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14 Feb 2011

Volume 98, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 073101 (2011); http://dx.doi.org/10.1063/1.3554360 (3 pages)

Wei Xu, Rajesh Leeladhar, Yao-Tsan Tsai, Eui-Hyeok Yang, and Chang-Hwan Choi
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Enhanced multiferroic properties of single-phase BiFeO3 bulk ceramics by Ho doping

Nari Jeon, Dibyaranjan Rout, Ill Won Kim, and Suk-Joong L. Kang

Appl. Phys. Lett. 98, 072901 (2011); http://dx.doi.org/10.1063/1.3552682 (3 pages) | Cited 21 times

Online Publication Date: 14 February 2011

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Dense single-phase BiFeO3 and Bi0.9Ho0.1FeO3 ceramics were prepared by the solid-state reaction method. With Ho doping, the remnant polarization of BiFeO3 was enhanced and the switching characteristics improved at low electric fields. Ho doping increased the breakdown voltage with a reduction of the leakage current while mitigating the remnant polarization at high electric fields. These results can explain conflicting findings regarding the effects of rare-earth doping on remnant polarization. Bi0.9Ho0.1FeO3 exhibited peculiar double hysteresis looplike magnetization-magnetic field curves with a much enhanced remnant magnetization. These improved properties obtained by Ho doping demonstrate the possibility of enhancing the multiferroic applicability of BiFeO3.
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81.20.-n Methods of materials synthesis and materials processing
77.80.Fm Switching phenomena
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Grain boundary assisted degradation and breakdown study in cerium oxide gate dielectric using scanning tunneling microscopy

K. Shubhakar, K. L. Pey, S. S. Kushvaha, S. J. O’Shea, N. Raghavan, M. Bosman, M. Kouda, K. Kakushima, and H. Iwai

Appl. Phys. Lett. 98, 072902 (2011); http://dx.doi.org/10.1063/1.3553190 (3 pages) | Cited 5 times

Online Publication Date: 14 February 2011

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The presence of grain boundaries (GBs) in polycrystalline high-κ (HK) gate dielectric materials affects the electrical performance and reliability of advanced HK based metal-oxide-semiconductor devices. It is important to study the role of GB in stress-induced-leakage current (SILC) degradation and time-dependent dielectric breakdown of polycrystalline HK gate stacks. In this work, we present nanoscale localized electrical study and uniform stressing analysis comparing the electrical conduction properties at grain and GB locations for blanket cerium oxide (CeO2)-based HK thin films using scanning tunneling microscopy. The results clearly reveal higher SILC degradation rate at GB sites and their vulnerability to early percolation, supporting the phenomenon of GB-assisted HK gate dielectric degradation and breakdown.
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73.61.Ng Insulators
77.55.df For silicon electronics
61.72.Mm Grain and twin boundaries

Magnetodielectric response of square-coordinated MnO2 unit in cubic BiMn7O12

N. Imamura, K. Singh, D. Pelloquin, Ch. Simon, T. Sasagawa, M. Karppinen, H. Yamauchi, and A. Maignan

Appl. Phys. Lett. 98, 072903 (2011); http://dx.doi.org/10.1063/1.3551540 (3 pages) | Cited 1 time

Online Publication Date: 14 February 2011

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The magnetodielectric (MD) effect for BiMn7O12 with the cubic A′A″3B4O12-type A-site-ordered perovskite structure has been investigated. A clear negative MD response around and beyond TN has been observed and attributed to antiferromagnetic spin fluctuations. With further decreasing temperature (T⪡TN) a switching to a complex positive MD effect is found confirming additional contribution coming from the magnetic ordering. The present study underlines the importance of square-coordinated MnA″O2 units for generating MD coupling in an A′A″3B4O12-type structure; the magnitude of the MD effect then strongly depends on the precise chemical composition.
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75.85.+t Magnetoelectric effects, multiferroics
75.60.Lr Magnetic aftereffects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Ee Antiferromagnetics

On the origin of time-temperature superposition in disordered solids

I. Sakellis

Appl. Phys. Lett. 98, 072904 (2011); http://dx.doi.org/10.1063/1.3543634 (3 pages) | Cited 2 times

Online Publication Date: 15 February 2011

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In this paper by employing various experimental facts for different classes of materials, two critical conditions are derived, which lead to the empirically used scaling relations describing the ac response of disordered nonmetals. In parallel the origin of time-temperature superposition is explored while the scenario of time-pressure (or /temperature) superposition is introduced. Moreover, a unified equation for the entire frequency range of ac conductivity is proposed. The results are physically visualized within the frame of percolation theory, attempting to establish a link to the dominant approaches of Hunt [Philos. Mag. B 81, 875 (2001)] and Dyre [J. Appl. Phys. 64, 2456 (1988)] .
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61.43.-j Disordered solids
77.22.Ch Permittivity (dielectric function)

Electric field concentration in the vicinity of the interface between anode and degraded BaTiO3-based ceramics in multilayer ceramic capacitor

Takafumi Okamoto, Shuji Kitagawa, Noriyuki Inoue, and Akira Ando

Appl. Phys. Lett. 98, 072905 (2011); http://dx.doi.org/10.1063/1.3555466 (3 pages) | Cited 2 times

Online Publication Date: 15 February 2011

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The electric field distribution of degraded dielectric layers in multilayer ceramic capacitors (MLCCs) was investigated by Kelvin probe force microscopy (KFM) to clarify the insulation degradation mechanism in MLCCs. For the degraded dielectric layers, the electric field was found to be concentrated near the anodes. This concentration easily moved to the opposite side with a reversal of the applied voltage of 5 V (13 kV/cm) during KFM measurement at room temperature. On the other hand, electric field concentrations and electric field distributions did not change in fresh MLCCs, indicating that the electric field concentrations easily transfer near higher-potential interfaces between electrodes and ceramics only in degraded MLCCs. These facts suggest that Schottky barriers would be formed in degraded MLCCs. The KFM technique discussed in this work is a very useful tool for measuring the surface potential and helps clarify the local electric field concentration near the electrodes.
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84.32.Tt Capacitors
73.30.+y Surface double layers, Schottky barriers, and work functions

The electromagnetic property of chemically reduced graphene oxide and its application as microwave absorbing material

Chao Wang, Xijiang Han, Ping Xu, Xiaolin Zhang, Yunchen Du, Surong Hu, Jingyu Wang, and Xiaohong Wang

Appl. Phys. Lett. 98, 072906 (2011); http://dx.doi.org/10.1063/1.3555436 (3 pages) | Cited 23 times

Online Publication Date: 18 February 2011

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The residual defects and groups in chemically reduced graphene oxide cannot only improve the impedance match characteristic and prompt energy transition from contiguous states to Fermi level, but also introduce defect polarization relaxation and groups’ electronic dipole relaxation, which are all in favor of electromagnetic wave penetration and absorption. The chemically reduced graphene oxide shows enhanced microwave absorption compared with graphite and carbon nanotubes, and can be expected to display better absorption than high quality graphene, exhibiting a promising prospect as microwave absorbing material.
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77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.22.Pr Electronic structure of graphene
84.40.-x Radiowave and microwave (including millimeter wave) technology

Position of defects with respect to domain walls in Fe3+-doped Pb[Zr0.52Ti0.48]O3 piezoelectric ceramics

Peter Jakes, Emre Erdem, Rüdiger-A. Eichel, Li Jin, and Dragan Damjanovic

Appl. Phys. Lett. 98, 072907 (2011); http://dx.doi.org/10.1063/1.3555465 (3 pages) | Cited 7 times

Online Publication Date: 18 February 2011

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The position of (FeZr,Ti′−VO••)• defect complexes in Pb[Zr0.52Ti0.48]O3 (PZT) piezoelectric ceramics was investigated by means of electron paramagnetic resonance (EPR) spectroscopy. The method of analysis pursued to obtain information on the (FeZr,Ti′−VO••)• position is to compare the EPR spectra of Fe3+-doped PZT specimen at different states, i.e., a powder that is representative for a system with considerably reduced amount of non-180° domain walls and a sintered ceramic of identical composition but with markedly developed domain structure. By considering the local site symmetry for the Fe3+-functional center, indirect evidence is obtained that the (FeZr,Ti′−VO••)• defect complexes are located within domains and not at domain walls.
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61.72.-y Defects and impurities in crystals; microstructure
76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)
77.65.-j Piezoelectricity and electromechanical effects
77.80.Dj Domain structure; hysteresis

Nonlinear dielectric properties of (Bi0.5Na0.5)TiO3-based lead-free piezoelectric thick films

Haibo Zhang, Shenglin Jiang, and Koji Kajiyoshi

Appl. Phys. Lett. 98, 072908 (2011); http://dx.doi.org/10.1063/1.3557525 (3 pages)

Online Publication Date: 18 February 2011

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The effects of applied dc bias field, temperature, frequency, and doping types on the nonlinear dielectric behaviors of Bi0.5(Na0.82K0.18)0.5TiO3 piezoelectric films with thickness of 40 μm have been investigated. It is demonstrated that the dielectric permittivity versus ac field amplitude departed from linearity at high temperature, which is caused by a decrease of the coercive field with increasing temperature. The frequency dependence of the dielectric permittivity is related to domain wall pinning. The thicker piezoelectric films exhibit higher extrinsic contribution due to high domain wall mobility and less domain wall pinning, resulting from the increased grain size and film thickness.
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77.55.hn Other piezoelectric or electrostrictive films
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.84.Cg PZT ceramics and other titanates
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