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26 Jun 2006

Volume 88, Issue 26, Articles (26xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 261107 (2006); http://dx.doi.org/10.1063/1.2213912 (3 pages)

Stanley S. Hong, Berthold K. P. Horn, Dennis M. Freeman, and Michael S. Mermelstein
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Study of pore structure and stability in porous low-k interconnects using electrolyte voltammetry

D. M. Meng, N. L. Michael, Choong-Un Kim, and Young-Joon Park

Appl. Phys. Lett. 88, 261911 (2006); http://dx.doi.org/10.1063/1.2218060 (3 pages) | Cited 2 times

Online Publication Date: 28 June 2006

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This letter presents a step-mode voltammetry method which uses ion diffusivity to characterize pore structure in both dense and porous low dielectric constant materials (low k) in patterned interconnect structures. Findings reveal that the intramolecular space in dense low k acts like a small physical pore network. It is determined that electrolyte ions can migrate through such space in dense low k, but with higher activation energy than in porous low k or the bulk solution, 0.31 eV vs 0.18–0.19 eV. Also, this study finds that the pores in ultralow k are not stable but can either coalesce or collapse depending on stress conditions.
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61.43.Gt Powders, porous materials
85.40.Ls Metallization, contacts, interconnects; device isolation
77.55.-g Dielectric thin films
82.45.Rr Electroanalytical chemistry
66.30.H- Self-diffusion and ionic conduction in nonmetals
77.22.Ch Permittivity (dielectric function)

Facets evolution and surface electrical properties of nonpolar m-plane ZnO thin films

J. Zúñiga-Pérez, V. Muñoz-Sanjosé, E. Palacios-Lidón, and J. Colchero

Appl. Phys. Lett. 88, 261912 (2006); http://dx.doi.org/10.1063/1.2218320 (3 pages) | Cited 20 times

Online Publication Date: 28 June 2006

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ZnO thin films have been grown along the nonpolar [10math0] direction by metal organic vapor phase epitaxy. The ZnO (10math0) surface develops well defined facets. The orientation of the topographic normals reveals that the inclination angle of the facets increases as thicker films are considered, attaining a maximum value of about 28.4°. This angle corresponds to {10math1}- and {10mathmath}-type facets. The origin of this faceting is discussed in terms of thermodynamic stability and kinetics arguments. The surface electrical properties of the facets have been studied by Kelvin probe microscopy, showing that the surface has different contact potential domains that alternate along the polar [0001] direction.
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81.05.Dz II-VI semiconductors
73.25.+i Surface conductivity and carrier phenomena
68.47.Fg Semiconductor surfaces
73.61.Ga II-VI semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology

Thermal stability and its prediction of bulk metallic glass systems

Mingxu Xia, Shuguang Zhang, Jianguo Li, and Chaoli Ma

Appl. Phys. Lett. 88, 261913 (2006); http://dx.doi.org/10.1063/1.2218324 (3 pages) | Cited 9 times

Online Publication Date: 28 June 2006

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We report a linear relationship between the thermal stability (ΔTx) and the amorphous formation enthalpy (ΔHam) of typical bulk metallic glasses (BMGs). The value of the slope of ΔTx vs ΔHam reflects the sensitivity of thermal stability to composition and the sign of the slope implies whether the local atomic structure of amorphous phase is similar to that of primary crystalline phase. A positive slope suggests a similarity between them and vice versa. We also demonstrate that the thermal stability can be fastly assessed and predicted by ΔHam at less cost using Ti53Cu15Ni18.5Al7M3Si3B0.5 (M = Hf,Sc,Ta,Nb) BMGs.
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61.43.Fs Glasses
82.60.Cx Enthalpies of combustion, reaction, and formation

Thermal conductivity enhancement in water-in-FC72 nanoemulsion fluids

B. Yang and Z. H. Han

Appl. Phys. Lett. 88, 261914 (2006); http://dx.doi.org/10.1063/1.2218325 (3 pages) | Cited 19 times

Online Publication Date: 28 June 2006

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The strategy of adding solid particles to fluids for improving thermal conductivity has been pursued for nearly a century. In this work, a concept of using liquid nanodroplets for enhancing thermal conductivity has been developed and was demonstrated in water-in-FC72 suspensions, called “nanoemulsion fluids.” The thermal conductivity of FC72 is found to be increased by up to 52% for a nanoemulsion fluid containing 12 vol % water nanodroplets of radius 9.8 nm. Such types of nanoemulsion fluids possess long-term stability and can be mass produced because of no needs for solid nanoparticles. The development of nanoemulsion fluids would open a direction for thermal fluids studies.
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66.25.+g Thermal conduction in nonmetallic liquids
82.70.Kj Emulsions and suspensions

Real time multicomponent echo particle image velocimetry technique for opaque flow imaging

Hairong Zheng, Lingli Liu, Logan Williams, Jean R. Hertzberg, Craig Lanning, and Robin Shandas

Appl. Phys. Lett. 88, 261915 (2006); http://dx.doi.org/10.1063/1.2216875 (3 pages) | Cited 13 times

Online Publication Date: 29 June 2006

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This letter reports on a contrast-based ultrasonic particle imaging technique (echo PIV) for measuring multicomponent velocity vectors in opaque flows with excellent temporal (up to 0.5 ms) and spatial (up to 0.4 mm) resolution. Ultrasound contrast microbubbles are used as flow tracers, and digitally acquired rf data are converted into B-mode images for PIV analysis. Here, velocity fields from various flow patterns (including rotating and transient vortex flows) that are difficult to measure using other opaque flow methods such as ultrasound Doppler or magnetic resonance imaging are measured using echo PIV. This nonintrusive technique should be a promising addition to opaque flow diagnostics.
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47.80.Jk Flow visualization and imaging
43.58.-e
43.60.Lq
47.32.Ef Rotating and swirling flows

Stress control structures for microelectromechanical systems using structural mechanics approach

T. Krupenkin, V. A. Lifton, A. Tran, J. Vuillemin, and D. W. Carr

Appl. Phys. Lett. 88, 261916 (2006); http://dx.doi.org/10.1063/1.2218771 (3 pages) | Cited 1 time

Online Publication Date: 30 June 2006

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A method of stress control in microelectromechanical systems (MEMS) devices is presented that consists of creating counterbalancing structures to position stressed layers at the neutral plane of the device, eliminating the bending momentum acting on the device. Upon metallization, many MEMS elements such as silicon membranes show substantial bow under the stress developed as a result of the difference in the thermal expansion coefficients of a metal and silicon. The proposed membranes with the counterbalancing structures remain flat in the entire test temperature range (25–150 °C). The method gives material-independent solution to stress-induced curvature problems in a variety of ultrathin devices.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
65.40.De Thermal expansion; thermomechanical effects
85.40.Ls Metallization, contacts, interconnects; device isolation

Optical properties of inorganic AgSb recording thin film

Y. H. Fang, P. C. Kuo, P. W. Chen, Wei-Chih Hsu, C. Y. Chou, and T. H. Wu

Appl. Phys. Lett. 88, 261917 (2006); http://dx.doi.org/10.1063/1.2218774 (3 pages) | Cited 1 time

Online Publication Date: 30 June 2006

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50 nm Ag1−xSbx (x = 10.8–25.5) thin films were prepared by magnetron sputtering. Thermal analysis shows that the phase change occurs around 250 °C. The optical property analysis show that the as-deposited Ag80.9Sb19.1 films have high reflectivity of about 62%–73%. After heat treatment at 300 °C, the contrast of Ag80.9Sb19.1 film is 12.5%–17% for wavelengths between 400 and 800 nm. Dynamic test shows that using the Ag80.9Sb19.1 film as the memory layer of write once optical disk, a carrier-to-noise ratio of about 45 dB can be achieved at λ = 657 nm, numerical aperture of 0.65, and a linear velocity of 3.5 m/s.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
81.40.Gh Other heat and thermomechanical treatments
42.79.Vb Optical storage systems, optical disks

Characteristic fragment size distributions in dynamic fragmentation

Fenghua Zhou, Jean-François Molinari, and K. T. Ramesh

Appl. Phys. Lett. 88, 261918 (2006); http://dx.doi.org/10.1063/1.2216892 (3 pages) | Cited 6 times

Online Publication Date: 30 June 2006

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The one-dimensional fragmentation of a dynamically expanding ring (Mott’s problem) is studied numerically to obtain the fragment signatures under different strain rates. An empirical formula is proposed to calculate an average fragment size. Rayleigh distribution is found to describe the statistical properties of the fragment populations.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Higher lying conduction band in GaN and AlN probed by photoluminescence spectroscopy

N. Nepal, K. B. Nam, J. Li, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 88, 261919 (2006); http://dx.doi.org/10.1063/1.2217160 (3 pages) | Cited 2 times

Online Publication Date: 30 June 2006

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Photoluminescence spectroscopy has been employed to study the band edge emissions in GaN and AlN epilayers up to 800 K. Two distinctive activation processes have been observed in both GaN and AlN. The first process occurring below Tt = 325 K (Tt = 500 K) for GaN (AlN) is due to the activation of free excitons to free carriers, whereas the second occurring above Tt with an activation energy of 0.29 eV (0.3 eV) for GaN (AlN) is believed to be associated with a higher lying conduction band (Γ3) at about 0.3 eV above the conduction band minimum (Γ1). An emission line at about 0.29 eV above the dominant transition in GaN was also observed at 700 K, corroborating the assignment of Γ3. The values of Tt are a direct measure of the onset temperature at which free excitons dissociate into free carriers.
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71.20.Nr Semiconductor compounds
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena

Tailored emission color synthesis using microfacet quantum wells consisting of nitride semiconductors without phosphors

M. Funato, T. Kotani, T. Kondou, Y. Kawakami, Y. Narukawa, and T. Mukai

Appl. Phys. Lett. 88, 261920 (2006); http://dx.doi.org/10.1063/1.2217259 (3 pages) | Cited 28 times

Online Publication Date: 30 June 2006

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A color synthesis based on InGaN/GaN quantum wells (QWs) grown on GaN microfacets formed by regrowth on SiO2 mask stripes is demonstrated. The microfacet structure is composed of (0001), {11math2}, and {11math0} planes, and the InGaN well thickness and composition are spatially inhomogeneous due to the diffusion of the adatoms among the facets. These properties allow microfacet QWs, which, for example, emit yellow from the (0001) facet and blue from the {11math2} facet, to be fabricated, of which the luminescence appears white due to the additive color mixing. Using a mask pattern that consists of regions with and without stripes, the emissions from the microfacet QWs and from planar QWs are synthesized to produce the desired apparent output colors.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
78.67.De Quantum wells
78.55.Cr III-V semiconductors
68.65.Fg Quantum wells
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
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Effect of point defect and Mn concentration in time-resolved differential reflection in GaMnAs

Shin Kim, Eunsoon Oh, J. U. Lee, D. S. Kim, S. Lee, and J. K. Furdyna

Appl. Phys. Lett. 88, 262101 (2006); http://dx.doi.org/10.1063/1.2216108 (3 pages) | Cited 4 times

Online Publication Date: 26 June 2006

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We measured the transmission spectra and the time-resolved differential reflectivity ΔR in Ga1−xMnxAs for x ⩽ 0.05 for several excitation wavelengths. The sign of ΔR in Ga1−xMnxAs (x = 0.015 and x = 0.03) was negative for photon energy larger than band gap at room temperature. The negative component of ΔR was explained by defect induced absorption and/or the reduction of exciton bleaching, rather than by the change in density of near band edge states associated with Mn incorporation. For Ga0.95Mn0.05As, absorption edge broadening was observed in the transmission spectra and the induced absorption effect was reduced by the screening of Mn local potential by photocarriers.
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75.50.Pp Magnetic semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.66.Fd III-V semiconductors
71.20.Nr Semiconductor compounds
75.50.Dd Nonmetallic ferromagnetic materials
61.72.J- Point defects and defect clusters

Effect of oxygen plasma treatment on reduction of contact resistivity at pentacene/Au interface

Woong-Kwon Kim and Jong-Lam Lee

Appl. Phys. Lett. 88, 262102 (2006); http://dx.doi.org/10.1063/1.2218044 (3 pages) | Cited 16 times

Online Publication Date: 27 June 2006

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We report the reduction of contact resistivity between Au and pentacene by O2 plasma treatment. Contact resistance dramatically reduced from 5.65 to 0.22 MΩ cm by the treatment. O2 plasma treatment transformed Au to AuOx, increasing the surface energy from 45.1 to 71.5 mJ/m2. Molecular adsorption geometry of pentacene on AuOx changed from a planar structure to an upright type, improving crystallinity and molecular packing. Thus, defects and traps at the interface were reduced, decreasing the contact resistance between Au and pentacene.
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73.40.Cg Contact resistance, contact potential
52.77.-j Plasma applications
68.35.Md Surface thermodynamics, surface energies

p-type behavior in nominally undoped ZnO thin films by oxygen plasma growth

Y. J. Zeng, Z. Z. Ye, W. Z. Xu, J. G. Lu, H. P. He, L. P. Zhu, B. H. Zhao, Y. Che, and S. B. Zhang

Appl. Phys. Lett. 88, 262103 (2006); http://dx.doi.org/10.1063/1.2217165 (3 pages) | Cited 34 times

Online Publication Date: 28 June 2006

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We report on intrinsic p-type ZnO thin films by plasma-assisted metal-organic chemical vapor deposition. The optimal results give a resistivity of 12.7 Ω cm, a Hall mobility of 2.6 cm2/V s, and a hole concentration of 1.88×1017 cm−3. The oxygen concentration is increased in the intrinsic p-type ZnO, compared with the n-type layer. Two acceptor states, with the energy levels located at 160 and 270 meV above the valence band maximum, are identified by temperature-dependent photoluminescence. The origin of intrinsic p-type behavior has been ascribed to the formation of zinc vacancy and some complex acceptor center.
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81.05.Dz II-VI semiconductors
73.61.Ga II-VI semiconductors
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.66.Hf II-VI semiconductors

Alternative precursor metal-organic chemical vapor deposition of InGaAs/GaAs quantum dot laser diodes with ultralow threshold at 1.25 μm

A. Strittmatter, T. D. Germann, Th. Kettler, K. Posilovic, U. W. Pohl, and D. Bimberg

Appl. Phys. Lett. 88, 262104 (2006); http://dx.doi.org/10.1063/1.2218059 (3 pages) | Cited 6 times

Online Publication Date: 28 June 2006

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Laser diodes based on InGaAs quantum dots (QDs) operating at 1250 nm with ultralow threshold current densities of 66 A/cm2, transparency current densities of 10 A/cm2 per quantum dot layer, and high internal quantum efficiencies of 94% have been realized using alternative precursor metal-organic chemical vapor deposition. Photoluminescence of the active QD stacks clearly indicates the requirement of varying growth parameters for subsequently deposited QD layers. The excellent performance of the QD lasers was obtained by adjusting the number of stacked QD layers to a limit given by the In content of the InGaAs strain-reducing layers grown on the QDs and individual durations of the growth interruption after deposition for each QD layer.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors

Effects of As and Mn doping on microstructure and electrical conduction in ZnO films

K. Lord, T. M. Williams, D. Hunter, K. Zhang, J. Dadson, and A. K. Pradhan

Appl. Phys. Lett. 88, 262105 (2006); http://dx.doi.org/10.1063/1.2217257 (3 pages) | Cited 11 times

Online Publication Date: 29 June 2006

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We report the synthesis of epitaxial As-doped ZnO and Mn-doped (ZnAs)O films by pulsed-laser deposition technique. The grain size in (ZnAs)O films decreases from 40 to less than 10 nm upon Mn doping, illustrating that Mn acts as a potential catalyst to create nanosize grains. Temperature dependent electrical resistance shows metal-insulator transition and metal-semiconductor transition (MST) at 165 and 115 K, respectively, in (ZnAs)O, although Mn doping suppresses MST completely. Both ionization efficiency on oxygen vacancies and percolation of charge carriers may be responsible for such transitions. In addition, electrical conduction in these films shows strong aging effects.
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73.61.Ga II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.60.+g Mixed conductivity and conductivity transitions
61.72.J- Point defects and defect clusters
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging

Thermoelectric properties of doped titanium disulfides

Edward E. Abbott, Joseph W. Kolis, Nathan D. Lowhorn, William Sams, Apparao Rao, and Terry M. Tritt

Appl. Phys. Lett. 88, 262106 (2006); http://dx.doi.org/10.1063/1.2217190 (3 pages) | Cited 3 times

Online Publication Date: 30 June 2006

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We report herein the doping of titanium disulfide (TiS2) with the pnictides (Pn): P, As, and Sb. The incorporation of these pnictides into titanium disulfide (TiS2−xPnx) is performed at extremely low concentrations (x ∼ 0.2%). The effects on the electronic transport of titanium disulfide by doping with arsenic is quite profound, reducing the resistivity and thermopower to 0.2 mΩ cm and −35 μV/K at 300 K, respectively, from 1.8 mΩ cm and −170 μV/K at 300 K for the parent compound TiS2. For a wide range of thermopower values we find that the thermopower (α) of these doped titanium disulfides is linearly related to the infrared reflectivity minimum and can be correlated by the experimentally determined proportionality of λ = −0.0457α, where λ is the wavelength of the minimum.
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72.20.Pa Thermoelectric and thermomagnetic effects
61.72.S- Impurities in crystals
78.30.Hv Other nonmetallic inorganics
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Effects of magnetic substrates on ac losses of YBa2Cu3O7 films in perpendicular ac magnetic fields

Masaki Suenaga and Qiang Li

Appl. Phys. Lett. 88, 262501 (2006); http://dx.doi.org/10.1063/1.2218305 (3 pages) | Cited 15 times

Online Publication Date: 27 June 2006

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Effects of a magnetic substrate on the ac losses of superconducting films were investigated by measuring the losses for octagonal disks of an YBa2Cu3O7 layer on a magnetic Ni–5 at. % W substrate in perpendicular ac magnetic fields at 20 Hz and 77 K. At low fields, the losses depended on ac magnetic field amplitude B and film thickness t as ∝B3/t instead of ∝B4/t3 for a superconducting film on a nonmagnetic substrate. These results are described by considering the formation of a virtual infinite stack of superconducting films due to the magnetic mirror effect.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.72.-h Cuprate superconductors

Double-side superconducting MgB2 films for microwave and electronic applications

Li-ping Chen, Li-li Ding, Qing-rong Feng, Guang-cheng Xiong, Yun-fei Wang, Sheng Luo, Xue-qiang Zhang, and Yu-sheng He

Appl. Phys. Lett. 88, 262502 (2006); http://dx.doi.org/10.1063/1.2216900 (3 pages) | Cited 4 times

Online Publication Date: 28 June 2006

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Double-side superconducting MgB2 films have been grown on double-side polished sapphire substrates by using hybrid physical-chemical vapor deposition method. The zero resistance temperatures TC(0)>37 K and the critical current densities JC(5 K,0 T)>3×106 A/cm2 have been achieved for both sides. In the first 8.73 G MgB2 microstrip resonator fabricated by a double-side film, an unloaded Q value of 3400 at 11 K was obtained corresponding to surface resistance of 1.2 mΩ for the MgB2/Al2O3 interface. By simply using a sapphire substrate with two polished holes, superconducting connection has been achieved for the double-side MgB2 film. The results show potential applications for the superconducting MgB2 films in microwave and electronic devices.
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74.78.-w Superconducting films and low-dimensional structures
74.25.F- Transport properties
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.25.Sv Critical currents
74.25.N- Response to electromagnetic fields

High tunnel magnetoresistance in fully epitaxial magnetic tunnel junctions with a full-Heusler alloy Co2Cr0.6Fe0.4Al thin film

Takao Marukame, Takayuki Ishikawa, Ken-Ichi Matsuda, Tetsuya Uemura, and Masafumi Yamamoto

Appl. Phys. Lett. 88, 262503 (2006); http://dx.doi.org/10.1063/1.2217166 (3 pages) | Cited 51 times

Online Publication Date: 28 June 2006

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Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with a Co-based full-Heusler alloy Co2Cr0.6Fe0.4Al (CCFA) thin film, whose composition was close to the stoichiometric one, and a MgO tunnel barrier. Cross-sectional high-resolution transmission electron microscope observations indicated that all layers of the CCFA/MgO/Co50Fe50 MTJ layer structure were grown epitaxially and were single crystalline. The microfabricated CCFA/MgO/Co50Fe50 MTJs exhibited high tunnel magnetoresistance (TMR) ratios of 90% at room temperature and 240% at 4.2 K. A high tunneling spin polarization of 0.79 at 4.2 K was obtained for the epitaxial CCFA films from the TMR ratios.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Np Metals and alloys
75.47.Lx Magnetic oxides
72.25.Mk Spin transport through interfaces
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys

Detection of 0.5 THz radiation from intrinsic Bi2Sr2CaCu2O8 Josephson junctions

I. E. Batov, X. Y. Jin, S. V. Shitov, Y. Koval, P. Müller, and A. V. Ustinov

Appl. Phys. Lett. 88, 262504 (2006); http://dx.doi.org/10.1063/1.2214157 (3 pages) | Cited 35 times

Online Publication Date: 28 June 2006

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We report the detection of electromagnetic radiation at about 500 GHz from current-biased intrinsic Bi2Sr2CaCu2O8 single crystal Josephson junctions. We used two silicon lenses to quasioptically couple radiation from our samples to an integrated superconducting heterodyne receiver. The estimated maximum Josephson radiation power which reached the receiver antenna was about 1 pW. We attribute the observed radiation to individual Josephson junctions of the stack and discuss a possibility of the phase locking of a larger number of junctions.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.25.Cp Josephson devices

Low power scaling using parallel coupling for toggle magnetic random access memory

David W. Abraham and D. C. Worledge

Appl. Phys. Lett. 88, 262505 (2006); http://dx.doi.org/10.1063/1.2217236 (3 pages) | Cited 5 times

Online Publication Date: 29 June 2006

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Toggle-switched magnetic random access memory devices offer wide write margins and robustness against thermally activated switching but are as yet unproven regarding the feasibility of scaling down from present sizes with acceptable write currents. We present a strategy for reducing switching fields by using parallel coupling between the two magnetic free layers, in contrast to the usual antiferromagnetic coupling previously discussed. Combined with the proper free layer magnetic material and offset fields from a carefully imbalanced pinned layer, we present experimental verification of toggling of 130 nm diameter magnetic tunnel junctions at fields of less than 50 Oe.
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85.75.Dd Magnetic memory using magnetic tunnel junctions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
84.30.Sk Pulse and digital circuits

Large room temperature magnetization in nanocrystalline zinc ferrite thin films

Murtaza Bohra, Shiva Prasad, Naresh Kumar, D. S. Misra, S. C. Sahoo, N. Venkataramani, and R. Krishnan

Appl. Phys. Lett. 88, 262506 (2006); http://dx.doi.org/10.1063/1.2217253 (3 pages) | Cited 28 times

Online Publication Date: 29 June 2006

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Zinc ferrite films were deposited on fused quartz substrate at different temperatures using pulsed laser ablation (PLA) and rf sputtering. X-ray diffraction indicated that all the films were single phase ZnFe2O4 with grain growing in the range of 8–80 nm with substrate temperature. The nanocrystalline films were found to be magnetic and the spontaneous magnetization showed a strong dependence on the grain size, dropping sharply for films with larger grains. A PLA thin film deposited in vacuum at 500 °C exhibited a room temperature magnetization value of 5560 G.
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75.50.Gg Ferrimagnetics
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
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Noncontact electrical metrology of Cu/low-k interconnect for semiconductor production wafers

Vladimir V. Talanov, André Scherz, and Andrew R. Schwartz

Appl. Phys. Lett. 88, 262901 (2006); http://dx.doi.org/10.1063/1.2216898 (3 pages) | Cited 4 times

Online Publication Date: 26 June 2006

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We have demonstrated a technique capable of in-line measurement of dielectric constant of low-k interconnect films on patterned wafers utilizing a test key of ∼ 50×50 μm2 in size. The test key consists of a low-k film backed by a Cu grid with >50% metal pattern density and <0.25 μm pitch, which is fully compatible with the existing dual-damascene interconnect manufacturing processes. The technique is based on a near-field scanned microwave probe and is noncontact, noninvasive, and requires no electrical contact to or grounding of the wafer under test. It yields <0.3% precision and ±2% accuracy for the film dielectric constant.
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85.40.Ls Metallization, contacts, interconnects; device isolation
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
77.55.-g Dielectric thin films
07.68.+m Photography, photographic instruments; xerography
77.22.Ch Permittivity (dielectric function)

Ferroelectricity in the Dion-Jacobson CsBiNb2O7 from first principles

Craig J. Fennie and Karin M. Rabe

Appl. Phys. Lett. 88, 262902 (2006); http://dx.doi.org/10.1063/1.2218040 (3 pages) | Cited 1 time

Online Publication Date: 26 June 2006

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We have studied ferroelectricity in Dion-Jacobson CsBiNb2O7 from first principles. Using group-theoretical analysis and first-principles density functional calculations of the total energy and phonons, we perform a systematic study of the energy surface around a paraelectric prototypic phase. Our results suggest that CsBiNb2O7 is a ferroelectric with a polarization of Ps = 40 μC cm−2. We propose further experiments to clarify this point.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
63.20.-e Phonons in crystal lattices
68.35.Md Surface thermodynamics, surface energies
77.22.Ej Polarization and depolarization

Surface scanning probe microscopy investigation of solution deposited BiFeO3 thin films

S. Habouti, C. Solterbeck, and M. Es-Souni

Appl. Phys. Lett. 88, 262903 (2006); http://dx.doi.org/10.1063/1.2212280 (3 pages) | Cited 6 times

Online Publication Date: 27 June 2006

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Thin films of the multiferroic perovskite-type oxide BiFeO3 were processed via solution deposition. The annealing schedule was chosen so as to give large and fine grained thin films. Microstructure, polarization, and dielectric properties are reported. It is shown that the large grained film is characterized by poor dielectric properties. Both microstructures show, however, poor polarization characteristics. Surface scanning potential microscopy reveals areas of high and low surface potentials in both specimens with a pronounced effect in the large grained films. It is thought that these areas are indirectly responsible for the poor polarization properties of the processed BiFeO3 films.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
81.40.Gh Other heat and thermomechanical treatments
68.37.-d Microscopy of surfaces, interfaces, and thin films
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