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4 Oct 2004

Volume 85, Issue 14, pp. 2679-2983

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Appl. Phys. Lett. 85, 2860 (2004); http://dx.doi.org/10.1063/1.1799245 (3 pages)

Priya Mahadevan and Alex Zunger
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Large enhancement of the piezoelectric response in perovskite crystals by electric bias field antiparallel to polarization

Marko Budimir, Dragan Damjanovic, and Nava Setter

Appl. Phys. Lett. 85, 2890 (2004); http://dx.doi.org/10.1063/1.1799231 (3 pages) | Cited 18 times

Online Publication Date: 14 October 2004

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Using Landau–Ginzburg–Devonshire theory and tetragonal BaTiO3 as an example, this letter demonstrates that strong electric bias fields applied antiparallel to spontaneous polarization may lead to a large enhancement of piezoelectric properties in monodomain perovskite crystals with multiple phase transitions. At temperatures close to tetragonal–orthorhombic phase transition, the largest enhancement is approximately along the [111] axis. The enhancement is due to the field induced dielectric softening of the crystal.
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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
77.80.B- Phase transitions and Curie point

Electrical characteristics and suppressed boron penetration behavior of thermally stable HfTaO gate dielectrics with polycrystalline-silicon gate

Xiongfei Yu, Chunxiang Zhu, M. F. Li, Albert Chin, A. Y. Du, W. D. Wang, and Dim-Lee Kwong

Appl. Phys. Lett. 85, 2893 (2004); http://dx.doi.org/10.1063/1.1795369 (3 pages) | Cited 22 times

Online Publication Date: 14 October 2004

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The thermal stability and electrical characteristics of HfTaO gate dielectric with polycrystalline-silicon gate have been investigated. The incorporation of Ta into HfO2 enhances the crystallization temperature of film dramatically. Transmission electron microscopy micrographs confirm that HfTaO with 43% Ta film remains amorphous even after activation annealing at 950 °C for 30 s, and the formation of low-κ interfacial layer is observably reduced. The capacitance–voltage curve of metal–oxide–semiconductor capacitor using HfTaO gate dielectric fits well with simulated curve, indicating good interface property between HfTaO and substrate. In addition, the boron penetration behaviors of HfTaO films are sufficiently suppressed as manifested by the narrow flat-band voltage shift. The negligible flat-band voltage shift in HfTaO with 43% Ta film is observed and attributed to its amorphous structure after device fabrication.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
68.37.Lp Transmission electron microscopy (TEM)

Piezoresponse in the light of surface adsorbates: Relevance of defined surface conditions for perovskite materials

F. Peter, K. Szot, R. Waser, B. Reichenberg, S. Tiedke, and J. Szade

Appl. Phys. Lett. 85, 2896 (2004); http://dx.doi.org/10.1063/1.1799241 (3 pages) | Cited 29 times

Online Publication Date: 14 October 2004

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We report on the influence of a surface layer prevailing on perovskites on the piezoelectricity measured by piezoresponse force microscopy. Surface sensitive measurements show that this layer consists of chemisorbates and physisorbates. The surface layer can be removed to a large extent by heating the sample under ultrahigh vacuum conditions. It is shown that the effect of this treatment on the piezoresponse of the material is significant as the potential difference applied to the sample is no longer reduced by a voltage drop across the adsorbate layer. As a consequence the internal electric field is higher in comparison to the presence of a layer and so the piezoresponse is higher as well.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
68.43.Mn Adsorption kinetics
68.43.Fg Adsorbate structure (binding sites, geometry)
77.65.Bn Piezoelectric and electrostrictive constants
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
68.60.Wm Other nonelectronic physical properties

Maxwell–Wagner effect in hexagonal BaTiO3 single crystals grown by containerless processing

Jianding Yu, Paul-François Paradis, Takehiko Ishikawa, and Shinichi Yoda

Appl. Phys. Lett. 85, 2899 (2004); http://dx.doi.org/10.1063/1.1799246 (3 pages) | Cited 22 times

Online Publication Date: 14 October 2004

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Oxygen-deficient hexagonal BaTiO3 single crystals, with dielectric constant ε′∼105 and loss component tan δ∼0.13 at room temperature and a linear temperature dependence of ε′ in the range 70–100 K, was analyzed by impedance spectroscopy analysis. Two capacitors, bulk and interfacial boundary layer, were observed, and the colossal dielectric constant was mainly dominated by the interfacial boundary layers due to Maxwell–Wagner effect. After annealing the oxygen-deficient hexagonal BaTiO3 at 663 K, the ε′ and tan δ became, respectively, 2×104 and 0.07 at room temperature. This work showed an important technological implication as annealing at lower temperatures would help to obtain materials with tailored dielectric properties.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
81.40.Gh Other heat and thermomechanical treatments

Interfacial characteristics of HfO2 grown on nitrided Ge (100) substrates by atomic-layer deposition

Hyoungsub Kim, Paul C. McIntyre, Chi On Chui, Krishna C. Saraswat, and Mann-Ho Cho

Appl. Phys. Lett. 85, 2902 (2004); http://dx.doi.org/10.1063/1.1797564 (3 pages) | Cited 67 times

Online Publication Date: 14 October 2004

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The microstructural and electrical properties of Ge-based metal–oxide–semiconductor capacitors containing high-k gate dielectric layers were investigated with and without the presence of a GeOxNy interface layer. The effect of this nitrided layer on thermal stability of the metal oxide/Ge structures was probed by medium energy ion energy spectroscopy (MEIS). Atomic-layer deposited HfO2 on a chemical oxide-terminated Ge (100) surface exhibited poor capacitance–voltage behavior; however, direct substrate surface nitridation at 600 °C in NH3 ambient before HfO2 deposition improved the carrier trapping characteristics. Diffusion of metal impurities (including Hf) into the interfacial oxide/Ge-substrate may be an important source of the measured degradation of electrical properties. MEIS results suggested that the GeOxNy interface layer may inhibit Hf diffusion into the underlying semiconductor at the temperatures investigated.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
81.65.Rv Passivation
66.30.J- Diffusion of impurities
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Suppression of antiphase domain boundary formation in Ba0.5Sr0.5TiO3 films grown on vicinal MgO substrates

H. Zheng, L. Salamanca-Riba, R. Ramesh, and H. Li

Appl. Phys. Lett. 85, 2905 (2004); http://dx.doi.org/10.1063/1.1804609 (3 pages) | Cited 6 times

Online Publication Date: 14 October 2004

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Ba0.5Sr0.5TiO3 (BST) thin films were epitaxially grown on MgO vicinal substrates by pulsed-laser deposition and molecular-beam epitaxy. [001] oriented MgO substrates with 2° and 5° miscut toward [010] were selected. The nucleation of antiphase domain boundaries in the direction parallel to the step edges is greatly reduced in BST films grown on the vicinal substrates compared to the films grown on flat substrates. The reduction in antiphase domain boundaries gives rise to a higher dielectric constant when the electrodes are parallel to the direction of the steps, by about 280–460, than in the perpendicular direction.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
77.22.Ch Permittivity (dielectric function)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Fg Pulsed laser ablation deposition
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