expansion, and instead the thermal expansion is much larger at low temperatures than for PBR.
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77.80.Jk Relaxor ferroelectrics
77.84.Cg PZT ceramics and other titanates
77.84.Ek Niobates and tantalates
77.22.Ch Permittivity (dielectric function)
61.66.Fn Inorganic compounds
65.40.De Thermal expansion; thermomechanical effects

Electromechanical response of porous piezoelectric materials: Effects of porosity connectivity

Sumantu Iyer and T. A. Venkatesh

Appl. Phys. Lett. 97, 072904 (2010); http://dx.doi.org/10.1063/1.3481416 (3 pages) | Cited 5 times

Online Publication Date: 19 August 2010

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A three-dimensional finite element model is developed to completely characterize the electromechanical response of a general piezoelectric material with spherical or cylindrical porosity, respectively, with zero-dimensional (3–0) or one-dimensional (3–1) connectivity and to obtain a quantitative assessment of the effects of porosity connectivity on the effective performance characteristics of porous piezoelectric materials. By considering materials with different crystal symmetries, it is demonstrated that piezoelectric materials designed with spherical porosity (with 3–0 connectivity) exhibit enhanced hydrostatic figure of merit and are more suitable for hydrophone applications, as compared to materials engineered with cylindrical porosity (with 3–1 connectivity).
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77.65.-j Piezoelectricity and electromechanical effects
61.43.Gt Powders, porous materials
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Polarization from dielectric-barrier discharges in ferroelectrets: Mapping of the electric-field profiles by means of thermal-pulse tomography

Xunlin Qiu, Lars Holländer, Rosaura Flores Suárez, Werner Wirges, and Reimund Gerhard

Appl. Phys. Lett. 97, 072905 (2010); http://dx.doi.org/10.1063/1.3481802 (3 pages) | Cited 1 time

Online Publication Date: 20 August 2010

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A polymer-ferroelectret system is fabricated by attaching two uniform polycarbonate films to a grid produced from double-sided adhesive tape by means of computer-controlled laser cutting. The openings of the grid structure result in well-defined voids inside the three-layer system, which can be internally charged through dielectric barrier discharges. The negatively charged internal void surfaces can be made visible by means of xerographical toner, and the electric-field distribution inside such ferroelectrets can be studied with thermal-pulse tomography. Both techniques exhibit polarization patterns that are consistent with the grid structure. Possible reasons for the observed non-uniform charge distributions are discussed.
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52.80.-s Electric discharges
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.41.+e Polymers, elastomers, and plastics
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