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4 Dec 2006

Volume 89, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 89, 233120 (2006); http://dx.doi.org/10.1063/1.2402115 (3 pages)

S. Yeo, Y. Horibe, S. Mori, C. M. Tseng, C. H. Chen, A. G. Khachaturyan, C. L. Zhang, and S.-W. Cheong
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Nonlinear properties of thin ferroelectric film-based capacitors at elevated microwave power

Oleg Soldatenkov, Tatyana Samoilova, Andrey Ivanov, Andrey Kozyrev, David Ginley, and Tatyana Kaydanova

Appl. Phys. Lett. 89, 232901 (2006); http://dx.doi.org/10.1063/1.2399336 (3 pages)

Online Publication Date: 4 December 2006

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A key interest in high power high frequency microwave devices is their performance at high power levels. The authors discuss two mechanisms determining the capacitance variations of a thin ferroelectric film-based nonlinear capacitor under elevated microwave power levels analytically and experimentally studied over wide frequency range. The mechanisms are the dielectric nonlinearity under the microwave electric field and ferroelectric film heating due to microwave energy dissipation. It is shown that for thin ferroelectric film parallel plate capacitive structures up to millimeter-wave frequency range, the electric field effect is the dominant mechanism in the capacitance variations, and for limitations on power handling.
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84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.40.-x Radiowave and microwave (including millimeter wave) technology

Dysprosium scandate thin films as an alternate amorphous gate oxide prepared by metal-organic chemical vapor deposition

Reji Thomas, Peter Ehrhart, Martina Luysberg, Markus Boese, Rainer Waser, Martin Roeckerath, Eduard Rije, Juergen Schubert, Sven Van Elshocht, and Matty Caymax

Appl. Phys. Lett. 89, 232902 (2006); http://dx.doi.org/10.1063/1.2402121 (3 pages) | Cited 28 times

Online Publication Date: 5 December 2006

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Dysprosium scandate (DyScO3) thin films were deposited on Si substrates using metal-organic chemical vapor deposition. Individual source precursors of Dy and Sc were used and deposition temperatures ranged from 480 to 700 °C. Films were amorphous with low root mean square roughness ( ⩽ 2 Å) and were stable up to 1050 °C annealing. Electrical characterization yielded C-V curves with negligible hysteresis (<10 mV), high dielectric constant ( ∼ 22), and low leakage currents. The electrical properties of the DyScO3/SiOx/Si stacks were stable up to 800 °C for films on native oxide; however, this limit increased to 900 °C for films on special chemically grown oxide, suggesting further improvement with proper diffusion barrier.
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77.55.-g Dielectric thin films
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
81.40.Gh Other heat and thermomechanical treatments

Improvement in electrical characteristics of high-k Al2O3 gate dielectric by field-assisted nitric oxidation

Kai-Chieh Chuang and Jenn-Gwo Hwu

Appl. Phys. Lett. 89, 232903 (2006); http://dx.doi.org/10.1063/1.2402215 (3 pages) | Cited 3 times

Online Publication Date: 6 December 2006

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The authors perform a simple technique for the improvements in both current density reliability of high-k Al2O3 gate dielectrics. An Al2O3 was prepared by chemical oxidation at an appropriate electrical field in nitric acid at room temperature then furnace annealed at 650 °C in N2. The interface trap-induced capacitance was used to investigate the interfacial property between the gate dielectric Si substrate. On the other hand the stress induced leakage current (SILC) was measured for characterizing the property of bulk oxide. It was found that the electrical characteristics of bulk oxide including leakage breakdown field SILC, were much improved without sacrificing interfacial property. The improvement can be ascribed to the compensation oxidation process.
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84.32.Tt Capacitors
85.30.Tv Field effect devices
81.65.Mq Oxidation

Improved dielectric and ferroelectric properties of high Curie temperature (1−x)BiFeO3–xPbTiO3 ceramics by aliovalent ionic substitution

W.-M. Zhu and Z.-G. Ye

Appl. Phys. Lett. 89, 232904 (2006); http://dx.doi.org/10.1063/1.2397560 (3 pages) | Cited 22 times

Online Publication Date: 7 December 2006

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Ceramics of 0.67Bi(Fe1−xTix)O3+x/2–0.33PbTiO3 (x = 0, 0.005, 0.01, 0.02, 0.04) were prepared by solid state reactions, with a relative density of 94%–97%. The dielectric and ferroelectric properties of the ceramics have been significantly improved by means of aliovalent ionic substitution of Ti4+ for Fe3+, which reduces the electric conductivity. The temperature variation of the dielectric constant has been measured up to the Curie temperature as high as TC = 650 °C. A saturated dielectric hysteresis loop with a remnant polarization (Pr) of 9 μC/cm2 is displayed in the 0.5 mol % Ti4+-substituted sample at room temperature. Pr reaches 17 μC/cm2 in the sample with 2 mol % Ti4+ even though the hysteresis loop is not saturated, suggesting that a much higher saturated polarization can be expected in the Ti4+-substituted BiFeO3–PbTiO3 ceramics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization

Array of dielectric nanocomposite devices using photoepoxy Su-8 as the polymeric phase

Fang Li and Qing-Ming Wang

Appl. Phys. Lett. 89, 232905 (2006); http://dx.doi.org/10.1063/1.2402885 (3 pages) | Cited 3 times

Online Publication Date: 7 December 2006

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An array of dielectric nanocomposite devices in which negative tone photoepoxy Su-8 is used as the polymeric matrix and Ba0.5Sr0.5TO3 nanoparticles as the inclusions is fabricated on silicon substrate. The use of Su-8 necessitates a single step process for both the top electrode deposition and ultraviolet exposure using a shadow mask and direct-current magnetron sputtering in the device fabrication. Scanning electron microscopy examination indicates a uniform distribution of nanoparticles in Su-8 matrix. Effective dielectric constant of the nanocomposites increases with loading concentration with a good agreement with the Maxwell-Garnett and Bruggeman approximations at low concentrations, while dielectric loss is low for all compositions.
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84.32.Tt Capacitors
85.40.Hp Lithography, masks and pattern transfer

Microstructure and enhanced in-plane ferroelectricity of Ba0.7Sr0.3TiO3 thin films grown on MgAl2O4 (001) single-crystal substrate

X. Y. Zhou, T. Heindl, G. K. H. Pang, J. Miao, R. K. Zheng, H. L. W. Chan, C. L. Choy, and Y. Wang

Appl. Phys. Lett. 89, 232906 (2006); http://dx.doi.org/10.1063/1.2402900 (3 pages) | Cited 9 times

Online Publication Date: 7 December 2006

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The microstructure and in-plane dielectric and ferroelectric properties of highly oriented Ba0.7Sr0.3TiO3 (BST) thin film grown on MgAl2O4 (001) single-crystal substrate through pulsed laser deposition were investigated. X-ray diffraction measurements indicated that BST had a distorted lattice with a tetragonality a/c = 1.012. The cross-sectional observation under transmission electron microscope revealed that, while most of BST grains grew epitaxially on MgAl2O4, the film also contained a noticeable amount of misoriented grains and dislocations. The electrical measurements indicated that the film had a shifted Curie temperature (TC = 78 °C) and an enhanced in-plane ferroelectricity (remnant polarization Pr = 7.1 μC/cm2) when compared with BST ceramic (TC ≈ 33 °C and Pr ≈ 0).
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.61.Ng Insulators
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
81.15.Fg Pulsed laser ablation deposition
61.72.-y Defects and impurities in crystals; microstructure

Pseudomorphic molecular beam epitaxy growth of γ-Al2O3(001) on Si(001) and evidence for spontaneous lattice reorientation during epitaxy

C. Merckling, M. El-Kazzi, G. Delhaye, M. Gendry, G. Saint-Girons, G. Hollinger, L. Largeau, and G. Patriarche

Appl. Phys. Lett. 89, 232907 (2006); http://dx.doi.org/10.1063/1.2403902 (3 pages) | Cited 14 times

Online Publication Date: 7 December 2006

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Single crystal γ-Al2O3 thin films have been epitaxially grown by molecular beam epitaxy at 850 °C on Si(001) substrates. Reflection high energy electron diffraction and transmission electron microscopy experiments evidence the good crystalline quality of the Al2O3 layer. The present study shows that the two first monolayers of γ-Al2O3 are (001) oriented and coherently strained on Si. For larger thickness, a transition from (001)- to (111)-oriented Al2O3 occurs, together with the apparition of domains in the layer. In-plane epitaxial relationship between Al2O3 and Si(001) are deduced from these observations.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Lp Transmission electron microscopy (TEM)
68.60.Bs Mechanical and acoustical properties

Structural and electrical properties of neodymium oxide high-k gate dielectrics

Tung-Ming Pan, Jian-Der Lee, Wei-Hao Shu, and Tsung-Te Chen

Appl. Phys. Lett. 89, 232908 (2006); http://dx.doi.org/10.1063/1.2402237 (3 pages) | Cited 16 times

Online Publication Date: 8 December 2006

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In this letter, the authors reported a high-k neodymium oxide gate dielectric grown by reactive rf sputtering. It is found that the Nd2O3 gate dielectric after annealing at 700 °C exhibits excellent electrical properties such as low equivalent oxide thickness, high electric breakdown field, and almost no hysteresis and frequency dispersion in C-V curves. This indicates that annealing at 700 °C treatment can prevent the interfacial layer and silicate formation, reduce a large amount of interface trap, and passivate a large amount of trapped charge at defect sites.
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77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
77.22.Jp Dielectric breakdown and space-charge effects
81.65.Rv Passivation

Coercive fields in ultrathin BaTiO3 capacitors

J. Y. Jo, Y. S. Kim, T. W. Noh, Jong-Gul Yoon, and T. K. Song

Appl. Phys. Lett. 89, 232909 (2006); http://dx.doi.org/10.1063/1.2402238 (3 pages) | Cited 17 times

Online Publication Date: 8 December 2006

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Thickness-dependence of coercive field (EC) was investigated in ultrathin BaTiO3 capacitors with thicknesses (d) between 30 and 5.0 nm. The EC appears nearly independent of d below 15 nm, and decreases slowly as d increases above 15 nm. This behavior can be explained not by effects of interfacial passive layers or strain relaxation, but by domain nuclei formation models. Based on domain nuclei formation models, the observed EC behavior is explainable via a quantitative level. A crossover of domain shape from a half-prolate spheroid to a cylinder is also suggested at d ∼ 15 nm, exhibiting good agreement with experimental results.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors

Realization of a high capacitance density in Bi2Mg2/3Nb4/3O7 pyrochlore thin films deposited directly on polymer substrates for embedded capacitor applications

Jong-Hyun Park, Cheng-Ji Xian, Nak-Jin Seong, Soon-Gil Yoon, Seung-Hyun Son, Hyung-Mi Chung, Jin-Suck Moon, Hyun-Joo Jin, Seung-Eun Lee, Jeong-Won Lee, Hyung-Dong Kang, Yeoul-Kyo Chung, and Yong-Soo Oh

Appl. Phys. Lett. 89, 232910 (2006); http://dx.doi.org/10.1063/1.2402896 (3 pages) | Cited 23 times

Online Publication Date: 8 December 2006

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Bi2Mg2/3Nb4/3O7 (BMN) thin films were deposited on copper clad laminate substrates at temperatures below 150 °C for embedded capacitor applications by pulsed laser deposition. The BMN films deposited at temperatures below 150 °C showed smooth surface morphologies having root mean square roughness of approximately 3.0 nm. 130-nm-thick films deposited at 150 °C exhibit a dielectric constant of 47, a capacitance density of approximately 302 nF/cm2, and breakdown strength of 0.7 MV/cm. The origin exhibiting high dielectric constant in BMN films deposited at low temperatures was attributed to the nanocrystallines having grain sizes of approximately 4.0 nm in the films. The low temperature processed-BMN films are suitable candidate for capacitor applications embodied directly on printed circuit board substrates.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors
77.22.Jp Dielectric breakdown and space-charge effects
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.40.Sz Deposition technology

Ferroelectric properties and poling of BaMgF4 for ultraviolet all solid-state lasers

Kiyoshi Shimamura, Encarnación G. Víllora, Huarong Zeng, Masaru Nakamura, Shunji Takekawa, and Kenji Kitamura

Appl. Phys. Lett. 89, 232911 (2006); http://dx.doi.org/10.1063/1.2403917 (3 pages) | Cited 13 times

Online Publication Date: 8 December 2006

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The ferroelectric properties of bulk BaMgF4 are determined by polarization hysteresis measurements. The spontaneous polarization Ps is found to be 6.6 μC/cm2, while the coercive field Ec varies between 4 and 24 kV/cm, depending exponentially on the frequency. Periodical poling of domains, with a 24 μm period, is demonstrated and evidenced by a selective domain etching.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.80.Dj Domain structure; hysteresis
42.70.Mp Nonlinear optical crystals
77.22.Ej Polarization and depolarization
42.70.Hj Laser materials
42.55.Rz Doped-insulator lasers and other solid state lasers
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