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23 Jun 2008

Volume 92, Issue 25, Articles (25xxxx)

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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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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

Tunneling atomic-force microscopy as a highly sensitive mapping tool for the characterization of film morphology in thin high-k dielectrics

Vasil Yanev, Mathias Rommel, Martin Lemberger, Silke Petersen, Brigitte Amon, Tobias Erlbacher, Anton J. Bauer, Heiner Ryssel, Albena Paskaleva, Wenke Weinreich, Christian Fachmann, Johannes Heitmann, and Uwe Schroeder

Appl. Phys. Lett. 92, 252910 (2008); http://dx.doi.org/10.1063/1.2953068 (3 pages) | Cited 24 times

Online Publication Date: 27 June 2008

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High-k dielectric layers (HfSixOy and ZrO2) with different film morphologies were investigated by tunneling atomic-force microscopy (TUNA). Different current distributions were observed for amorphous and nanocrystalline films by analyzing TUNA current maps. This even holds for crystalline layers where highly resolved atomic-force microscopy cannot detect any crystalline structures. However, TUNA enables the determination of morphology in terms of differences in current densities between nanocrystalline grains and their boundaries. The film morphologies were proven by high-resolution transmission electron microscopy. The investigations show TUNA as powerful current mapping tool for the characterization of morphology in thin high-k films on a nanoscale.
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68.55.J- Morphology of films
61.43.Er Other amorphous solids
61.46.Hk Nanocrystals
61.72.Mm Grain and twin boundaries
77.55.-g Dielectric thin films
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