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23 Jul 2012

Volume 101, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 043101 (2012); http://dx.doi.org/10.1063/1.4737152 (4 pages)

Toshiaki Tanigaki, Yoshikatsu Inada, Shinji Aizawa, Takahiro Suzuki, Hyun Soon Park, Tsuyoshi Matsuda, Akira Taniyama, Daisuke Shindo, and Akira Tonomura
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Direct physical evidence of mechanisms of leakage and equivalent oxide thickness reduction in metal-insulator-metal capacitors based on RuOx/TiOx/SrxTiyOz/TiN stacks

M. A. Pawlak, J. Swerts, M. Popovici, B. Kaczer, M.-S. Kim, W.-C. Wang, K. Tomida, B. Govoreanu, J. Delmotte, V. V. Afanas’ev, M. Schaekers, W. Vandervorst, and J. A. Kittl

Appl. Phys. Lett. 101, 042901 (2012); http://dx.doi.org/10.1063/1.4737871 (3 pages) | Cited 3 times

Online Publication Date: 23 July 2012

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We present direct physical evidence supporting the mechanisms we proposed to explain low leakage (Jg) and low equivalent oxide thickness (EOT) in RuOx/TiOx/Sr-rich SrxTiyOz(STO)/TiN metal-insulator-metal capacitors which achieve Jg = 10−7 A/cm2 (1 V) at 0.45 nm EOT: (1) healing of STO traps by O incorporation from RuOx during STO crystallization anneal for low leakage and (2) TiOx/Sr-rich STO intermixing during STO crystallization anneal resulting in a higher Ti-content, higher k-value STO layer for low EOT. Proof of oxygen incorporation into the STO layer from the RuOx electrode as well as of TiOx/STO intermixing were obtained by secondary ion mass spectrometry performed on samples fabricated using O18 for Ru oxidation. We also show excellent match between measured leakage vs. voltage and simulations of trap-assisted leakage with asymmetric trap profiles due to STO trap healing next to RuOx, further supporting our model.
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84.32.Tt Capacitors

Strongly coupled phase transition in ferroelectric/correlated electron oxide heterostructures

Lu Jiang, Woo Seok Choi, Hyoungjeen Jeen, Takeshi Egami, and Ho Nyung Lee

Appl. Phys. Lett. 101, 042902 (2012); http://dx.doi.org/10.1063/1.4738784 (4 pages)

Online Publication Date: 24 July 2012

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We fabricated ultrathin ferroelectric/correlated electron oxide heterostructures composed of the ferroelectric Pb(Zr0.2Ti0.8)O3 and the correlated electron oxide (CEO) La0.8Sr0.2MnO3 on SrTiO3 substrates by pulsed laser epitaxy. The hole accumulation in the ultrathin CEO layer was substantially modified by heterostructuring with the ferroelectric layer, resulting in an insulator-metal transition. In particular, our thickness dependent study showed that drastic changes in transport and magnetic properties were strongly coupled to the modulation of charge carriers by ferroelectric field effect, which was confined to the vicinity of the interface. Thus, our results provide crucial evidence that strong ferroelectric field effect control can be achieved in ultrathin (10 nm) heterostructures, yielding at least a 100 000-fold change in resistivity.
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71.30.+h Metal-insulator transitions and other electronic transitions
72.60.+g Mixed conductivity and conductivity transitions
73.40.Ns Metal-nonmetal contacts
77.80.bn Strain and interface effects
68.35.Ct Interface structure and roughness

Valence band offset at the amorphous hydrogenated boron nitride-silicon (100) interface

S. W. King, M. French, J. Bielefeld, M. Jaehnig, M. Kuhn, G. Xu, and B. French

Appl. Phys. Lett. 101, 042903 (2012); http://dx.doi.org/10.1063/1.4739474 (4 pages) | Cited 1 time

Online Publication Date: 24 July 2012

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In order to understand the fundamental behavior of various boron nitride heterostructure devices, we have utilized x-ray photoelectron spectroscopy to determine the valence band offset (VBO) present at interfaces formed by plasma enhanced chemical vapor deposition of hexagonal amorphous hydrogenated boron nitride (a-BN:H) on Si (100) substrates. For an a-BN:H/Si interface with some interfacial SiNx and SiBx bonding, we determined the valence band offset to be 1.9 ± 0.15 eV. The conduction band offset was likewise determined to be 2.2 ± 0.2 eV with a type I alignment.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Ea III-V semiconductors
81.05.Gc Amorphous semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.43.Dq Amorphous semiconductors, metals, and alloys

Local surface potential distribution and its relaxation in ferroelectric poly(vinylidenefluoride-co-trifluoroethylene) thin films

Hyunwoo Choi, Jongin Hong, and Kwangsoo No

Appl. Phys. Lett. 101, 042904 (2012); http://dx.doi.org/10.1063/1.4734870 (3 pages)

Online Publication Date: 25 July 2012

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Local surface potential distributions and their relaxation behavior in ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) thin films were investigated using Kelvin-probe force microscopy. All surface potentials were negative regardless of the sign of the applied voltage because of the intrinsic negative charges that originated from the self-aligned region of dipoles at the ferroelectric/electrode interface. Importantly, the intrinsic charges would have a remarkable influence on the reliability of written data.
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77.22.Gm Dielectric loss and relaxation
77.80.Fm Switching phenomena
77.84.Jd Polymers; organic compounds
68.55.am Polymers and organics
77.80.Jk Relaxor ferroelectrics
61.41.+e Polymers, elastomers, and plastics

Bipolar piezoelectric fatigue of Bi(Zn0.5Ti0.5)O3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 Pb-free ceramics

Eric A. Patterson and David P. Cann

Appl. Phys. Lett. 101, 042905 (2012); http://dx.doi.org/10.1063/1.4738770 (4 pages)

Online Publication Date: 26 July 2012

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The piezoelectric fatigue behavior of Pb-free ceramics based on solid solutions of Bi(Zn0.5Ti0.5)O3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 was characterized at 50 kV/cm after 106 bipolar cycles. Ferroelectric compositions containing 2.5% Bi(Zn0.5Ti0.5)O3 exhibited only minor losses in maximum strain (∼10%). In compositions with 5% Bi(Zn0.5Ti0.5)O3 that exhibit large electric field-induced strains, the electromechanical strain actually increased 4%, exhibiting essentially fatigue free behavior. This finding demonstrates that these materials have excellent potential for demanding high cycle applications such as microelectromechanical systems actuators.
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77.65.Ly Strain-induced piezoelectric fields
77.80.-e Ferroelectricity and antiferroelectricity
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.me Fatigue

Effects of Ca-substitution on structural, dielectric, and ferroelectric properties of Ba5SmTi3Nb7O30 tungsten bronze ceramics

Kun Li, Xiao Li Zhu, Xiao Qiang Liu, and Xiang Ming Chen

Appl. Phys. Lett. 101, 042906 (2012); http://dx.doi.org/10.1063/1.4739841 (4 pages) | Cited 1 time

Online Publication Date: 26 July 2012

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Effects of Ca-substitution on the crystal structure and dielectric properties were investigated for Ba5SmTi3Nb7O30 tungsten bronze ceramics. The tetragonal tungsten bronze structure in space group P4bm was determined in Ba4CaSmTi3Nb7O30 ceramics, which was the same for Ba5SmTi3Nb7O30. The c-axis off center displacement in both B1 and B2-sites for Ba5SmTi3Nb7O30 was slightly larger than that in BaCaSmTi3Nb7O30, while the distortion of Ti/Nb(2)O6 octahedra in Ba4CaSmTi3Nb7O30 was obviously suppressed compared with that in Ba5SmTi3Nb7O30. Though there were also two dielectric anomalies observed in Ba4CaSmTi3Nb7O30, the relaxor ferroelectric nature was changed to the normal ferroelectric one, and both the endothermal peak in differential scanning calorimetry curve and the significant thermal hysteresis of the phase transition confirmed the first order ferroelectric transition. These results indicated that the ferroelectric nature of Ba4CaSmTi3Nb7O30 was more close to that in Ba4Sm2Ti4Nb6O30, and it could be concluded that the ferroelectric nature in filled tungsten bronze ceramics was primarily dominated by the A-site occupation rather than B-site occupation.
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61.66.Fn Inorganic compounds
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.80.Jk Relaxor ferroelectrics
77.84.Ek Niobates and tantalates

Atomic-resolution chemical imaging of oxygen local bonding environments by electron energy loss spectroscopy

Julia A. Mundy, Qingyun Mao, Charles M. Brooks, Darrell G. Schlom, and David A. Muller

Appl. Phys. Lett. 101, 042907 (2012); http://dx.doi.org/10.1063/1.4737208 (5 pages) | Cited 4 times

Online Publication Date: 26 July 2012

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Electron energy loss spectroscopy on an aberration-corrected scanning transmission electron microscope was used to map the elemental composition and bonding in a thin film of the multiferroic LuFe2O4 with atomic resolution. A two-dimensional analysis of the fine structure of the O-K edge yielded distinct signals for the two inequivalent oxygen sites in the crystal. Comparison to an ab-initio simulation showed that these two components can be interpreted in terms of the differing hybridization of the O p orbitals to the Lu and Fe d orbitals, thus producing an atomic-resolution map of the local oxygen bonding environment.
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68.55.aj Insulators
77.55.Nv Multiferroic/magnetoelectric films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.20.Uv Electron energy loss spectroscopy

Multiferroic domain structure in orthorhombic multiferroics of cycloidal spin order: Phase field simulations

P. Chu, D. P. Chen, and J.-M. Liu

Appl. Phys. Lett. 101, 042908 (2012); http://dx.doi.org/10.1063/1.4739426 (4 pages)

Online Publication Date: 27 July 2012

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The multiferroic domains and their responses to external electric and magnetic fields in orthorhombic multiferroics of cycloidal spin order, taking nonmagnetic rare-earth manganites as examples, are investigated using a phase-field model based on the time-dependent Ginzburg-Landau equation and Monte Carlo simulation. The ferroelectric 180°-domain pattern with head-to-head/tail-to-tail domain wall along the b-axis, assigned to the in-plane ab-CS thin film, is revealed. The domain switching in response to both electric and magnetic fields is simulated, consistent with experiments. The magnetic origin for the 180° head-to-head/tail-to-tail domain walls is discussed.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
75.85.+t Magnetoelectric effects, multiferroics

Towards left-handed metamaterials using single-size dielectric resonators: The case of TiO2-disks at millimeter wavelengths

R. Yahiaoui, U.-C. Chung, C. Elissalde, M. Maglione, V. Vigneras, and P. Mounaix

Appl. Phys. Lett. 101, 042909 (2012); http://dx.doi.org/10.1063/1.4739498 (4 pages)

Online Publication Date: 27 July 2012

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We report a strong magnetic activity using an all-dielectric metamaterial based on Mie resonances, designed to work at millimeter wavelengths over the 30–70 GHz band. A good agreement was achieved between numerical simulations and experiment in the case of one meta-layer based on TiO2-disks, manufactured using a simple bottom-up approach. We also demonstrate through numerical simulations a negative refractive index within the same investigated metamaterial made of high dielectric permittivity single-size pellets. Choosing the suitable aspect-ratio of the metamaterial building blocks, a broadband magnetic response and a left-handed behavior are simultaneously obtained. This is a promising step towards innovative and complex electromagnetic functions, involving cheap and easy made metamaterials for millimeter wave applications.
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42.70.-a Optical materials
42.79.-e Optical elements, devices, and systems
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.15.Eq Optical system design
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