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21 Dec 2009

Volume 95, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 251105 (2009); http://dx.doi.org/10.1063/1.3275666 (3 pages)

D. Stehr, C. M. Morris, D. Talbayev, M. Wagner, H. C. Kim, A. J. Taylor, H. Schneider, P. M. Petroff, and M. S. Sherwin
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Photoinduced change of dielectric permittivity in molecular doped polymer layer

Heisuke Sakai, Hideyuki Murata, Motonobu Murakami, Kei Ohkubo, and Shunichi Fukuzumi

Appl. Phys. Lett. 95, 252901 (2009); http://dx.doi.org/10.1063/1.3275800 (3 pages) | Cited 4 times

Online Publication Date: 21 December 2009

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We demonstrate a large photoinduced change of dielectric permittivity due to the charge separated (CS) state of an electron donor-acceptor linked molecule, 6-[4′-(N,N-diphenylamino)phenyl]-3-ethoxycarbonylcoumarin (DPA–CM), doped in a polymethylmethacryrate (PMMA) matrix. Dielectric permittivity of DPA–CM in PMMA film increases from 4.1 to 7.5 under photoirradiation. Electron spin resonance spectra of the films measured under photoirradiation clearly show the formation of the CS state of DPA–CM in PMMA matrix. The origin of the photoinduced change of the dielectric permittivity is ascribed to the realignment of dipole of the CS state of DPA–CM.
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77.22.Ch Permittivity (dielectric function)
68.55.am Polymers and organics
61.41.+e Polymers, elastomers, and plastics
77.55.-g Dielectric thin films
76.30.-v Electron paramagnetic resonance and relaxation
61.72.up Other materials

Ferroelectricity in glycine picrate: An astonishing observation in a centrosymmetric crystal

M. Shakir, B. K. Singh, B. Kumar, and G. Bhagavannarayana

Appl. Phys. Lett. 95, 252902 (2009); http://dx.doi.org/10.1063/1.3275714 (3 pages) | Cited 3 times

Online Publication Date: 22 December 2009

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Remarkable ferroelectric property has been observed in the glycine picrate single crystal though it crystallizes in centrosymmetric structure. An anomaly at 105 °C was observed in dielectric and ac conductivity measurements. The activation energies for conduction (Ea) below and above this temperature are found to be 0.31 and 0.53 eV, respectively. The remanant polarization (Pr) and coercive field (Ec) at room temperature were found to be 0.64 μC/cm2 and 6.22 kV/cm, respectively. However, a remarkable increase in these values was observed above 105 °C. A significantly high d33 (piezoelectric charge coefficient) in the order of 18 pC/N was observed.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Jd Polymers; organic compounds
61.66.Hq Organic compounds
72.80.Le Polymers; organic compounds (including organic semiconductors)
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants

Acoustic emission and dielectric studies of phase transitions within the morphotropic phase boundary of xPb(Zr1/2Ti1/2)O3-(1−x)Pb(Ni1/3Nb2/3)O3 relaxor ferroelectrics

E. Dul'kin, E. Mojaev, M. Roth, O. Khamman, and X. Tan

Appl. Phys. Lett. 95, 252903 (2009); http://dx.doi.org/10.1063/1.3275730 (3 pages) | Cited 2 times

Online Publication Date: 22 December 2009

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We have carried out a combined acoustic emission (AE) and dielectric permittivity study of the xPb(Zr1/2Ti1/2)O3-(1−x)Pb(Ni1/3Nb2/3)O3 relaxor ferroelectric ceramics with compositions x = 0.7–0.9 corresponding to its morphotropic phase boundary. Temperatures of all phase transitions occurring on heating are identified accurately by AE, and a direct transition between the low-temperature (rhombohedral) and high-temperature (pseudocubic) relaxor phases is found. The AE peak intensity is generally proportional to the temperature derivative of the dielectric permittivity, in agreement with a model proposed for a thermally cycled small elastic dipole.
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77.80.Jk Relaxor ferroelectrics
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
62.65.+k Acoustical properties of solids

Evidences for the depletion region induced by the polarization of ferroelectric semiconductors

Guo-Liang Yuan and Junling Wang

Appl. Phys. Lett. 95, 252904 (2009); http://dx.doi.org/10.1063/1.3268783 (3 pages) | Cited 9 times

Online Publication Date: 23 December 2009

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Ferroelectric materials possess spontaneous polarization pointing from negative to positive bound surface charges. When a ferroelectric semiconductor is polarized, the induced electric field can drive free carriers, e.g., electrons in an n-type material, to neutralize surface charges until such field becomes zero. Such diffusion of free carriers induces a depletion region. Polarization switch can move the depletion region to the opposite surface, thus it can be used to manipulate any properties that are affected by such depletion region, such as unidirectional current and photovoltaic current.
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77.22.Ej Polarization and depolarization
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Jc Other crystalline inorganic semiconductors
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