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25 Nov 2002

Volume 81, Issue 22, pp. 4103-4293

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Realizing intrinsic piezoresponse in epitaxial submicron lead zirconate titanate capacitors on Si

V. Nagarajan, A. Stanishevsky, L. Chen, T. Zhao, B.-T. Liu, J. Melngailis, A. L. Roytburd, R. Ramesh, J. Finder, Z. Yu, R. Droopad, and K. Eisenbeiser

Appl. Phys. Lett. 81, 4215 (2002); http://dx.doi.org/10.1063/1.1516857 (3 pages) | Cited 51 times

Online Publication Date: 19 November 2002

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We report on the out-of-plane piezoelectric response (d33), measured via piezoresponse scanning force microscopy, of submicron capacitors fabricated from epitaxial PbZrxTi1−xO3 thin films. Investigations on 1 μm2 and smaller capacitors show that the substrate-induced constraint is dramatically reduced by nanostructuring. At zero field, the experimentally measured values of d33 for clamped as well as submicron capacitors are in good agreement with the predictions from thermodynamic theory. The theory also describes very well the field dependence of the piezoresponse of clamped capacitors of key compositions on the tetragonal side of the PbZrxTi1−xO3 phase diagram as well as the behavior of submicron PbZr0.2Ti0.8O3 (hard ferroelectric) capacitors. However, the field-dependent piezoresponse of submicron capacitors in compositions closer to the morphotropic phase boundary (soft ferroelectrics) is different from the behavior predicted by the theoretical calculations. © 2002 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Tt Capacitors

Suppressed crystallization of Hf-based gate dielectrics by controlled addition of Al2O3 using atomic layer deposition

M.-Y. Ho, H. Gong, G. D. Wilk, B. W. Busch, M. L. Green, W. H. Lin, A. See, S. K. Lahiri, M. E. Loomans, Petri I. Räisänen, and T. Gustafsson

Appl. Phys. Lett. 81, 4218 (2002); http://dx.doi.org/10.1063/1.1522826 (3 pages) | Cited 57 times

Online Publication Date: 19 November 2002

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We demonstrate significantly improved thermal stability of the amorphous phase for hafnium-based gate dielectrics through the controlled addition of Al2O3. The (HfO2)x(Al2O3)1−x films, deposited using atomic layer deposition, exhibit excellent control over a wide range of composition by a suitable choice of the ratio between the Al and Hf precursor pulses. By this method, extremely predictable hafnium aluminate compositions are obtained, with Hf cation fractions ranging from 20% up to 100%, as measured by medium energy ion scattering. Using x-ray diffraction, we show that (HfO2)x(Al2O3)1−x films with Hf:Al ∼ 3:1 (25% Al) remain amorphous up to 900 °C, while films with Hf:Al ∼ 1:3 (75% Al) remain amorphous after a 1050 °C spike anneal. © 2002 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
77.55.-g Dielectric thin films
61.43.Er Other amorphous solids
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.55.Nq Composition and phase identification
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Ultrathin zirconium silicate gate dielectrics with compositional gradation formed by self-organized reactions

Heiji Watanabe

Appl. Phys. Lett. 81, 4221 (2002); http://dx.doi.org/10.1063/1.1525392 (3 pages)

Online Publication Date: 19 November 2002

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Zirconium silicate gate dielectrics with compositional gradation in depth were fabricated by in situ reoxidation of thin metal layers on oxidized Si surfaces. The silicate is composed of a trilayer structure, in which Si-rich layers are formed both at the top and the bottom of the film. The zirconium element is localized at the center of the silicate and, thus, the advantages of the silicate material can be obtained, while keeping sufficient permittivity. The compositionally graded silicates show promising electrical properties, such as a leakage current of less than 0.11 A/cm2 for an equivalent oxide thickness of 1.1 nm and an improved flatband voltage shift that is a result of postdeposition annealing and oxidation. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.65.Mq Oxidation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.22.Ch Permittivity (dielectric function)
61.72.Cc Kinetics of defect formation and annealing
68.55.Nq Composition and phase identification

Grain-boundary and crack effects on the dielectric response of high-permittivity films and ceramics

I. Rychetský, J. Petzelt, and T. Ostapchuk

Appl. Phys. Lett. 81, 4224 (2002); http://dx.doi.org/10.1063/1.1525394 (3 pages) | Cited 28 times

Online Publication Date: 19 November 2002

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Grain-boundary and crack effects on the dielectric response of high-permittivity films and ceramics were analyzed using the generalized effective-medium approximation. It was demonstrated that the brick-wall and coated spheres models, which become equivalent for a small porosity, best describe the strong reduction of the dielectric response and hardening of the soft-mode frequency recently revealed in SrTiO3 films and PbZrO3 ceramics. © 2002 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
61.72.Mm Grain and twin boundaries
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
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)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Characterization of silicate/Si(001) interfaces

M. Copel, E. Cartier, V. Narayanan, M. C. Reuter, S. Guha, and N. Bojarczuk

Appl. Phys. Lett. 81, 4227 (2002); http://dx.doi.org/10.1063/1.1524296 (3 pages) | Cited 27 times

Online Publication Date: 19 November 2002

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Many of the proposed high permittivity gate dielectrics for silicon-based microelectronics rely on a stack configuration, with an SiO2 buffer layer to provide an interface. We describe a means for creating gate dielectrics with a direct yttrium silicate–silicon interface through the solid-state reaction of yttria and silicon oxynitride, avoiding the preparation of an oxide-free silicon surface. Characterization by medium-energy ion scattering indicates complete consumption of the underlying oxide through silicate formation during high-temperature annealing. Furthermore, the silicate dielectric exhibits small flat-band voltage shifts, indicating low quantities of charge, without passivation steps. Creation of a silicate–silicon interfaces by a simple route may enable the study of an alternate class of dielectrics. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Ct Interface structure and roughness
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Degradation of ferroelectric properties in integrated Pt/SrBi2Ta2O9/Pt capacitor by impurity diffusion from interlevel dielectric layer

Sang-Hyun Oh, Suk-Kyoung Hong, Jin Gu Kim, Jin Yong Seong, Young-Jin Park, and Deok-Won Lee

Appl. Phys. Lett. 81, 4230 (2002); http://dx.doi.org/10.1063/1.1525060 (3 pages) | Cited 4 times

Online Publication Date: 19 November 2002

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The ferroelectric properties of integrated Pt/SrBi2Ta2O9 (SBT)/Pt capacitors with boron (B)- and phosphorus (P)-doped silicate glass (BPSG) as an interlevel dielectric layer were investigated. After annealing at 800 °C to densify the BPSG, a significant reduction in remanent polarization was observed. Both transmission electron microscopy and nanoprobe energy dispersive spectroscopy analysis showed bismuth (Bi) and P interdiffusion across the interface between the SBT and BPSG layers. This strongly suggests that Pt/SBT/Pt capacitor degradation results from Bi loss in the surface region of the SBT layer, which is induced by P diffusion into the SBT. The degradation in ferroelectric properties was prevented by inserting a thin undoped silicate glass (USG) layer between the SBT and the BPSG, which blocked P diffusion. From the USG thickness dependence of the remanent polarization, P-induced degradation was also verified. © 2002 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
84.32.Tt Capacitors
68.35.Fx Diffusion; interface formation
85.50.Gk Non-volatile ferroelectric memories
77.55.-g Dielectric thin films

Modeling of Si 2p core-level shifts at Si–(ZrO2)x(SiO2)1−x interfaces

Feliciano Giustino, Angelo Bongiorno, and Alfredo Pasquarello

Appl. Phys. Lett. 81, 4233 (2002); http://dx.doi.org/10.1063/1.1526172 (3 pages) | Cited 10 times

Online Publication Date: 19 November 2002

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We model Si 2p core-level shifts at Si–(ZrO2)x(SiO2)1−x interfaces for varying Zr content x. Using a first-principles approach, we calculate Si 2p shifts for a model interface and for cluster models, and establish the validity of a linear dependence of these shifts on both the number of second-neighbor Zr atoms and the O coordination of these Zr atoms. Applying this relation to model structures of amorphous Zr silicates generated by classical molecular dynamics, we find that the Si 2p line shifts to lower binding energies with increasing Zr content x, in accord with experimental data. © 2002 American Institute of Physics.
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73.20.-r Electron states at surfaces and interfaces
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
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