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23 Jun 2008

Volume 92, Issue 25, Articles (25xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 254102 (2008); http://dx.doi.org/10.1063/1.2945893 (3 pages)

M. Trinker, S. Groth, S. Haslinger, S. Manz, T. Betz, S. Schneider, I. Bar-Joseph, T. Schumm, and J. Schmiedmayer
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Ductile Fe–Nb–B bulk metallic glass with ultrahigh strength

J. H. Yao, J. Q. Wang, and Y. Li

Appl. Phys. Lett. 92, 251906 (2008); http://dx.doi.org/10.1063/1.2949747 (3 pages) | Cited 31 times

Online Publication Date: 23 June 2008

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The authors report a simple Fe-based Fe71Nb6B23 ternary bulk metallic glass with a record high strength of 4.85 GPa as well as an appreciable compressive plastic strain of 1.6%. This finding is associated with the unique attribute of the alloying element Nb, which favors the formation of a networklike structure and holds high Poisson’s ratio. A fracture feature with a combination of vein pattern and nanoscale corrugations under compression is clearly characterized in this glass. The fractographic observations correlate well with the observed improvements in plasticity.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.43.Fs Glasses
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dj Poisson's ratio

Shaped graded materials with an apparent negative thermal conductivity

C. Z. Fan, Y. Gao, and J. P. Huang

Appl. Phys. Lett. 92, 251907 (2008); http://dx.doi.org/10.1063/1.2951600 (3 pages) | Cited 13 times

Online Publication Date: 24 June 2008

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Based on a first-principles approach, we exploit a class of shaped graded materials in which thermal energy is apparently controlled to transfer from a region of lower temperature to a region of higher temperature. This phenomenon, which is in contrast to our common intuition, is indicative of an apparent negative thermal conductivity (ANTC). Further analysis shows that the ANTC is related to a symmetric oscillation of paired thermal conductivities with specific gradation profiles, which are shown to satisfy a sum rule. Such shaped graded materials can serve as good candidates for thermal rectification.
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44.10.+i Heat conduction

Magneto-optical properties of transparent divalent iron phosphate glasses

Hirofumi Akamatsu, Koji Fujita, Shunsuke Murai, and Katsuhisa Tanaka

Appl. Phys. Lett. 92, 251908 (2008); http://dx.doi.org/10.1063/1.2952460 (3 pages) | Cited 9 times

Online Publication Date: 24 June 2008

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We have prepared glasses having xFeO⋅(100−x)P2O5 (mol %) (x = 50.0,54.0,57.1) compositions by melting under mild reducing condition and found that these glasses exhibit fairly high transmittance in the visible range and large Faraday effect at the wavelength of about 400 nm. 57Fe Mössbauer spectra confirm that almost all the iron ions are present as Fe2+ in the glasses. A spin glass transition is observed at low temperatures in the temperature dependence of magnetic susceptibility. Intense optical absorption in the ultraviolet and infrared wavelength ranges occurs by the charge transfer transition from O2− to Fe2+ and the intra-atomic d-d transition, respectively. The analysis on the wavelength dependence of the Faraday rotation angle using the Van Vleck–Hebb theory has revealed that the charge transfer transition contributes more significantly to the Faraday effect owing to the large effective transition probability, which is comparable to those reported for glasses containing 4f rare-earth ions. The magneto-optical figure of merit shows a maximum at around 380 nm.
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78.20.Ls Magneto-optical effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
75.50.Lk Spin glasses and other random magnets
75.30.Cr Saturation moments and magnetic susceptibilities

Activation and carrier mobility in high fluence B implanted germanium

S. Mirabella, G. Impellizzeri, A. M. Piro, E. Bruno, and M. G. Grimaldi

Appl. Phys. Lett. 92, 251909 (2008); http://dx.doi.org/10.1063/1.2949088 (3 pages) | Cited 19 times

Online Publication Date: 24 June 2008

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High doping regimes of B implanted Ge have been accurately characterized combining Hall effect technique and nuclear reaction analysis. Preamorphized Ge was implanted with B at 35 keV (spanning the 0.25–25×1020 B/cm3 concentration range) and recrystallized by solid phase epitaxy at 360 °C. The Hall scattering factor and the maximum concentration of active B resulted rH = 1.21 and ∼ 5.7×1020 B/cm3, respectively. The room-temperature carrier mobility was accurately measured, decreasing from ∼ 300 to 50 cm2/V s in the investigated dopant density, and a fitting empirical law is given. These results allow reliable evaluation for Ge application in future microelectronic devices.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Cw Elemental semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.uf Ge and Si

Extraction of ultraviolet emitting silicon species from strongly hydrogenated nanoporous silicon

V. Lysenko, V. Onyskevych, O. Marty, V. A. Skryshevsky, Y. Chevolot, and C. Bru-Chevallier

Appl. Phys. Lett. 92, 251910 (2008); http://dx.doi.org/10.1063/1.2948955 (3 pages) | Cited 4 times

Online Publication Date: 26 June 2008

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Ultraviolet emitting silicon species were extracted from strongly hydrogenated porous silicon nanostructures. Their photoluminescence spectra depend on size distribution of the species and can be tuned by centrifugation. Molecular structure of the extracted Si species is assumed to be very similar to some kinds of polysilanes which were theoretically described earlier by Allan et al. [Phys. Rev. B 48, 7951 (1993)]. Absence of photoluminescence signal coming from the polysilanes in the initial porous nanostructures is supposed to be due to the competitive absorption and to the energy transfer between the polysilanes and Si red emitting porous nanoparticles.
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78.55.Ap Elemental semiconductors
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.43.Gt Powders, porous materials

Latent heat investigation by photopyroelectric calorimetry

F. Mercuri, M. Marinelli, S. Paoloni, U. Zammit, and F. Scudieri

Appl. Phys. Lett. 92, 251911 (2008); http://dx.doi.org/10.1063/1.2951620 (3 pages) | Cited 10 times

Online Publication Date: 27 June 2008

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We report on an approach for photopyroelectric calorimetry enabling a frequency dependence detection of the specific heat and of the latent heat exchanged over first order transitions. It has been applied to the nematic-isotropic transition of 4-n-octyl-4′-cyanobiphenyl liquid crystal confined in a silica nanoparticles network, where the specific heat shows a double peak structure. The larger strain involved with the nematic nucleating over the low temperature peak induces a considerable lower latent heat than the one involved over the higher temperature peak. The frequency dependent measurements have shown a different dynamics of the nematic nucleating over the two peaks.
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61.30.-v Liquid crystals
65.20.-w Thermal properties of liquids
64.70.M- Transitions in liquid crystals
64.60.Q- Nucleation

Insight into the Raman shifts and optical absorption changes upon annealing polymer/fullerene solar cells

Je-Jung Yun, Jeffrey Peet, Nam-Sung Cho, Guillermo C. Bazan, Seung Joon Lee, and Martin Moskovits

Appl. Phys. Lett. 92, 251912 (2008); http://dx.doi.org/10.1063/1.2940205 (3 pages) | Cited 14 times

Online Publication Date: 27 June 2008

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Raman shifts and optical absorption spectra of bulk heterojunction films were measured to elucidate the origin of the optimum annealing parameters. A series of device optimization studies revealed 413 K to be the optimum annealing temperature, leading to a power conversion efficiency of 2.95%. The highest power conversion efficiency coincides with the highest peak in the UV-visible absorption and the lowest full width at half maximum of the –C=C– symmetric stretching signal in the Raman spectra. The changes observed in the vibronic shifts could be useful in obtaining information about the optimal performance and processing conditions for polymer optoelectronic devices.
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84.60.Jt Photoelectric conversion
78.40.-q Absorption and reflection spectra: visible and ultraviolet
78.30.-j Infrared and Raman spectra

Improved resonance characteristics of GaAs beam resonators by epitaxially induced strain

H. Yamaguchi, K. Kato, Y. Nakai, K. Onomitsu, S. Warisawa, and S. Ishihara

Appl. Phys. Lett. 92, 251913 (2008); http://dx.doi.org/10.1063/1.2952957 (3 pages) | Cited 10 times

Online Publication Date: 27 June 2008

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Micromechanical-beam resonators were fabricated using a strained GaAs film grown on relaxed In0.1Ga0.9As/In0.1Al0.9As buffer layers. The natural frequency of the fundamental mode was increased 2.5–4 times by applying tensile strain, showing good agreement with the model calculation assuming strain of 0.35% along the beam. In addition, the Q factor of 19 000 was obtained for the best sample, which is one order of magnitude higher than that for the unstrained resonator. This technique can be widely applied for improving the performance of resonator-based micro-/nanoelectromechanical devices.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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Two-dimensional electron gas insulation by local surface thin thermal oxidation in AlGaN/GaN heterostructures

Fabrizio Roccaforte, Filippo Giannazzo, Ferdinando Iucolano, Corrado Bongiorno, and Vito Raineri

Appl. Phys. Lett. 92, 252101 (2008); http://dx.doi.org/10.1063/1.2946657 (3 pages) | Cited 3 times

Online Publication Date: 24 June 2008

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In this letter, the physical effects of the local surface thin thermal oxidation on the current transport in AlGaN/GaN heterostructures are reported. Current-voltage measurements performed on appropriate test patterns demonstrated that a selective oxidation process at 900 °C enables the suppression of the current flow through the two-dimensional electron gas. The electrical insulation was achieved even though structural analysis showed that the formed oxide did not reach the depth of the AlGaN/GaN heterointerface. The combination of capacitance-voltage measurements with depth-resolved scanning capacitance microscopy enabled to correlate the electrical results to the doping and the compositional stability of the material during oxidation.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Mq Oxidation
61.72.uj III-V and II-VI semiconductors

Preparation and characterization of (001)- and (110)-oriented 0.6FeTiO3⋅0.4Fe2O3 films for room temperature magnetic semiconductors

Yusuke Takada, Makoto Nakanishi, Tatsuo Fujii, and Jun Takada

Appl. Phys. Lett. 92, 252102 (2008); http://dx.doi.org/10.1063/1.2951589 (3 pages) | Cited 3 times

Online Publication Date: 24 June 2008

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Thin films of ilmenite-hematite solid solution 0.6FeTiO3⋅0.4Fe2O3 were prepared on α-Al2O3 (001) and (110) single-crystalline substrates. The oxide phases formed in the thin films strongly depended on the oxygen partial pressure (PO2) during deposition. At PO2 = 1.3×10−3 Pa, regardless of thesubstrate orientation, well-ordered 0.6FeTiO3⋅0.4Fe2O3 films with Rmath symmetry were epitaxially formed. Large saturation magnetization at room temperature was observed in both (001)- and (110)-oriented films. The differences in the magnetization and electrical resistivity curves between the (001)- and (110)-oriented films indicated the anisotropic nature of 0.6FeTiO3⋅0.4Fe2O3.
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81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
68.55.J- Morphology of films
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
75.50.Gg Ferrimagnetics

Equal mobility of constituent cations in BaTiO3

Han-Ill Yoo, Chung-Eun Lee, Roger A. De Souza, and Manfred Martin

Appl. Phys. Lett. 92, 252103 (2008); http://dx.doi.org/10.1063/1.2951606 (3 pages) | Cited 1 time

Online Publication Date: 24 June 2008

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It is widely believed that in BaTiO3, Ba2+ cations are much more mobile than Ti4+ cations. Under a dc electric field, Ba cations are therefore expected at elevated temperatures to move at a faster rate to the cathode, leading to compositional demixing and eventually to decomposition of the BaTiO3. We have found that this is not the case. Overall mass transfer in BaTiO3 does occur but with no compositional demixing. This indicates that contrary to the general belief, Ba2+ and Ti4+ have the same electrochemical mobilities in BaTiO3. This suggests a common diffusion mechanism involving both cation sublattices.
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66.30.-h Diffusion in solids
82.45.-h Electrochemistry and electrophoresis

Electronic structure and optical properties of Nb-doped anatase TiO2

X. D. Liu, E. Y. Jiang, Z. Q. Li, and Q. G. Song

Appl. Phys. Lett. 92, 252104 (2008); http://dx.doi.org/10.1063/1.2949070 (3 pages) | Cited 20 times

Online Publication Date: 24 June 2008

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The electronic structure and optical properties of pure and Nb-doped TiO2 with anatase structure were calculated using local-density approximation based on the density-functional theory. For the undoped TiO2, the Fermi level locates in the band gap between the conduction band and valence band, while it moves into the conduction band and shows metal-like characteristic after Nb atom was introduced into the TiO2 supercell. The optical absorption coefficients for both compounds are very small in the visible light range. Our calculations provide electronic structure evidence that the Nb-doped anatase TiO2 is a new type transparent conducing metal.
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71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Inversion capacitance-voltage studies on GaAs metal-oxide-semiconductor structure using transparent conducting oxide as metal gate

T. Yang, Y. Liu, P. D. Ye, Y. Xuan, H. Pal, and M. S. Lundstrom

Appl. Phys. Lett. 92, 252105 (2008); http://dx.doi.org/10.1063/1.2953080 (3 pages) | Cited 7 times

Online Publication Date: 27 June 2008

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A systematic capacitance-voltage (C-V) study has been performed on GaAs metal-oxide-semiconductor (MOS) structures with atomic-layer-deposited Al2O3 as gate dielectrics and indium tin oxide (ITO) as the metal gate. The transparent conducting ITO gate allows homogeneous photoillumination on the whole MOS capacitance area, such that one can easily observe the low-frequency (LF) C-V and quasistatic C-V of GaAs at room temperature. The semiconductor capacitance effect on GaAs MOS devices has also been identified and insightfully discussed based on the obtained LF C-V curves. The semiconductor capacitance effect becomes more important for devices with high-mobility channel materials and aggressively scaled high-k gate dielectrics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
72.20.Fr Low-field transport and mobility; piezoresistance

Evidence for surface dipole modifications in In2O3-based transparent conductors

S. P. Harvey, T. O. Mason, C. Körber, Y. Gassenbauer, and A. Klein

Appl. Phys. Lett. 92, 252106 (2008); http://dx.doi.org/10.1063/1.2953435 (3 pages) | Cited 6 times

Online Publication Date: 27 June 2008

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Surface dipole modifications were identified for contamination-free In2O3-based transparent conducting oxides by ultraviolet photoelectron spectroscopy on both thin film and bulk ceramic specimens. In particular, heating in air was found to result in an increase in ionization potential and work function. The formation of surface dipoles may be related to the unique structure (crystal, defect) of bixbyite-based materials. These findings have important ramifications for the tuning of work functions in In2O3-based transparent conductors.
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73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.61.Ng Insulators
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Evidence for electromagnetic granularity in the polycrystalline iron-based superconductor LaO0.89F0.11FeAs

A. Yamamoto, J. Jiang, C. Tarantini, N. Craig, A. A. Polyanskii, F. Kametani, F. Hunte, J. Jaroszynski, E. E. Hellstrom, D. C. Larbalestier, R. Jin, A. S. Sefat, M. A. McGuire, B. C. Sales, D. K. Christen, et al.

Appl. Phys. Lett. 92, 252501 (2008); http://dx.doi.org/10.1063/1.2952195 (3 pages) | Cited 40 times

Online Publication Date: 23 June 2008

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The recently discovered oxypnictide superconductors are layered, low carrier density compounds with many similarities to the high-Tc cuprates. An important question is whether they also exhibit weak-coupling across randomly oriented grain boundaries. In this work we show considerable evidence for such weak coupling by study of the dependence of magnetization in bulk and powdered samples. Bulk sample magnetization curves show very little hysteresis while remanent magnetization shows almost no sample size dependence, even after powdering. We conclude that these samples exhibit substantial electromagnetic granularity on a scale approximating the grain size, though we cannot yet determine whether this is intrinsic or extrinsic.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)

Effect of γ precipitates on martensitic transformation and magnetic properties in aged Mn–Ni–Ga alloys

W. Cai, J. Zhang, Z. Y. Gao, and J. H. Sui

Appl. Phys. Lett. 92, 252502 (2008); http://dx.doi.org/10.1063/1.2943661 (3 pages) | Cited 2 times

Online Publication Date: 26 June 2008

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Multiple martensitic transformation peaks were observed from differential scanning calorimetry curves in aged Mn50Ni25Ga25 alloys in which transformation temperature varied with aging temperature. The magnetization and coercivity were enhanced as a result of aging above magnetic transition temperature. A maximum magnetization up to 54 emu/g and a magnetization difference between two phases of 28 emu/g was achieved in the alloy aged at 873 K. However, coercivity as large as 1.2 kOe was obtained in 573 K aged alloy, with a high saturation field, which can be understood in terms of domain wall pinning.
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81.30.Kf Martensitic transformations
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.40.-s Critical-point effects, specific heats, short-range order
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Domain wall motion in epitaxial Pb(Zr,Ti)O3 capacitors investigated by modified piezoresponse force microscopy

S. M. Yang, J. Y. Jo, D. J. Kim, H. Sung, T. W. Noh, H. N. Lee, J.-G. Yoon, and T. K. Song

Appl. Phys. Lett. 92, 252901 (2008); http://dx.doi.org/10.1063/1.2949078 (3 pages) | Cited 27 times

Online Publication Date: 23 June 2008

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We investigated the time-dependent domain wall motion of epitaxial PbZr0.2Ti0.8O3 capacitors 100 nm thick using modified piezoresponse force microscopy (PFM). We obtained successive domain evolution images reliably by combining the PFM with switching current measurements. We observed that domain wall speed (v) decreases with increases in domain size. We also observed that the average value of v, obtained under applied electric field (Eapp), showed creep behavior, i.e., 〈v〉 ∼ exp[−(E0/Eapp)μ] with an exponent μ of 0.9±0.1 and an activation field E0 of about 700 kV/cm.
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77.55.-g Dielectric thin films
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
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Formation of an oxide-free Ge/TiO2 interface by atomic layer deposition on brominated Ge

Pendar Ardalan, Evan R. Pickett, James S. Harris, Jr., Ann F. Marshall, and Stacey F. Bent

Appl. Phys. Lett. 92, 252902 (2008); http://dx.doi.org/10.1063/1.2951608 (3 pages) | Cited 7 times

Online Publication Date: 24 June 2008

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Atomic layer deposition (ALD) of titanium dioxide (TiO2) high-κ dielectric films on brominated Ge substrates using titanium tetrachloride and water has been studied. A strong temperature dependence was observed for the TiO2 deposition rate. An accelerated growth rate was measured for the first 15 ALD cycles at 300 °C; this effect is attributed to bromine desorption and resultant deposition on halide-free Ge. Results suggest that TiO2 films were deposited with no interfacial oxide layer at 300 °C. The films were in a crystalline anatase phase at 300 °C, and were amorphous when deposited at 100 °C.
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68.35.Fx Diffusion; interface formation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.55.-g Dielectric thin films
68.43.Nr Desorption kinetics

Interface phase and tuning of polarization in metal-ferroelectric junctions: A theoretical study

Matías Núñez and M. Buongiorno Nardelli

Appl. Phys. Lett. 92, 252903 (2008); http://dx.doi.org/10.1063/1.2948899 (3 pages) | Cited 3 times

Online Publication Date: 25 June 2008

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Using first principles calculations, we have studied how the control of the interface structure in metal-ferroelectric junctions can be used to tune the polarization of the ferroelectric film. Using a Pt/BaTiO3/Pt as a prototypical system, we show that the polarization of the oxide can be tuned by the introduction of an interface layer of a different metal and that this interface effect varies with the thickness of the ferroelectric film. These results can be easily interpreted in terms of the local electronic structure of the interface and provide a phenomenological criterion for choosing the metal intralayer in order to obtain the desired polarization.
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77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
73.40.Rw Metal-insulator-metal structures
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states

Microwave dielectric permittivity and photoluminescence of Eu2O3 doped laser heated pedestal growth Ta2O5 fibers

C. P. L. Rubinger, L. C. Costa, M. Macatrão, M. Peres, T. Monteiro, F. M. Costa, N. Franco, E. Alves, B. Z. Saggioro, M. R. B. Andreeta, and A. C. Hernandes

Appl. Phys. Lett. 92, 252904 (2008); http://dx.doi.org/10.1063/1.2952284 (2 pages) | Cited 2 times

Online Publication Date: 25 June 2008

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We report the microwave dielectric properties and photoluminescence of undoped and europium oxide doped Ta2O5 fibers, grown by laser heated pedestal growth technique. The effects of Eu2O3 doping (1–3 mol %) on the structural, optical, and dielectric properties were investigated. At a frequency of 5 GHz, the undoped material exhibits a dielectric permittivity of 21 and for Eu2O3 doped Ta2O5 samples it increases, reaching up to 36 for the highest doping concentration. Nevertheless, the dielectric losses maintain a very low value. For this wide band gap oxide, Eu3+ optical activation was achieved and the emission is observed up to room temperature. Thus, the transparency and high permittivity make this material promising for electronic devices and microwave applications.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
78.55.Hx Other solid inorganic materials
61.72.up Other materials
77.22.Gm Dielectric loss and relaxation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Deposition of sol-gel derived lead lanthanum zirconate titanate thin films on copper substrates

M. Narayanan, D.-K. Kwon, B. Ma, and U. Balachandran

Appl. Phys. Lett. 92, 252905 (2008); http://dx.doi.org/10.1063/1.2945887 (3 pages) | Cited 9 times

Online Publication Date: 25 June 2008

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Lead lanthanum zirconate titanate (PLZT) thin films were directly deposited on copper substrates by chemical solution deposition and crystallized at temperatures of ≥ 650 °C under low pO2 conditions. Although the crystallization conditions used are conducive for copper oxidation, a thin layer ( ∼ 115 nm) of PLZT was sufficient to protect the underlying copper from oxidation. Films exhibited well saturated hysteresis loops with remanent polarization ∼ 24 μC/cm2 and dielectric constants ∼ 730. Indirect evidence suggests that the oxygen vacancies created during the high temperature processing are responsible for the degradation of the electrical properties of these thin films. Techniques for avoiding this problem are proposed.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.A- Nucleation and growth
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
61.72.jd Vacancies

Pyrochlore-based oxides with small temperature coefficient of dielectric constant

P. Prabhakar Rao, K. Ravindran Nair, K. S. Sibi, and Peter Koshy

Appl. Phys. Lett. 92, 252906 (2008); http://dx.doi.org/10.1063/1.2943654 (3 pages) | Cited 4 times

Online Publication Date: 27 June 2008

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Pyrochlore based oxides with small temperature coefficient of dielectric constant (TCK) in Ca–RE–Ti–M–O (RE = Sm or Dy and M = Nb or Ta) system are reported. The 1 MHz dielectric constants of these oxides vary from 26 to 102. The TCK in the vicinity of room temperature (20 °C) dramatically decreases, from more than −200 for CaRETiMO7 to less than −3 ppm/°C in the solid solutions of CaRETiNbO7–CaRETiTaO7 phases. Rietveld analysis of the x-ray diffraction data establishes a cubic pyrochlore-type phase in the space group Fd3m (No. 227).
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77.22.Ch Permittivity (dielectric function)
61.66.Fn Inorganic compounds
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling

Growth and pyroelectric properties of high Curie temperature relaxor-based ferroelectric Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary single crystal

Ping Yu, Feifei Wang, Dan Zhou, Wenwei Ge, Xiangyong Zhao, Haosu Luo, Jinglan Sun, Xiangjian Meng, and Junhao Chu

Appl. Phys. Lett. 92, 252907 (2008); http://dx.doi.org/10.1063/1.2942378 (3 pages) | Cited 9 times

Online Publication Date: 27 June 2008

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To enhance the service temperature of relaxor-PbTiO3 pyroelectric single crystals, high quality ternary perovskite single crystal was grown by a modified Bridgman technique. Analyzed by x-ray fluorescence, the as-grown crystal is 0.41Pb(In1/2Nb1/2)O3–0.17Pb(Mg1/3Nb2/3)O3–0.42PbTiO3 [PIMNT(41/17/42)], which appears to be a tetragonal ferroelectric phase with relatively high Curie temperature of 253 °C. It exhibits the relative permittivity of 487 and low dielectric loss of 0.3% at 50 Hz and room temperature. The pyroelectric properties with a pyroelectric coefficient of 5.7×10−4 C/m2 K and a detectivity of 6.34×10−5 Pa−1/2 would satisfy the needs of operation as a high Curie temperature material. The results show that PIMNT crystal with better temperature stability, compared with the pure PMNT single crystals, is a good candidate as an infrared detector material.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.10.Fq Growth from melts; zone melting and refining
77.70.+a Pyroelectric and electrocaloric effects
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Achieving 1 nm capacitive effective thickness in atomic layer deposited HfO2 on In0.53Ga0.47As

K. Y. Lee, Y. J. Lee, P. Chang, M. L. Huang, Y. C. Chang, M. Hong, and J. Kwo

Appl. Phys. Lett. 92, 252908 (2008); http://dx.doi.org/10.1063/1.2952826 (3 pages) | Cited 20 times

Online Publication Date: 27 June 2008

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A capacitive effective thickness (CET) value of 1.0 nm has been achieved in atomic layer deposited (ALD) high κ dielectrics HfO2 on In0.53Ga0.47As/InP. The key is a short air exposure under 10 min between removal of the freshly grown semiconductor epilayers and loading to the ALD reactor. This has led to minimal formation of the interfacial layer thickness, as confirmed using x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The measured electrical characteristics of metal-oxide-semiconductor diodes of Au/Ti/HfO2(4.5 nm)/In0.53Ga0.47As showed a low leakage current density of 3.8×10−4 A/cm2 at VFB+1 V, which is about eight orders of magnitudes lower than that of SiO2 with the same CET. The capacitance-voltage curves show an overall κ value of 17–18, a nearly zero flatband shift, and an interfacial density of states Dit of 2×1012 cm−2 eV−1.
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73.40.Ty Semiconductor-insulator-semiconductor structures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Lp Transmission electron microscopy (TEM)

Interaction of SiC thermal oxidation by-products with SiO2

C. Radtke, F. C. Stedile, G. V. Soares, C. Krug, E. B. O. da Rosa, C. Driemeier, I. J. R. Baumvol, and R. P. Pezzi

Appl. Phys. Lett. 92, 252909 (2008); http://dx.doi.org/10.1063/1.2945643 (3 pages) | Cited 5 times

Online Publication Date: 27 June 2008

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We investigated oxygen incorporation and exchange during thermal growth of silicon oxide films on silicon carbide. This investigation was carried out in parallel with the thermal growth of silicon oxide films on silicon for comparison. We provide experimental evidence that oxidation by-products of silicon carbide out-diffuse and interact with the silicon oxide overlayer, incorporating C and O. This and other results are in sharp contrast to those obtained for silicon samples, constituting a key issue in the stability of any dielectric material used on silicon carbide.
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81.65.Mq Oxidation
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
66.30.-h Diffusion in solids
68.55.A- Nucleation and growth
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