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29 Sep 2003

Volume 83, Issue 13, pp. 2503-2719

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 2680 (2003); http://dx.doi.org/10.1063/1.1614845 (3 pages)

F. Nakajima, Y. Miyoshi, J. Motohisa, and T. Fukui
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Carrier loss and luminescence degradation in green-light-emitting InGaN quantum wells with micron-scale indium clusters

Yong-Hoon Cho, S. K. Lee, H. S. Kwack, J. Y. Kim, K. S. Lim, H. M. Kim, T. W. Kang, S. N. Lee, M. S. Seon, O. H. Nam, and Y. J. Park

Appl. Phys. Lett. 83, 2578 (2003); http://dx.doi.org/10.1063/1.1613043 (3 pages) | Cited 26 times

Online Publication Date: 23 September 2003

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Influence of the size of indium clusters on optical properties of green-light-emitting InGaN quantum wells (QWs) was investigated by photoluminescence (PL), cathodoluminescence, PL excitation, and time-resolved PL techniques. Low luminescence efficiency was observed for green-light-emitting InGaN QWs with micron-sized indium clusters, in contrast to the case of InGaN QWs with submicron-sized small indium segregation. Both the thermal activation energy and the carrier lifetime dramatically decreased, while a large Stokes-like shift between absorption edge and PL peak energy was still observed for the InGaN QWs with micron-sized indium clusters. These facts indicate that the effective potential barrier between radiative and nonradiative channels (thus effective carrier localization) rapidly decreases due to the formation of micron-sized large indium clusters possessing a number of nonradiative centers, leading to significant luminescence degradation. © 2003 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence
78.47.-p Spectroscopy of solid state dynamics

Role of yttrium in glass formation of Fe-based bulk metallic glasses

Z. P. Lu, C. T. Liu, and W. D. Porter

Appl. Phys. Lett. 83, 2581 (2003); http://dx.doi.org/10.1063/1.1614833 (3 pages) | Cited 91 times

Online Publication Date: 23 September 2003

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In this study, we discovered that a small addition of Y is very effective in improving glass-forming ability of Fe-based alloys. As-cast bulk amorphous alloys containing 2 at. % Y showed large thermal stability, with glass transition temperatures above 900 K and supercooled liquid regions above 55 K, and high strength, with Vickers hardnesses larger than HV 1200. The beneficial effect of Y on glass formation is twofold: (1) Y adjusted the compositions closer to the eutectic and thus lowered their liquidus temperatures, and (2) Y improved the manufacturability of these alloys by scavenging the oxygen impurity from it via the formation of innocuous yttrium oxides. © 2003 American Institute of Physics.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
62.20.Qp Friction, tribology, and hardness

Properties of Bulk AlN grown by thermodecomposition of AlCl3⋅NH3

J. A. Freitas, G. C. B. Braga, E. Silveira, J. G. Tischler, and M. Fatemi

Appl. Phys. Lett. 83, 2584 (2003); http://dx.doi.org/10.1063/1.1614418 (3 pages) | Cited 14 times

Online Publication Date: 23 September 2003

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Self-nucleated bulk AlN crystals were grown by thermodecomposition of AlCl3⋅NH3 vaporized in the low-temperature zone of a two-zone furnace. X-ray diffraction of the AlN crystals show single lines with a small linewidth indicating high single-crystalline quality. Polarized Raman scattering experiments of these samples confirm the x-ray results based on the detection of a small linewidth for all allowed optical phonons. Low-temperature cathodoluminescence spectra show very sharp emission bands close to the optical band gap, which have been assigned to free-excitons A and B, and exciton-bound to shallow neutral impurity. The latter has a full width at half maximum smaller than 1.0 meV. © 2003 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.10.Bk Growth from vapor
78.60.Hk Cathodoluminescence, ionoluminescence
78.30.Fs III-V and II-VI semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
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A comparative study of GaSb (100) surface passivation by aqueous and nonaqueous solutions

Z. Y. Liu, T. F. Kuech, and D. A. Saulys

Appl. Phys. Lett. 83, 2587 (2003); http://dx.doi.org/10.1063/1.1613994 (3 pages) | Cited 15 times

Online Publication Date: 23 September 2003

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We report a nonaqueous passivation regime consisting of Na2S/benzene/15-crown-5/oxidant. The use of a nonpolar, aprotic organic medium required the addition of a specific chelating agent (15-crown-5) to solubilize sodium sulfide, and organic oxidizing agents (anthraquinone, benzophenone, etc.) to act as electron acceptors. The surface optical and chemical properties of GaSb surfaces after aqueous and nonaqueous sulfide treatments were compared. Nonaqueous passivation resulted in higher photoluminescence (PL) intensity, lower oxide content, and a less amount of elemental Sb than aqueous passivation. The PL intensity from passivated surfaces was correlated with the standard reduction potentials of electron acceptors. © 2003 American Institute of Physics.
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81.65.Rv Passivation
68.35.Dv Composition, segregation; defects and impurities
78.55.Cr III-V semiconductors
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors

Magnetic-field-induced localization of electrons in InGaN/GaN multiple quantum wells

B. Arnaudov, T. Paskova, O. Valassiades, P. P. Paskov, S. Evtimova, B. Monemar, and M. Heuken

Appl. Phys. Lett. 83, 2590 (2003); http://dx.doi.org/10.1063/1.1613999 (3 pages) | Cited 1 time

Online Publication Date: 23 September 2003

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We study longitudinal electron transport in InGaN/GaN multiple quantum wells (MQWs) at moderate magnetic fields. We observe a stepwise behavior of both the Hall coefficient and magnetoresistivity. The peculiarities are explained by a magnetic-field-induced localization of electrons in a two-dimensional (2D) potential relief of the InGaN MQW due to composition fluctuations. We extend the model for a magnetic localization of electrons, treating every QW like a quasi-2D system with a cylindrical potential relief. The calculated values of the decrease of the sheet electron concentrations in a magnetic field based on such an assumption for 2D density of states in a InGaN MQW system are in good accordance with the experimentally obtained values. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
73.63.Hs Quantum wells
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.At Surface states, band structure, electron density of states

Low Schottky barriers on n-type silicon (001)

Meng Tao, Shruddha Agarwal, Darshak Udeshi, Nasir Basit, Eduardo Maldonado, and Wiley P. Kirk

Appl. Phys. Lett. 83, 2593 (2003); http://dx.doi.org/10.1063/1.1613357 (3 pages) | Cited 30 times

Online Publication Date: 23 September 2003

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It has been reported that no metal shows a Schottky barrier of less than 0.4 eV on n-type silicon (001). This is attributed to interface states between metal and silicon (001), which pin the interface Fermi level and make the Schottky barrier more or less independent of the metal work function. We demonstrate that, by terminating dangling bonds and relaxing strained bonds on the silicon (001) surface with a monolayer of selenium, low Schottky barriers can be obtained on n-type silicon (001). Aluminum and chromium show barrier heights of 0.08 and 0.26 eV on n-type silicon (001), respectively. These results agree well with the ideal Schottky barrier heights for aluminum and chromium on n-type silicon (001), but are significantly different from the experimental barrier heights known for four decades for these metals on n-type silicon (001). © 2003 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
73.20.At Surface states, band structure, electron density of states

Impedance up to 6 GHz in La0.67Sr0.33MnO3 thin films

L. Reversat, P. Crozat, R. Lyonnet, C. Dupas, and J.-P. Contour

Appl. Phys. Lett. 83, 2596 (2003); http://dx.doi.org/10.1063/1.1606868 (3 pages) | Cited 4 times

Online Publication Date: 23 September 2003

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The ac electrical impedance of a 400-nm-thick La0.67Sr0.33MnO3 thin film (on MgO) has been measured in the frequency range from 30 MHz up to 6 GHz using etched strips. The impedance is found to be nearly a constant resistance that is equal to the dc resistance. The only deviations, in the order of their magnitude, are: (i) the contact pad impedance at low frequency, (ii) a small inductive part in the impedance of the material, and (iii) a low decrease of the resistance above 3 GHz. © 2003 American Institute of Physics.
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73.50.Mx High-frequency effects; plasma effects
72.30.+q High-frequency effects; plasma effects
72.20.Fr Low-field transport and mobility; piezoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films

GaN/AlGaN multiple quantum wells on a-plane GaN pillars for stripe-geometry nonpolar ultraviolet light-emitting devices

W. H. Sun, J. W. Yang, C. Q. Chen, J. P. Zhang, M. E. Gaevski, E. Kuokstis, V. Adivarahan, H. M. Wang, Z. Gong, M. Su, and M. Asif Khan

Appl. Phys. Lett. 83, 2599 (2003); http://dx.doi.org/10.1063/1.1614835 (3 pages) | Cited 27 times

Online Publication Date: 23 September 2003

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We investigated the growth of GaN/Al0.20Ga0.80N multiple quantum wells (MQWs) on selective-area-grown a-plane GaN pillars over r-plane sapphire. In contrast to the MQWs grown on planar a-plane GaN templates, these GaN/Al0.20Ga0.8N MQWs on the pillars exhibited pit-free and atomically smooth surface morphology. Their structural quality and their UV emission (at 357 nm) increased with the underlying pillar height. The epitaxy of GaN/AlGaN MQWs on the selective-area-grown pillars is thus a promising and simple approach for fabricating stripe-geometry, high-efficiency, nonpolar UV emitters. © 2003 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
68.65.Fg Quantum wells

Kelvin probe spectroscopy of a two-dimensional electron gas below 300 mK

T. Vančura, S. Kičin, T. Ihn, K. Ensslin, M. Bichler, and W. Wegscheider

Appl. Phys. Lett. 83, 2602 (2003); http://dx.doi.org/10.1063/1.1614836 (3 pages) | Cited 10 times

Online Publication Date: 23 September 2003

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A scanning force microscope with a base temperature below 300 mK is used for measuring the local electron density of a two-dimensional electron gas embedded in a Ga[Al]As heterostructure. At different separations between atomic force microscope tip and sample, a dc voltage is applied between the tip and the electron gas while simultaneously recording the frequency shift of the oscillating tip. Using a plate capacitor model, the local electron density can be extracted from the data. The result coincides within 10% with the data obtained from transport measurements. © 2003 American Institute of Physics.
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73.63.-b Electronic transport in nanoscale materials and structures

Inelastic electron tunneling spectroscopy study of ultrathin HfO2 and HfAlO

Wei He and T. P. Ma

Appl. Phys. Lett. 83, 2605 (2003); http://dx.doi.org/10.1063/1.1614837 (3 pages) | Cited 12 times

Online Publication Date: 23 September 2003

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We have studied inelastic electron tunneling spectroscopy (IETS) in silicon metal-oxide-semiconductor systems with HfO2 and aluminum-doped HfO2 (HfAlO) as gate dielectrics. Samples with a thermal SiO2 layer ( ∼ 2 nm) were used to obtain reference spectra for the study. Information on chemical bonding structures and compositions of ultrathin HfO2 and HfAlO has been revealed by the IETS data. The bias polarity dependence of IETS has enabled differentiation of microstructures either near the gate electrode interface or near the silicon substrate interface. © 2003 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
73.40.Ty Semiconductor-insulator-semiconductor structures
77.55.-g Dielectric thin films

Deep traps in unpassivated and Sc2O3-passivated AlGaN/GaN high electron mobility transistors

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, V. N. Danilin, T. A. Zhukova, B. Luo, F. Ren, B. P. Gila, A. H. Onstine, C. R. Abernathy, and S. J. Pearton

Appl. Phys. Lett. 83, 2608 (2003); http://dx.doi.org/10.1063/1.1614839 (3 pages) | Cited 10 times

Online Publication Date: 23 September 2003

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Sc2O3 thin-film layers deposited by rf plasma-assisted molecular-beam epitaxy were found to significantly reduce the concentration of prominent surface traps with activation energies of 1 and 0.9 eV on AlGaN/GaN high electron mobility transistors (HEMTs). The surface passivation is accompanied by effective mitigation of the current collapse observed under rf conditions in HEMTs without Sc2O3. The passivation is stable to post-deposition annealing temperatures of 400 °C and device degradation at higher temperatures is due to reaction of the gate metal with the AlGaN. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
81.65.Rv Passivation
61.72.Cc Kinetics of defect formation and annealing

Characteristics of erbium-silicided n-type Schottky barrier tunnel transistors

Moongyu Jang, Jihun Oh, Sunglyul Maeng, Wonju Cho, Seongjae Lee, Kicheon Kang, and Kyoungwan Park

Appl. Phys. Lett. 83, 2611 (2003); http://dx.doi.org/10.1063/1.1614441 (3 pages) | Cited 17 times

Online Publication Date: 23 September 2003

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The current–voltage characteristics of erbium-silicided n-type Schottky barrier tunnel transistors (SBTTs) are discussed. The n-type SBTTs with 60 nm gate lengths shows typical transistor behaviors in drain current to drain voltage characteristics. The drain current on/off ratio is about 105 at low drain voltage regime in drain current to gate voltage characteristics. However, the on/off ratio tends to decrease as the drain voltage increases. From the numerical simulation results, the increase of off-current is mainly attributed to the thermionic current and the increase of drain current is mainly attributed to the tunneling current, respectively. This phenomenon is explained by using drain induced Schottky barrier thickness thinning effect. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.De Semiconductor-device characterization, design, and modeling

Magneto-optical properties of GaAsSb/GaAs quantum wells

R. T. Senger, K. K. Bajaj, E. D. Jones, N. A. Modine, K. E. Waldrip, F. Jalali, J. F. Klem, G. M. Peake, X. Wei, and S. W. Tozer

Appl. Phys. Lett. 83, 2614 (2003); http://dx.doi.org/10.1063/1.1615680 (3 pages) | Cited 7 times

Online Publication Date: 23 September 2003

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We have measured the diamagnetic shift of a heavy-hole exciton in a single 60 Å wide GaAs0.7Sb0.3/GaAs quantum well as a function of magnetic field up to 32 T at 1.3 K using photoluminescence spectroscopy. The sample was grown on (001)-oriented GaAs substrate using solid-source molecular beam epitaxy. We have calculated the variation of the diamagnetic shift as a function of magnetic field using a variational approach and a free exciton model. We assumed a weak type-I conduction-band lineup in our calculations. We found that the values thus obtained are more than twice as large as the observed values. A similar calculation assuming a complete localization of the heavy hole leads to the values of the diamagnetic shift which agree very well with the experimental data. Our study suggests that the excitons are strongly localized in GaAs0.7Sb0.3/GaAs quantum well structures at low temperatures, and that this heterostructure has a weak type-I conduction-band lineup. © 2003 American Institute of Physics.
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78.67.De Quantum wells
78.20.Ls Magneto-optical effects
78.55.Cr III-V semiconductors
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
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Magnetic domain wall motion triggered by an electric current

M. Tsoi, R. E. Fontana, and S. S. P. Parkin

Appl. Phys. Lett. 83, 2617 (2003); http://dx.doi.org/10.1063/1.1578165 (3 pages) | Cited 93 times

Online Publication Date: 23 September 2003

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The current-induced propagation of magnetic domain walls is studied in CoFe nanoconstrictions patterned by electron beam lithography. Propagation of the walls was confirmed by magnetic force microscopy imaging. The device geometry allows us to distinguish between various mechanisms of interaction between electric current and domain walls: a mechanism in which spin transfer associated with current traversing a domain wall dominates. As expected for such a mechanism the domain wall propagation occurs in the direction of electron current flow and has a current threshold of the order ∼ 1011 A/m2. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys

Temperature dependence of the switching field and its distribution function in Fe-based bistable microwires

R. Varga, K. L. Garcia, A. Zhukov, M. Vazquez, and P. Vojtanik

Appl. Phys. Lett. 83, 2620 (2003); http://dx.doi.org/10.1063/1.1613048 (3 pages) | Cited 22 times

Online Publication Date: 23 September 2003

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The switching field distribution for magnetization reversal in a single Barkhausen jump of a bistable Fe-based amorphous microwire as well as its temperature dependence have been investigated in the temperature range from 77 to 450 K. Two processes have been identified to be responsible for the temperature dependence of the switching field: magnetostrictive volume domain wall pinning on stresses and relaxation effects due to local structural rearrangements. While at low temperatures, pinning on the atomic level defects plays the dominant role, magnetostrictive pinning becomes more important at intermediate temperatures. A simple model is proposed considering both energy contributions that fits reasonably well with experimental data and allows us to interpret additionally the observed temperature dependence of the switching field fluctuations. © 2003 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Jk Magnetization reversal mechanisms
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.80.+q Magnetomechanical effects, magnetostriction

Enhanced magnetoresistance in the complex perovskite LaCu3Mn4O12

J. A. Alonso, J. Sánchez-Benítez, A. De Andrés, M. J. Martínez-Lope, M. T. Casais, and J. L. Martínez

Appl. Phys. Lett. 83, 2623 (2003); http://dx.doi.org/10.1063/1.1611647 (3 pages) | Cited 35 times

Online Publication Date: 23 September 2003

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Moderate-pressure techniques (P = 2 GPa) have been used to prepare the complex LaCu3Mn4O12 perovskite. It has been characterized by neutron powder diffraction, magnetic, and magnetotransport measurements. This material is ferrimagnetic below TC = 361 K. The magnetoresistance (MR) is enhanced with respect to that of CaCu3Mn4O12 due to the effective electronic injection that dramatically reduces the bulk resistivity, thus promoting the grain-boundary contribution to the electrical resistance. Values of low-field MR close to 3% at room temperature are achieved for magnetic fields of 1 T. © 2003 American Institute of Physics.
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75.47.Lx Magnetic oxides
75.47.Gk Colossal magnetoresistance
75.50.Gg Ferrimagnetics

Rigid vortices in MgB2

Hao Jin, Hai-Hu Wen, Hai-Peng Yang, Zhi-Yong Liu, Zhi-An Ren, Guang-Can Che, and Zhong-Xian Zhao

Appl. Phys. Lett. 83, 2626 (2003); http://dx.doi.org/10.1063/1.1613035 (3 pages) | Cited 12 times

Online Publication Date: 23 September 2003

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Magnetic relaxation of high-pressure synthesized MgB2 bulks with different thickness is investigated. It is found that the superconducting diamagnetic moment depends on time in a logarithmic way: the flux-creep activation energy decreases linearly with the current density (as expected by Kim–Anderson model) and the activation energy increases linearly with the thickness of sample when it is thinner than about 1 mm. These features suggest that the vortices in the MgB2 are rather rigid, and the pinning and creep can be well described by Kim–Anderson model. © 2003 American Institute of Physics.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Op Mixed states, critical fields, and surface sheaths
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Tunnel magnetoresistance in nanojunctions based on Sr2FeMoO6

M. Bibes, K. Bouzehouane, A. Barthélémy, M. Besse, S. Fusil, M. Bowen, P. Seneor, J. Carrey, V. Cros, A. Vaurès, J.-P. Contour, and A. Fert

Appl. Phys. Lett. 83, 2629 (2003); http://dx.doi.org/10.1063/1.1612902 (3 pages) | Cited 47 times

Online Publication Date: 23 September 2003

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We report on the observation of magnetoresistance in a Sr2FeMoO6 (SFMO)-based tunnel junction. This result is obtained by combining a three-step process for the growth of the Sr2FeMoO6 layer by pulsed laser deposition with a technology allowing the definition of nanometer-sized junctions. A clear positive magnetoresistive signal of 50% is obtained at low temperature in a Sr2FeMoO6/SrTiO3/Co junction. Since the SrTiO3/Co interface is known to have a negative spin polarization of about 20%, this result yields a negative spin polarization of SFMO, which we find to amount to more than 85% in our film. This confirms the half-metallic character of this compound, predicted by band structure calculations. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.50.Dd Nonmetallic ferromagnetic materials

Effect of microstructural evolution on magnetic property of Mn-implanted p-type GaN

Jeong Min Baik, Hyung Seok Kim, Chan Gyung Park, and Jong-Lam Lee

Appl. Phys. Lett. 83, 2632 (2003); http://dx.doi.org/10.1063/1.1615676 (3 pages) | Cited 9 times

Online Publication Date: 23 September 2003

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The microstructural evolution of Mn-implanted p-type GaN has been studied using cross-sectional transmission electron microscopy. As Mn3Ga nanoclusters (3–7 nm) with a hexagonal structure were produced by annealing ( ⩽ 800 °C), the weak ferromagnetic property emerged. Higher-temperature annealing ( ≥ 900 °C) reduced the ferromagnetic signal and produced antiferromagnetic Mn-nitride nanoclusters, such as Mn6N2.58 and Mn3N2. This provides evidence that the ferromagnetic property was deeply related to microstructural changes of nanoclusters. © 2003 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
75.50.Pp Magnetic semiconductors
61.46.-w Structure of nanoscale materials
75.50.Tt Fine-particle systems; nanocrystalline materials
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Dielectric response of relaxor ferroelectrics in the time-domain

Hyun M. Jang

Appl. Phys. Lett. 83, 2635 (2003); http://dx.doi.org/10.1063/1.1613050 (3 pages) | Cited 1 time

Online Publication Date: 23 September 2003

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Dielectric response of relaxor ferroelectrics was analyzed in the time-domain by evaluating the relaxation-time (τ) distribution of Pb(Mg1/3Nb2/3)O3-10 mol % PbTiO3 using the method of Tikhonov regularization. The distribution function g(τ) became exponentially broad and flat as temperature approached a certain critical point ( ∼ 230 K), indicating the advent of the frozen polar domains with infinitely long τ in a matrix of the thermally activated dynamic polar domains. The dielectric response of the high-temperature relaxation part was then separately estimated with the help of the two-states-polarization model. The estimated g(τ) of the relaxation part showed logarithmic Gaussian behavior, which manifested an ergodicity in the thermally activated flips of dynamic polarizations at high temperatures. In contrast to this, a resonance kernel was postulated to describe the dielectric response of the frozen polar domains at lower temperatures. © 2003 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Interfacial growth in HfOxNy gate dielectrics deposited using [(C2H5)2N]4Hf with O2 and NO

M. Lee, Z.-H. Lu, W.-T. Ng, D. Landheer, X. Wu, and S. Moisa

Appl. Phys. Lett. 83, 2638 (2003); http://dx.doi.org/10.1063/1.1608488 (3 pages) | Cited 39 times

Online Publication Date: 23 September 2003

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The interface growth by oxygen diffusion has been investigated for 5 nm thick HfOxNy gate-quality dielectric films deposited on Si(100) by low-pressure pulsed metalorganic chemical vapor deposition. Analysis by x-ray photoelectron spectroscopy of the films deposited using the precursor tetrakis (diethylamido) hafnium with O2 showed that the films contained 4 at. % nitrogen. This increased to 11 at. % N when NO was used as the oxidant. Significant growth of the interface layer was observed for films exposed to air at ambient temperature and lower rates of growth were observed for vacuum annealed films and those with the higher N content. For films annealed in O2 at temperatures in the range 600–900 °C, the activation energies of the interfacial growth were 0.36 and 0.25 eV for N concentrations of 11 and 4 at. %, respectively. The results were interpreted in terms of atomic oxygen formation in the bulk and reaction at the interface. The increase in N incorporation from 4 to 11 at. % increases the crystallization temperature from between 500 and 600 °C to between 600 and 700 °C. © 2003 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.A- Nucleation and growth
61.72.Cc Kinetics of defect formation and annealing

Rayleigh type behavior of the Young's modulus of unpoled ferroelectric ceramics and its dependence on temperature

M. Algueró, B. Jiménez, and L. Pardo

Appl. Phys. Lett. 83, 2641 (2003); http://dx.doi.org/10.1063/1.1614414 (3 pages) | Cited 9 times

Online Publication Date: 23 September 2003

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The dependence on stress of the low frequency Young's modulus and mechanical losses of unpoled ferroelectric ceramics has been studied as a function of temperature. The Young's modulus of unpoled Pb(Zr,Ti)O3 (PZT) showed a Rayleigh type dependence, analogous to the one already described for the longitudinal piezoelectric coefficient. This has been associated to ferroelectric/ferroelastic domain wall movements across, and their pinning/depinning on, randomly distributed defects. The Rayleigh coefficient was found to increase with temperature. The activation energy of the Rayleigh process was obtained, which must be related to the pinning energy. The Young's modulus of Mn doped 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 showed no stress dependence. © 2003 American Institute of Physics.
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62.20.D- Elasticity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis

Calculation of effective dielectric constants for advanced interconnect structures with low-k dielectrics

Seung-Hyun Rhee, Martin D. Radwin, Man Fai Ng, Jeremy I. Martin, and Darrell Erb

Appl. Phys. Lett. 83, 2644 (2003); http://dx.doi.org/10.1063/1.1614438 (3 pages) | Cited 6 times

Online Publication Date: 23 September 2003

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Effective dielectric constants of advanced interconnects with low-k and ultra-low-k dielectrics were evaluated by two-dimensional capacitance analysis. The analysis was performed for interconnect design rules proposed for 65 nm node high-performance integration. Interconnects with various pitches and integration schemes were examined, and the effects of supporting dielectric layers including cap layer, chemical mechanical polishing stop layer, and etch stop layer were evaluated. The results indicated that the use of the supporting layers greatly affects the effective dielectric constant of interconnect structures. The impacts of the supporting dielectric layers on the effective dielectric constant were evaluated quantitatively, and the implications on back-end-of-line integration schemes were discussed. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
77.22.Ch Permittivity (dielectric function)

Local epitaxial growth of ZrO2 on Ge (100) substrates by atomic layer epitaxy

Hyoungsub Kim, Chi On Chui, Krishna C. Saraswat, and Paul C. McIntyre

Appl. Phys. Lett. 83, 2647 (2003); http://dx.doi.org/10.1063/1.1613031 (3 pages) | Cited 65 times

Online Publication Date: 23 September 2003

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High-k dielectric deposition processes for gate dielectric preparation on Si surfaces usually result in the unavoidable and uncontrolled formation of a thin interfacial oxide layer. Atomic layer deposition of ∼55-Å ZrO2 film on a Ge (100) substrate using ZrCl4 and H2O at 300 °C was found to produce local epitaxial growth [(001) Ge//(001) ZrO2 and [100] Ge//[100] ZrO2] without a distinct interfacial layer, unlike the situation observed when ZrO2 is deposited using the same method on Si. Relatively large lattice mismatch (∼10%) between ZrO2 and Ge produced a high areal density of interfacial misfit dislocations. Large hysteresis (>200 mV) and high frequency dispersion were observed in capacitance–voltage measurements due to the high density of interface states. However, a low leakage current density, comparable to values obtained on Si substrates, was observed with the same capacitance density regardless of the high defect density. © 2003 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Observation of domain walls in PbZr0.2Ti0.8O3 thin film using scanning nonlinear dielectric microscopy

K. Matsuura, Y. Cho, and R. Ramesh

Appl. Phys. Lett. 83, 2650 (2003); http://dx.doi.org/10.1063/1.1609252 (3 pages) | Cited 11 times

Online Publication Date: 23 September 2003

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Using scanning nonlinear dielectric microscopy (SNDM), we measured the linear dielectric constant of a domains (c axis in the plane of the film) and c domains (c axis perpendicular to the film surface) in PbZr0.2Ti0.8O3 (PZT) thin film to confirm that the dielectric constant of the a domain is higher than that of the c domain. We observed 90° a–c domain walls and 180° c–c domain walls and found that, experimentally, the 180° c–c domain wall was smaller than the 90° a–c domain wall. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
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