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16 Jan 2006

Volume 88, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 034101 (2006); http://dx.doi.org/10.1063/1.2164910 (3 pages)

W. K. Hensinger, S. Olmschenk, D. Stick, D. Hucul, M. Yeo, M. Acton, L. Deslauriers, C. Monroe, and J. Rabchuk
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Effect of thickness on the crystallization of ultrathin HfSiON gate dielectrics

G. Pant, A. Gnade, M. J. Kim, R. M. Wallace, B. E. Gnade, M. A. Quevedo-Lopez, and P. D. Kirsch

Appl. Phys. Lett. 88, 032901 (2006); http://dx.doi.org/10.1063/1.2165182 (3 pages) | Cited 26 times

Online Publication Date: 17 January 2006

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The crystallization of ultrathin hafnium silicon oxynitride (HfSiON) gate dielectric is studied as a function of physical thickness. Grazing incidence x-ray diffraction (GI-XRD) was used to detect phase separation and crystallization of 1.5, 2.0, 2.5, and 4.0 nm HfSiON films after 1000 °C 10 s dopant activation anneal. Crystallization peaks corresponding to monoclinic and tetragonal HfO2 were detected in 2.5 and 4.0 nm HfSiON films. These GI-XRD results were supported by plan-view transmission electron microscopy images of the HfSiON films. Film crystallinity seems to impact voltage instability in thicker HfSiON films.
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77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
61.72.Cc Kinetics of defect formation and annealing

Dielectric and photovoltaic phenomena in tungsten-doped Pb(Mg1/3Nb2/3)1−xTixO3 crystal

Chi-Shun Tu, F.-T. Wang, R. R. Chien, V. Hugo Schmidt, C.-M. Hung, and C.-T. Tseng

Appl. Phys. Lett. 88, 032902 (2006); http://dx.doi.org/10.1063/1.2165278 (3 pages) | Cited 6 times

Online Publication Date: 17 January 2006

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This work investigates dielectric and photovoltaic behaviors in Pb(Mg1/3Nb2/3)0.64Ti0.36O3 single crystal doped with 0.5 mol % WO3. Dielectric permittivities measured as functions of temperature and frequency reveal two first-order-type phase transitions upon heating and cooling. The photovoltaic response strongly depends on illumination wavelength, sample thickness, and prior electric-field poling. The relation of photovoltage and light intensity under near-ultraviolet (λ = 406 nm) illumination for the poled samples can be expressed by an exponential equation. Optical transmission reveals that the cutoff wavelength is near 400 nm and indicates a minimum electronic energy gap of ∼ 3.0 eV.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
72.40.+w Photoconduction and photovoltaic effects
77.22.Ej Polarization and depolarization
77.80.B- Phase transitions and Curie point
78.40.Ha Other nonmetallic inorganics

Realization of high-energy density polycrystalline piezoelectric ceramics

Rashed Adnan Islam and Shashank Priya

Appl. Phys. Lett. 88, 032903 (2006); http://dx.doi.org/10.1063/1.2166201 (3 pages) | Cited 21 times

Online Publication Date: 19 January 2006

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This letter reports a high energy density piezoelectric material in the system given as: Pb[(Zr0.52Ti0.48)O3]1−x[(Zn1/3Nb2/3)O3]x+yMnCO3, where x = 0.1 and y varies from 0.5 to 0.9 wt %. A piezoelectric material with high energy density is characterized by a high product of piezoelectric voltage constant (g) and piezoelectric strain constant (d). The condition for obtaining large magnitude of g constant was derived to be as ∣d∣ = εn, where ε is the permittivity of the material and n is constant having lower bound of 0.5. It was found that for all practical polycrystalline piezoelectric ceramic materials the magnitude of n lies in the range of 1.1–1.30 and as the magnitude of n decreases towards unity a giant enhancement in the magnitude of g was obtained. A two step sintering process was developed to optimize a polycrystalline ceramic composition with low magnitude of n. For the optimized composition the value of g33 and d33 was found to be 55.56×10−3 m2/C and 291×10−12 C/N, respectively, yielding the magnitude product d33∙g33 as ∼ 16168×10−15 m2/N which is significantly higher than the reported values in literature. The magnitude of n for this composition was calculated to be 1.151. This material is extremely promising for immediate applications in the sensing and energy harvesting.
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77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.22.Ch Permittivity (dielectric function)
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Engineering domain configurations for enhanced piezoelectricity in barium titanate single crystals

J. J. Liu, Y. C. Zhou, A. K. Soh, and J. Y. Li

Appl. Phys. Lett. 88, 032904 (2006); http://dx.doi.org/10.1063/1.2166480 (3 pages) | Cited 13 times

Online Publication Date: 20 January 2006

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In this letter, we propose a mechanism for enhanced piezoelectricity that takes advantage of both intrinsic crystalline anisotropy of ferroelectric crystal and extrinsic 90° domain switching of ferroelectric variant. The domain configurations we consider here are not clamped, and thus allow domain switching driven by the competition between external electric field and internal depolarization field. The intrinsic and extrinsic piezoelectric responses of barium titanate single crystals under different crystallographic orientations are calculated using an energy minimization theory, where it is observed that the piezoelectric coefficient is significantly enhanced by the 90° domain switching, especially under the small field measurement where the domain wall movement is reversible, which is consistent with recent experimental observations. The optimal crystallographic orientation is also identified.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Nucleation and growth of periodic domains during electric field poling in flux-grown KTiOPO4 observed by atomic force microscopy

C. Canalias, S. Wang, V. Pasiskevicius, and F. Laurell

Appl. Phys. Lett. 88, 032905 (2006); http://dx.doi.org/10.1063/1.2166678 (3 pages) | Cited 8 times

Online Publication Date: 20 January 2006

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The domain structure of periodically poled KTiOPO4 crystals were studied on both the polar and nonpolar faces utilizing a voltage-modulated atomic force microscope. The measurements give information of domain nucleation, growth, and merging. Two different kind of overpoling behaviors have been observed depending on the magnitude of the applied field.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis

Structural and electrical evolution of gate dielectric breakdown observed by conductive atomic force microscopy

Li Zhang and Yuichiro Mitani

Appl. Phys. Lett. 88, 032906 (2006); http://dx.doi.org/10.1063/1.2166679 (3 pages) | Cited 13 times

Online Publication Date: 20 January 2006

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To clarify the breakdown (BD) mechanism in the gate oxide of transistors, BD evolution from prebreakdown (pre-BD) stage to BD transient is investigated by conductive atomic force microscopy. High electric fields of both polarities are applied to induce pre-BD degradation. Structural hillocks are observed to be dependent on stress polarity. The height of hillocks increases with BD evolution while keeping a similar lateral size. Flatband shift caused by negative charge is observed independent of stress polarity. Lateral size of the electrical degradation is similar to that of the hillock throughout BD evolution. We attribute the hillocks to deformation of Si substrate at the pre-BD stage, where an electrothermal effect plays an important role.
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77.22.Jp Dielectric breakdown and space-charge effects
72.20.Pa Thermoelectric and thermomagnetic effects
68.37.Ps Atomic force microscopy (AFM)
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Nucleation of atomic-layer-deposited HfO2 films, and evolution of their microstructure, studied by grazing incidence small angle x-ray scattering using synchrotron radiation

M. L. Green, A. J. Allen, X. Li, J. Wang, J. Ilavsky, A. Delabie, R. L. Puurunen, and B. Brijs

Appl. Phys. Lett. 88, 032907 (2006); http://dx.doi.org/10.1063/1.2164417 (3 pages) | Cited 8 times

Online Publication Date: 20 January 2006

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We report the results of grazing incidence small angle x-ray scattering experiments on the nucleation and growth of atomic layer deposited HfO2 films. The scattering features are internal (porosity) and external (roughness) surfaces. Films grown on H-terminated Si exhibit greater scattering than films grown on chemically oxidized Si. The films grown on H-terminated Si may be as much as 50% porous. Characteristic scattering feature sizes are those of the film nuclei, about 2 nm, which then coalesce and become inherited features of the films. Films grown on chemically oxidized Si are observed to coalesce at about 25 growth cycles.
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81.05.Rm Porous materials; granular materials
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.70.Ck X-ray scattering
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