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27 Jun 2005

Volume 86, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 263107 (2005); http://dx.doi.org/10.1063/1.1952585 (3 pages)

B. Yang, M. S. Marcus, D. G. Keppel, P. P. Zhang, Z. W. Li, B. J. Larson, D. E. Savage, J. M. Simmons, O. M. Castellini, M. A. Eriksson, and M. G. Lagally
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Interfacial and electrical characteristics of Al2O3 gate dielectric on fully depleted SiGe on insulator

Zengfeng Di, Miao Zhang, Weili Liu, Qinwo Shen, Suhua Luo, Zhitang Song, Chenglu Lin, Anping Huang, and Paul K. Chu

Appl. Phys. Lett. 86, 262102 (2005); http://dx.doi.org/10.1063/1.1957109 (3 pages) | Cited 4 times

Online Publication Date: 21 June 2005

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The interfacial and electrical characteristics of as-deposited or annealed A2O3 gate dielectric films grown on fully depleted SiGe-on-insulator are investigated. An interfacial layer composed of SiOx and GeOx is observed in the as-grown film. The interfacial silicate formation is effectively suppressed by GeOx formation. However, GeOx is reduced to Ge and extensive silicate formation occurs after annealing. The formation of silicate and disappearance of GeOx after annealing leads to a decrease in the density of the interfacial states.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness

Effect of duty cycle on plasma parameters in the pulsed dc magnetron argon discharge

Sang-Hun Seo, Jung-Hwan In, Hong-Young Chang, and Jeon-Geon Han

Appl. Phys. Lett. 86, 262103 (2005); http://dx.doi.org/10.1063/1.1946900 (3 pages) | Cited 12 times

Online Publication Date: 21 June 2005

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The time-resolved probe measurements of the plasma parameters and the electron energy distribution function are carried out in a unipolar pulsed dc magnetron argon discharge. The cathode target is driven by the 20 kHz midfrequency unipolar dc pulses at three operating modes, such as constant voltage, constant power, and constant current with the duty cycles ranging from 10% to 90%. It is observed that as the duty cycle is reduced, the electron temperature averaged during the pulse-on period rapidly increases irrespective of the operating mode although the average electron density strongly depends on the operating mode. The comparison of the measured electron energy distribution functions shows that the electron heating during the pulse-on period becomes efficient in the pulse operation with short duty cycle, which is closely related to the deep penetration of the high-voltage sheath into the bulk during the pulse-on period.
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52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties
52.50.Gj Plasma heating by particle beams
52.40.Kh Plasma sheaths

Molecular-beam epitaxy of p-type m-plane GaN

M. McLaurin, T. E. Mates, and J. S. Speck

Appl. Phys. Lett. 86, 262104 (2005); http://dx.doi.org/10.1063/1.1977204 (3 pages) | Cited 28 times

Online Publication Date: 22 June 2005

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We report on the plasma-assisted molecular-beam epitaxy of Mg-doped (10math0) GaN on (10math0) 6H–SiC. Secondary ion mass spectroscopy measurements show the incorporation of Mg into the GaN films with an enhanced Mg incorporation under N-rich conditions relative to Ga-rich growth. Transport measurements of Mg-doped layers grown under Ga-rich conditions show hole concentrations in the range of p = 1×1018 to p = 7×1018 cm−3 and a dependence between hole concentration and Mg beam equivalent pressure. An anisotropy in in-plane hole mobilities was observed, with the hole mobility parallel to [11math0] being higher than that parallel to [0001] for the same hole concentration. Mobilities parallel to [11math0] were as high as ∼ 11.5 cm2/Vs (at p ∼ 1.8×1018 cm−3).
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.77.Dq Plasma-based ion implantation and deposition
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Resonant localized donor state above the conduction band minimum in InN

L. H. Dmowski, J. A. Plesiewicz, T. Suski, Hai Lu, W. Schaff, M. Kurouchi, Y. Nanishi, L. Konczewicz, V. Cimalla, and O. Ambacher

Appl. Phys. Lett. 86, 262105 (2005); http://dx.doi.org/10.1063/1.1977212 (3 pages) | Cited 12 times

Online Publication Date: 23 June 2005

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We have studied the pressure dependence of Hall electron concentration and mobility in degenerated, not intentionally doped InN samples. The results obtained for a whole set of samples with electron concentrations from 5.4×1017 cm−3 to 3.3×1018 cm−3 consistently reveal the existence of a localized donor type state, resonant with the conduction band. Its energy position is estimated to be about 80–90 meV above the bottom of the conduction band. This donor state is not the only source of electrons in these not intentionally doped samples and can be entirely populated and hidden in samples with very high electron concentrations.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.61.Ey III-V semiconductors
73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena
72.20.My Galvanomagnetic and other magnetotransport effects
71.55.Eq III-V semiconductors

Study of low-temperature crystallization of amorphous Si films obtained using ferritin with Ni nanoparticles

Hiroya Kirimura, Yukiharu Uraoka, Takashi Fuyuki, Mitsuhiro Okuda, and Ichiro Yamashita

Appl. Phys. Lett. 86, 262106 (2005); http://dx.doi.org/10.1063/1.1954872 (3 pages) | Cited 29 times

Online Publication Date: 23 June 2005

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A polycrystalline silicon thin film with a high crystallinity was obtained using ferritin with a Ni core (7 nm), which enabled us to precisely control the density and position of the nucleus for crystal growth. The core density of ferritin adsorbed on the amorphous silicon surface was controlled in the range from 109 cm−2 to 1011 cm−2. Crystal growth was performed at 550 °C in N2. Crystallinity or grain size strongly depended on Ni core density. Polycrystalline silicon film with the average grain size of 3 μm and a high crystallinity was obtained at a low Ni atom density of 1012 cm−2.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
68.47.Fg Semiconductor surfaces
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Strongly temperature-dependent free-energy barriers measured in a polycrystalline semiconductor

David L. Young and Richard S. Crandall

Appl. Phys. Lett. 86, 262107 (2005); http://dx.doi.org/10.1063/1.1977211 (3 pages) | Cited 8 times

Online Publication Date: 24 June 2005

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We measured temperature-dependent changes in free-energy barriers for emission of holes and electrons from metastable defects in polycrystalline CuIn1−xGaxSe2 using transient capacitance techniques. The free-energy barrier for holes increases by 17 meV, while the barrier for electrons decreases by 30 meV as the temperature increases from 380 to 400 K. The usual relation between thermal emission time and activation energy is reversed in this temperature range (we find a shorter emission time for the larger activation energy). Large entropy changes of +15 kB and −21 kB for the electron and hole emission, respectively, are calculated using transition-rate theory. These entropy terms in the free energy barrier account for the temperature dependences and the emission time inversion.
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65.40.G- Other thermodynamical quantities
71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Photographic surveying of minority carrier diffusion length in polycrystalline silicon solar cells by electroluminescence

Takashi Fuyuki, Hayato Kondo, Tsutomu Yamazaki, Yu Takahashi, and Yukiharu Uraoka

Appl. Phys. Lett. 86, 262108 (2005); http://dx.doi.org/10.1063/1.1978979 (3 pages) | Cited 78 times

Online Publication Date: 24 June 2005

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Photographic surveying of the minority carrier diffusion length distribution in polycrystalline silicon solar cells was proposed. Light emission from the cell under the forward bias was captured by a charge coupled device camera. We have found that the intensity distribution of light emission clearly agreed with the mapping of minority carrier diffusion length in polycrystalline silicon active layers. The emission intensity had a one-to-one relationship with the minority carrier diffusion length, which yielded a semiquantitative analysis method of the diffusion length mapping and the detection of the deteriorated areas.
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84.60.Jt Photoelectric conversion
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.60.Fi Electroluminescence

Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors

R. W. I. de Boer, A. F. Stassen, M. F. Craciun, C. L. Mulder, A. Molinari, S. Rogge, and A. F. Morpurgo

Appl. Phys. Lett. 86, 262109 (2005); http://dx.doi.org/10.1063/1.1984093 (3 pages) | Cited 58 times

Online Publication Date: 24 June 2005

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We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches 0.3 cm2/V s in both materials. The highest mobility for electrons is observed for iron-phthalocyanines and is approximately one order of magnitude lower. Our measurements indicate that these values are limited by extrinsic contact effects due to the transistor fabrication and suggest that considerably higher values for the electron and hole mobility can be achieved in these materials.
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85.30.Tv Field effect devices

Monte Carlo study of vertical electron transport in GaN/AlGaN heterostructures

A. Reklaitis

Appl. Phys. Lett. 86, 262110 (2005); http://dx.doi.org/10.1063/1.1968434 (3 pages) | Cited 5 times

Online Publication Date: 24 June 2005

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The dc and large-signal ac vertical electron transport in the double-barrier GaN/AlGaN heterostructures are studied by Monte Carlo simulations. It is found that the current-voltage characteristic of the GaN/AlGaN diode is asymmetric due to polarization charges at GaN/AlGaN interfaces. On the contrary, the calculated capacitance-voltage characteristic is nearly symmetric in respect to the shifted bias voltage. The capacitance-voltage characteristic shows that GaN/AlGaN heterostructures are promising candidates for the design of efficient varactor diodes. Study of the large-signal ac electron transport predicts that GaN/AlGaN varactors are capable to operate as frequency triplers in the near-terahertz frequency range.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes
84.32.Tt Capacitors
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Noise subtraction in antiferromagnetically coupled magnetic recording media

Andreas Moser, Natacha F. Supper, Andreas Berger, David T. Margulies, and Eric E. Fullerton

Appl. Phys. Lett. 86, 262501 (2005); http://dx.doi.org/10.1063/1.1949725 (3 pages) | Cited 1 time

Online Publication Date: 20 June 2005

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We have investigated, both experimentally and theoretically, the media noise of antiferromagnetically coupled (AFC) recording media. In particular, we have studied how the lower-layer magnetic properties affect the media noise of the composite system. We find that AFC media perform well even for intrinsically noisy lower layers, such as soft-magnetic Co or CoCr layers with high intergranular exchange coupling. To understand the experimentally observed behavior, we propose a new concept of noise subtraction in AFC magnetic systems, in which the noise of the lower layer is anticorrelated to and subtracts from the noise in the upper layers and acts as a low-pass magnetic filter of the magnetization state in the upper layer.
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75.50.Ss Magnetic recording materials
75.50.Ee Antiferromagnetics
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Broadband spin dynamics of Permalloy rings in the circulation state

Xiaobin Zhu, Marek Malac, Zhigang Liu, Hui Qian, Vitali Metlushko, and Mark R. Freeman

Appl. Phys. Lett. 86, 262502 (2005); http://dx.doi.org/10.1063/1.1957107 (3 pages) | Cited 10 times

Online Publication Date: 20 June 2005

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The spin dynamics of the remanent state of circulating magnetization in micrometer-scale Permalloy rings is studied by broadband ferromagnetic resonance. A number of resonance modes are observed, depending upon the geometries of coupling the transient excitation to the ring and of magneto-optically monitoring the response. The two dominant modes involve precession with uniform phase around the ring, or in a circularly antisymmetric standing wave pattern with two nodes. Other magnetic normal modes are also excited but with much smaller amplitude.
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75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Bb Fe and its alloys

Anisotropy dependence of irreversible switching in Fe/SmCo and FeNi/FePt exchange spring magnet films

Joseph E. Davies, Olav Hellwig, Eric E. Fullerton, J. S. Jiang, S. D. Bader, G. T. Zimányi, and Kai Liu

Appl. Phys. Lett. 86, 262503 (2005); http://dx.doi.org/10.1063/1.1954898 (3 pages) | Cited 40 times

Online Publication Date: 21 June 2005

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Magnetization reversal in exchange-spring magnet films has been investigated by a first-order reversal curve (FORC) technique and vector magnetometry. In Fe∕epitaxial-SmCo films, the reversal proceeds by a reversible rotation of the Fe soft layer, followed by an irreversible switching of the SmCo hard layer. The switching fields are clearly manifested by separate steps in both longitudinal and transverse hysteresis loops, as well as sharp boundaries in the FORC distribution. In FeNi∕polycrystalline-FePt films, particularly with thin FeNi, the switching fields are masked by the smooth and step-free major loop. However, the FORC diagram still displays a distinct onset of irreversible switching and transverse hysteresis loops exhibit a pair of peaks, whose amplitude is larger than the maximum possible contribution from the FeNi layer alone. This suggests that the FeNi and FePt layers reverse in a continuous process via a vertical spiral. The successive versus continuous rotation of the soft∕hard layer system is primarily due to the different crystal structure of the hard layer, which results in different anisotropies.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Jk Magnetization reversal mechanisms

Direct observation of the magnetic-field-induced entropy change in Gd5(SixGe1−x)4 giant magnetocaloric alloys

Fèlix Casanova, Amílcar Labarta, Xavier Batlle, Francisco J. Pérez-Reche, Eduard Vives, Lluís Mañosa, and Antoni Planes

Appl. Phys. Lett. 86, 262504 (2005); http://dx.doi.org/10.1063/1.1968431 (3 pages) | Cited 27 times

Online Publication Date: 21 June 2005

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Direct observation of the entropy change in a first-order phase transition is obtained by using a differential scanning calorimeter in which the transition is field-induced under the application of an external magnetic field. This procedure enables direct evaluation of the magnetocaloric effect in materials showing first-order magnetostructural phase transitions. Results for Gd5(SixGe1−x)4 giant magnetocaloric alloys are reported. Calorimetric curves sweeping the field through the transition reveal a unusual increase of the entropy change with cycling. This increase is accounted for by considering both the structural and magnetic contributions to the total entropy change.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
65.40.G- Other thermodynamical quantities

Room-temperature epitaxial growth of ferromagnetic Fe3Si films on Si(111) by facing target direct-current sputtering

T. Yoshitake, D. Nakagauchi, T. Ogawa, M. Itakura, N. Kuwano, Y. Tomokiyo, T. Kajiwara, and K. Nagayama

Appl. Phys. Lett. 86, 262505 (2005); http://dx.doi.org/10.1063/1.1978984 (3 pages) | Cited 22 times

Online Publication Date: 24 June 2005

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Ferromagnetic Fe3Si thin films with an extremely smooth surface morphology can be epitaxially grown on Si(111) at room temperature by facing target direct-current sputtering. The epitaxial relationship is Fe3Si(111)‖Si(111) with Fe3Si[1math0]‖Si[math10]. By the application of the extinction rule of x-ray diffraction, the generated Fe3Si was confirmed to possess a B2 structure and not a DO3 one. The film showed a saturation magnetization value of 960 emu/cm3, which was slightly lower than that of bulk DO3-Fe3Si. It was observed that the magnetization easy axis was along the [1math0] direction in the film plane.
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75.50.Dd Nonmetallic ferromagnetic materials
81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
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Dynamics of domain inversion in LiNbO3 poled using topographic electrode geometries

Benjamin F. Johnston and Michael J. Withford

Appl. Phys. Lett. 86, 262901 (2005); http://dx.doi.org/10.1063/1.1952574 (3 pages)

Online Publication Date: 22 June 2005

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We report results of an investigation studying the domain inversion kinetics of lithium niobate when electric field poling using laser-machined topographical electrodes. Inversion is shown to begin with a single nucleation spike and the domains evolve in a unique fashion governed by the topographical structure. We also demonstrate control of the resulting domain widths when poling using this technique. The results presented have implications for rapid prototyping of chirped and aperiodic domain structures in lithium niobate.
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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.Ej Polarization and depolarization
42.70.-a Optical materials

Visible-ultraviolet spectroscopic ellipsometry of lead zirconate titanate thin films

Hosun Lee, Youn Seon Kang, Sang-Jun Cho, Bo Xiao, Hadis Morkoç, and Tae Dong Kang

Appl. Phys. Lett. 86, 262902 (2005); http://dx.doi.org/10.1063/1.1968432 (3 pages) | Cited 4 times

Online Publication Date: 22 June 2005

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We measured pseudodielectric functions in the visible-ultraviolet spectral range of Pb(ZrxTi1−x)O3 (x = 0.2, 0.56, 0.82) (PZT) grown on platinized silicon substrate using the sol-gel method and also on (0001) sapphire using radio frequency sputtering method. Using a parametric optical constant model, we estimated the dielectric functions of the PZT thin films. Taking the second derivative of the fitted layer dielectric functions and using the standard critical point model, we determined the parameters of the critical points. In the second derivative spectra, the lowest bandgap energy peak near 4 eV is fitted as a double peak for annealed PZTs associated with the perovskite phase. As-grown PZTs have mainly pyrochlore phase and the lowest bandgap is fitted as a single peak. We compared the bandgap energies with literature values.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
78.40.Ha Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
77.22.Ch Permittivity (dielectric function)
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.40.Gh Other heat and thermomechanical treatments

“Dielectric relaxor” behavior of electroactive fluorinated polymers

Chen Ang and Zhi Yu

Appl. Phys. Lett. 86, 262903 (2005); http://dx.doi.org/10.1063/1.1948518 (3 pages) | Cited 8 times

Online Publication Date: 22 June 2005

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The dielectric spectra of poly(vinylidene fluoride-trifluoroethylene) copolymers and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymers are studied in a wide temperature and frequency range with electric field. It is found that the dominant relaxation process displays a peculiar characteristic—a “dielectric relaxor” behavior, rather than a “ferroelectric relaxor” behavior reported in the current literature; furthermore, we show the experimental observation that the existence of nanometer scale crystals embedded in an amorphous matrix is the base of the dielectric relaxor behavior and high electroactive performance in these polymers.
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77.84.Jd Polymers; organic compounds
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
77.22.Gm Dielectric loss and relaxation
77.22.Ej Polarization and depolarization

Manganese-modified BiScO3–PbTiO3 piezoelectric ceramic for high-temperature shear mode sensor

Shujun Zhang, Richard E. Eitel, Clive A. Randall, Thomas R. Shrout, and Edward F. Alberta

Appl. Phys. Lett. 86, 262904 (2005); http://dx.doi.org/10.1063/1.1968419 (3 pages) | Cited 47 times

Online Publication Date: 22 June 2005

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The bismuth-based perovskite solid solution (100−x)BiScO3−xPbTiO3 (BSPT) was investigated for use at temperatures up to 400 °C and above. The high-temperature resistivity, together with dielectric and piezoelectric behaviors of the shear mode for manganese-modified BSPT ceramics near the morphotropic phase boundary composition were studied. The resistivity and time constant were found to be 3×107 Ω cm and 0.08 s, respectively, at 450 °C for modified BSPT66. The dielectric constant Κ11T and dielectric loss were found to be 1112 and 1%, respectively, at room temperature, showing a Curie temperature at 468 °C. The electromechanical coupling factor k15 was calculated to be 61%, staying nearly constant up to 440 °C, expanding the temperature usage range significantly. The properties indicate that the modified BSPT66 material is a promising candidate for high-temperature shear sensor applications.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.B- Phase transitions and Curie point

Enhanced tetragonality in (x)PbTiO3-(1−x)Bi(Zn1/2Ti1/2)O3 and related solid solution systems

Matthew R. Suchomel and Peter K. Davies

Appl. Phys. Lett. 86, 262905 (2005); http://dx.doi.org/10.1063/1.1978980 (3 pages) | Cited 97 times

Online Publication Date: 23 June 2005

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The solid solutions (x)PbTiO3-(1−x)Bi(Zn1/2Ti1/2)O3, (x)PbTiO3-(1−x)Bi(Zn1/2Zn1/2)O3, and (x)PbTiO3-(1−x)Bi(Zn1/2Sn1/2)O3, have been examined by x-ray diffraction, dielectric measurements, and thermal analysis. Unlike most PbTiO3-based solid solutions, these systems show enhanced tetragonality with substitution for PbTiO3. In particular, the (x)PbTiO3-(1−x)Bi(Zn1/2Ti1/2)O3 system exhibits a high c/a ratio of 1.11 for x = 0.60. Accordingly, the Curie temperature (TC) also increases, exceeding 700 °C at the same composition. It is proposed that PbTiO3-Bi(B)O3-type solid solutions which contain only highly polarizable cations on the B site are likely to exhibit similar enhancements in tetragonality and TC.
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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
61.66.Fn Inorganic compounds

Chemical phase transitions of the HfO2/SiON/Si nanolaminate by high-temperature thermal treatments in NO and O2 ambient

J. H. Oh, Y. Park, K.-S. An, Y. Kim, J. R. Ahn, J. Y. Baik, and C. Y. Park

Appl. Phys. Lett. 86, 262906 (2005); http://dx.doi.org/10.1063/1.1957110 (3 pages) | Cited 3 times

Online Publication Date: 23 June 2005

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Temperature-dependent chemical phase transitions of the HfO2/SiON/Si(100) nanolaminate in O2 and NO ambient have been investigated using high-resolution photoemission spectroscopy. Hf 4f, Si 2p, O 1s, and N 1s photoemission spectra were measured after annealing the nanolaminate at a temperature between 750 and 1150 °C. These spectra show that the chemical phase transitions of the nanolaminate strongly dependend on the ambient gases. The nanolaminate in an O2 ambient is stable below 750 °C but the HfO2 and SiON layers dissociate by producing Hf silicides above 950 °C. In contrast, the nanolaminate in NO ambient does not transit into Hf silicides up to 1050 °C. Interestingly, the HfO2 and SiON layers transforms into HfOxNy and SiNx layers, respectively, with a high thermal stability, where the HfOxNy layers are a high-k dielectric material and the SiNx layers work as a barrier against both Si and O diffusion
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81.05.Mh Cermets, ceramic and refractory composites
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
64.70.K- Solid-solid transitions
81.40.Gh Other heat and thermomechanical treatments
79.60.Jv Interfaces; heterostructures; nanostructures
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.35.Fx Diffusion; interface formation

Identification of a determining parameter for resistive switching of TiO2 thin films

Christina Rohde, Byung Joon Choi, Doo Seok Jeong, Seol Choi, Jin-Shi Zhao, and Cheol Seong Hwang

Appl. Phys. Lett. 86, 262907 (2005); http://dx.doi.org/10.1063/1.1968416 (3 pages) | Cited 146 times

Online Publication Date: 23 June 2005

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Electric-pulse-induced resistive switching of 43 nm thick TiO2 thin films grown by metalorganic chemical vapor deposition was studied by current-voltage (I-V) and constant voltage-time measurements. The resistance ratio between the two stable states of the film constitutes approximately 1000. The allowed current level and voltage step width during the sweep mode I-V measurements influenced switching parameters, such as the switching voltage, time before switching, and resistance values. However, it was clearly observed that the power imparted to the film controlled mainly switching. The required power for successful switching was almost invariant irrespective of other measurement variables.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
73.61.Ng Insulators
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Overpoling-induced property degradation in Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals of near-morphotropic phase boundary compositions

M. Shanthi, K. H. Hoe, C. Y. H. Lim, and L. C. Lim

Appl. Phys. Lett. 86, 262908 (2005); http://dx.doi.org/10.1063/1.1957114 (3 pages) | Cited 11 times

Online Publication Date: 24 June 2005

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Overpoling phenomenon has been observed in flux-grown Pb(Mg1/3Nb2/3)O3–(31–32)%PbTiO3 single crystals when poled above 0.4 kV/mm at room temperature. This leads to increased property variations at intermediate poling fields (0.6–0.8 kV/mm) and to the degradation of piezoelectric properties at high poling fields ( ≥ 1.0 kV/mm). In comparison, both PMN–28%PT and PMN–30%PT crystal compositions are resistant to overpoling, of which PMN–30%PT exhibits superior dielectric and piezoelectric properties with KT ≈ 7500–9000, d33 ≈ 2200–2500 pC/N, and d31 ≈ 1100–1400 pC/N. The electromechanical coupling factors (k33 = 0.90–0.94; k31 = 0.48–0.55, and kt = 0.58–0.62) are relatively insensitive to the poling field and crystal composition.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ch Permittivity (dielectric function)

Effective electromechanical moduli of ferroelectric ceramics with fiber textures

Y. C. Zhou, J. Liu, and J. Y. Li

Appl. Phys. Lett. 86, 262909 (2005); http://dx.doi.org/10.1063/1.1952584 (3 pages) | Cited 5 times

Online Publication Date: 24 June 2005

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In this letter, we report the predictions on the effective piezoelectric coefficients and electromechanical coupling factors of ferroelectric ceramics BaTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) with various fiber textures, including [001], [011], and [111], using a two-scale micromechanical model that accounts for microstructural phenomena at both domain and grain levels. It was observed that for BaTiO3 the [011] texture is optimal with highest d31 and d33, while for PMN-PT [001] texture is optimal despite the fact that [011]-oriented single-crystalline PMN-PT has higher d32 than that of [001]-oriented PMN-PT single crystal. In fact, [011]-textured PMN-PT ceramics have much smaller piezoelectric coefficients d32 and d33 than does [011]-oriented PMN-PT single crystal. It is also noted that [001]-textured BaTiO3 and PMN-PT ceramics have even higher electromechanical coupling factor k31 than that of [001]-oriented single crystals.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity
61.72.-y Defects and impurities in crystals; microstructure
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Nanoscale polarization relaxation in a polycrystalline ferroelectric thin film: Role of local environments

V. Nagarajan, S. Aggarwal, A. Gruverman, R. Ramesh, and R. Waser

Appl. Phys. Lett. 86, 262910 (2005); http://dx.doi.org/10.1063/1.1977183 (3 pages) | Cited 20 times

Online Publication Date: 24 June 2005

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In this letter, we report on the study of nanoscale polarization relaxation phenomena in polycrystalline PbZr0.4Ti0.6O3 films. Piezoresponse force microscopy (PFM) images of the as-grown sample reveal grains with a range of contrast, from fully white to gray to fully black. It is shown that this local change in the contrast (magnitude) of the piezoresponse from grain to grain can be attributed to the crystallographic orientation within each grain. PFM-based relaxation experiments show that the rate of relaxation is different for each grain, furthermore it is strongly dependent on the tilt of individual crystallographic orientation with respect to the polar axis. Strongly tilted away nonpolar axis grains show a much stronger decay of the polarization compared to polar axis-oriented grains. Therefore, for an ensemble of grains under a common top electrode, the relaxation events would first take place in grains, which are nonpolar axis oriented.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
77.80.-e Ferroelectricity and antiferroelectricity
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Abnormal temperature dependence of conductance of single Cd-doped ZnO nanowires

Q. H. Li, Q. Wan, Y. G. Wang, and T. H. Wang

Appl. Phys. Lett. 86, 263101 (2005); http://dx.doi.org/10.1063/1.1954878 (3 pages) | Cited 12 times

Online Publication Date: 20 June 2005

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Positive temperature coefficient of resistance is observed on single Cd-doped ZnO nanowires. The current along the nanowire increases linearly with the bias and saturates at large biases. The conductance is greatly enhanced either by ultraviolet illumination or infrared illumination. However, the conductance decreases with increasing temperature, in contrast to the reported temperature behavior either for ZnO nanostructures or for CdO nanoneedles. The increase of the conductance under illumination is related to surface effect and the decrease with increasing temperature to bulk effect. These results show that Cd doping does not change surface effect but affects bulk effect. Such a bulk effect could be used to realize on-chip temperature-independent varistors.
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73.63.Nm Quantum wires
73.61.Ga II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
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