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20 Oct 2003

Volume 83, Issue 16, pp. 3233-3430

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 3159 (2003); http://dx.doi.org/10.1063/1.1617378 (3 pages)

Zheng Wei Pan, Sheng Dai, David B. Beach, and Douglas H. Lowndes
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Optoelectrical properties of four amorphous silicon thin-film transistors 200 dpi active-matrix organic polymer light-emitting display

Yongtaek Hong, Jeong-Yeop Nahm, and Jerzy Kanicki

Appl. Phys. Lett. 83, 3233 (2003); http://dx.doi.org/10.1063/1.1617372 (3 pages) | Cited 6 times

Online Publication Date: 15 October 2003

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We report on opto-electrical properties of a current-driven 200 dpi active-matrix organic polymer red light-emitting display (AM–PLED) based on four hydrogenated amorphous silicon thin-film transistor pixel electrode circuits. The AM–PLED luminance and effective light-emission efficiency were 30 cd/m2 and 0.3 cd/A, respectively, at the data current equal to 25 mA. The display electroluminescent spectrum has a peak located at and the full width at half maximum value of 644 and 95 nm, respectively, and Commission Internationale de l’Eclairage color coordinates of (0.66,0.33). © 2003 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Jb Light-emitting devices
85.30.Tv Field effect devices

Design, fabrication, and characterization of coupling-strength-controlled directional coupler based on two-dimensional photonic-crystal slab waveguides

Y. Sugimoto, Y. Tanaka, N. Ikeda, T. Yang, H. Nakamura, K. Asakawa, K. Inoue, T. Maruyama, K. Miyashita, K. Ishida, and Y. Watanabe

Appl. Phys. Lett. 83, 3236 (2003); http://dx.doi.org/10.1063/1.1619209 (3 pages) | Cited 17 times

Online Publication Date: 15 October 2003

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A directional coupler (DC) with a coupling-strength control defect (CCD) based on a two-dimensional photonic-crystal slab waveguide is numerically and experimentally studied. The structure consists of two parallel-coupled single-defect waveguides separated by a triple-line air-hole array, with some missing air holes in the middle of the triple line. Using a two-dimensional finite-difference time-domain method, a 50% coupler was designed and almost 50% coupling performance was experimentally confirmed at a wavelength of ∼ 1.3 μm with a coupling length of about 7 μm, about 1/3 in length as compared to the DC without the CCD.© 2003 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.82.-m Integrated optics
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Active silicon-based two-dimensional slab photonic crystal structures based on erbium-doped hydrogenated amorphous silicon alloyed with carbon

Yong-Seok Choi, Joo Yeon Sung, Se-Heon Kim, Jung H. Shin, and Yong-Hee Lee

Appl. Phys. Lett. 83, 3239 (2003); http://dx.doi.org/10.1063/1.1620687 (3 pages) | Cited 7 times

Online Publication Date: 15 October 2003

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Two-dimensional (2D) slab photonic crystals based on Er-doped hydrogenated amorphous silicon alloyed with carbon (a-Si:H:C) are proposed and realized. Freestanding and oxide-cladding slab structures are fabricated and compared. 2D slab active photonic crystal structures show enhanced extraction of the trivalent erbium ion (Er3+) luminescence independent of the pump intensity. Temperature-insensitive light extraction efficiency with negligible surface-related nonradiative recombination was experimentally observed. The maximum enhancement became eightfold in freestanding slab structures. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.55.Ap Elemental semiconductors
78.55.Qr Amorphous materials; glasses and other disordered solids

Evidence of second-order nonlinear susceptibility sign reversal in thermally poled samples

A. Kudlinski, Y. Quiquempois, H. Zeghlache, and G. Martinelli

Appl. Phys. Lett. 83, 3242 (2003); http://dx.doi.org/10.1063/1.1620673 (3 pages) | Cited 5 times

Online Publication Date: 15 October 2003

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Thin layers of silica have been removed from thermally poled samples using a hydrofluoric acid etching. After each etching, the second-harmonic signal generated within the remaining glass has been recorded by means of a Maker fringes experiment. Evidence of a sign reversal within the nonlinear distribution is pointed out for 10-min poled Infrasil™ samples. © 2003 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
81.65.Cf Surface cleaning, etching, patterning

Imaging of optical field confinement in ridge waveguides fabricated on very-small-aperture laser

Fang Chen, A. Itagi, J. A. Bain, D. D. Stancil, T. E. Schlesinger, L. Stebounova, G. C. Walker, and B. B. Akhremitchev

Appl. Phys. Lett. 83, 3245 (2003); http://dx.doi.org/10.1063/1.1621088 (3 pages) | Cited 34 times

Online Publication Date: 15 October 2003

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Optical field confinement in a ridge waveguide nanostructure (“C” aperture) designed for ultrahigh-density recording was observed using an apertureless near-field scanning optical microscope. The aperture was fabricated on a commercial edge-emitting semiconductor laser as the light source. High-contrast near-field images at both 1× and 2× lock-in detection frequencies were obtained. The emission patterns are in agreement with theoretical simulation of such structures. A 90 nm×70 nm full width half maximum spot size was measured and is comparable to the ridge width of the aperture. © 2003 American Institute of Physics.
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42.79.Vb Optical storage systems, optical disks
84.40.Az Waveguides, transmission lines, striplines
07.79.Fc Near-field scanning optical microscopes

Fabrication and characterization of high-quality waveguide-mode resonant optical filters

P. S. Priambodo, T. A. Maldonado, and R. Magnusson

Appl. Phys. Lett. 83, 3248 (2003); http://dx.doi.org/10.1063/1.1618930 (3 pages) | Cited 46 times

Online Publication Date: 15 October 2003

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Optical filters containing resonant waveguide gratings are designed and fabricated using low-loss, robust materials. The double-layer filters contain a silicon dioxide diffractive element on a hafnium dioxide waveguide deposited on a fused silica substrate. Noise-pattern formation is minimized by use of an antireflective absorption layer during holographic grating recording in photoresist. Subsequent fabrication steps include metallization, lift-off, and oxygen plasma etch to create a metal etch mask for final CF4 plasma etching of a surface-relief grating. Spectral characterization with a tunable laser shows that the resulting filter exhibits 90% efficiency, 1.2 nm linewidth, and low sidebands. © 2003 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers
42.40.Eq Holographic optical elements; holographic gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer

Bends and splitters for self-collimated beams in photonic crystals

Xiaofang Yu and Shanhui Fan

Appl. Phys. Lett. 83, 3251 (2003); http://dx.doi.org/10.1063/1.1621736 (3 pages) | Cited 96 times

Online Publication Date: 15 October 2003

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We present finite-difference time-domain studies for self-collimated beams in photonic crystal structures. Using a pulse propagation technique that eliminates the interference from the boundary of finite photonic crystal structures, we show that the self-collimation phenomena can occur within a relatively wide bandwidth. We also demonstrate near-perfect operation efficiencies over wide frequency ranges in bends and splitters constructed by simply truncating the photonic crystal. © 2003 American Institute of Physics.
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42.79.Ag Apertures, collimators
42.70.Qs Photonic bandgap materials
42.82.Et Waveguides, couplers, and arrays

Negative luminescence with 93% efficiency from midwave infrared HgCdTe diode arrays

W. W. Bewley, J. R. Lindle, I. Vurgaftman, J. R. Meyer, J. L. Johnson, M. L. Thomas, and W. E. Tennant

Appl. Phys. Lett. 83, 3254 (2003); http://dx.doi.org/10.1063/1.1621454 (3 pages) | Cited 10 times

Online Publication Date: 15 October 2003

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We have investigated the negative luminescence (NL) properties of an array of HgCdTe photodiodes (λco = 4.6 μm at 295 K) as a function of temperature and wavelength. The internal NL efficiency of ≈ 93% at λ = 4.0 μm is nearly independent of temperature in the 240–300 K range, and at 296 K corresponds to an apparent temperature reduction of 54 K. This is obtained at a reverse-bias saturation current density of only 0.13 A/cm2 at 296 K, which is attributable in part to an array geometry that reduces the influence of macroscopic defects. These observed NL performance characteristics are compatible with most of the requirements for applications such as cold shielding. © 2003 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors

Multiband subwavelength magnetic reflectors based on fractals

Lei Zhou, Weijia Wen, C. T. Chan, and Ping Sheng

Appl. Phys. Lett. 83, 3257 (2003); http://dx.doi.org/10.1063/1.1622122 (3 pages) | Cited 18 times

Online Publication Date: 15 October 2003

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We use theory and experiment to demonstrate that a composite material, consisting of a metallic planar fractal and a metal sheet separated by a thin dielectric layer, can reflect electromagnetic wave in-phase at a series of frequencies, with some of the corresponding wavelengths much longer than the reflector’s own size. We show that the physics is governed by a series of intrinsic magnetic resonances and can be well described by an effective-media of frequency-dependent permeability. © 2003 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
05.45.Df Fractals

Rapid measurement of surface acoustic wave velocity on single crystals using an all-optical adaptive scanning acoustic microscope

Y. Hong, S. D. Sharples, M. Clark, and M. G. Somekh

Appl. Phys. Lett. 83, 3260 (2003); http://dx.doi.org/10.1063/1.1621091 (3 pages) | Cited 3 times

Online Publication Date: 15 October 2003

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An experimental method has been developed to measure the phase velocity of laser-generated and detected surface acoustic waves. An optical grating produced by a spatial light modulator was imaged onto the sample surface to generate the ultrasound whose frequency and wave front were controlled electrically by tailoring the grating. When the grating period matched the surface acoustic wavelength, strong excition of the surface wave was observed. Thus, the wavelength and, thereby, the phase velocity were determined. We present results with this method that allow the phase velocity and the angular dispersion of the generalized surface wave as well as the pseudosurface wave on the (100) nickel and (111) silicon single crystals to be measured, with the precision of approximately 0.2%. Those factors affecting the measurement precision are discussed. © 2003 American Institute of Physics.
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68.35.Iv Acoustical properties
68.37.Tj Acoustic force microscopy
43.35.Yb Ultrasonic instrumentation and measurement techniques
42.79.Dj Gratings

Highly directive radiation from sources embedded inside photonic crystals

Irfan Bulu, Humeyra Caglayan, and Ekmel Ozbay

Appl. Phys. Lett. 83, 3263 (2003); http://dx.doi.org/10.1063/1.1623010 (3 pages) | Cited 34 times

Online Publication Date: 15 October 2003

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In this work, we have experimentally and theoretically studied the angular distribution of power emitted from a radiation source embedded inside a photonic crystal. Our results show that it is possible to obtain highly directive radiation sources operating at the band edge of the photonic crystal. Half power beam widths as small as 6° have been obtained. Our results also show that the angular distribution of power strongly depends on the frequency and on the size of the photonic crystal. © 2003 American Institute of Physics.
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42.72.-g Optical sources and standards
41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.70.Qs Photonic bandgap materials

Experimental verification of backward-wave phenomenon by observation of reflection at angles larger than 90° in an anisotropic medium

Yi-Jun Jen

Appl. Phys. Lett. 83, 3266 (2003); http://dx.doi.org/10.1063/1.1622120 (3 pages) | Cited 1 time

Online Publication Date: 15 October 2003

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Calcite with its principal axes coordinates at an angle of φ = 45° from its surface normal is used here to observe the anomalous reflection at the calcite/air interface. Light is incident from the lateral side of the crystal to yield an angle of reflection larger than 90°. The reflected backward wave behavior is detected by observing the direction in which the light exits the crystal. Reflectance is calculated according to the nonsymmetric reflection theory. © 2003 American Institute of Physics.
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42.25.Gy Edge and boundary effects; reflection and refraction
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Neutron emission from a fast plasma focus of 400 Joules

Patricio Silva, José Moreno, Leopoldo Soto, Lipo Birstein, Roberto E. Mayer, and Walter Kies

Appl. Phys. Lett. 83, 3269 (2003); http://dx.doi.org/10.1063/1.1621460 (3 pages) | Cited 46 times

Online Publication Date: 15 October 2003

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The neutron emission from a small and fast plasma focus operating in deuterium is presented. The system operates at low energy in the hundred of joules range (880 nF capacitor bank, 38 nH, 20–35 kV, 176–539 J, ∼ 300 ns current rise time). The neutrons were measured by means of a silver activation counter, and the total neutron yield versus deuterium gas filling pressure was obtained. For discharges operating at 30 kV charging voltage, the maximum neutron yield was (1.06±0.13)×106 neutrons per shot at 9 mbar. © 2003 American Institute of Physics.
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52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.59.Hq Dense plasma focus
52.25.Tx Emission, absorption, and scattering of particles

Discharge comparison of nonequilibrium atmospheric pressure Ar/O2 and He/O2 plasma jets

S. Wang, V. Schulz-von der Gathen, and H. F. Döbele

Appl. Phys. Lett. 83, 3272 (2003); http://dx.doi.org/10.1063/1.1615674 (3 pages) | Cited 65 times

Online Publication Date: 15 October 2003

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A plasma jet has been developed that operates using rf power and produces a stable homogeneous discharge at atmospheric pressure. Discharge characteristics for the gas mixture of He/O2 and Ar/O2 were studied. The temperature distribution at the exit of the nozzle of Ar/O2 discharge is about 100 K higher than that for the He/O2 discharge—identified by an increased temperature—extends much farther downstream for Ar/O2 discharge in contrast to the He/O2 discharge—250 mm as compared to 75 mm. Optical emission spectra for both discharges in the jet effluent shows only fractions of the peak intensities of Ar, He, and O atomic lines compared with spectra taken looking obliquely inside the jet volume. The spatial profile of excited atomic oxygen at λ=777 nm (4S0 3p–3s) taken side on to the flow direction outside the nozzle shows good correlation to the temperature distribution for both discharges. These results indicate that the Ar/O2 discharge has better energy transfer efficiency than the He/O2 discharge. Study of the electrical properties of the two discharges shows that the two discharges exhibit a different capacitive nature and the voltage wave form for He/O2 advances that of the Ar/O2 discharge by 16°, which means there is more ohmic component in the Ar/O2 discharge. © 2003 American Institute of Physics.
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52.80.-s Electric discharges
52.75.-d Plasma devices
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Activation and diffusion studies of ion-implanted p and n dopants in germanium

Chi On Chui, Kailash Gopalakrishnan, Peter B. Griffin, James D. Plummer, and Krishna C. Saraswat

Appl. Phys. Lett. 83, 3275 (2003); http://dx.doi.org/10.1063/1.1618382 (3 pages) | Cited 91 times

Online Publication Date: 15 October 2003

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We have demonstrated symmetrically high levels of electrical activation of both p- and n-type dopants in germanium. Rapid thermal annealing of various commonly implanted dopant species were performed in the temperature range of 600–850 °C in germanium substrates. Diffusion studies were also carried out by using different anneal times and temperatures. T-SUPREM™ simulations were used to fit the experimental profiles and to extract the diffusion coefficient of various dopants. © 2003 American Institute of Physics.
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61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
66.30.J- Diffusion of impurities
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.S- Impurities in crystals

Crystallization control of sputtered Ta2O5 thin films by substrate bias

A. P. Huang, S. L. Xu, M. K. Zhu, B. Wang, H. Yan, and T. Liu

Appl. Phys. Lett. 83, 3278 (2003); http://dx.doi.org/10.1063/1.1610247 (3 pages) | Cited 13 times

Online Publication Date: 15 October 2003

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This letter reports that, by applying a bias to Si substrates, crystalline tantalum pentoxide (Ta2O5) thin films were fabricated at low substrate temperatures. At 620 °C, it was found that the thin films as-prepared are amorphous without the bias and of high crystallinity with the bias over −100 V. Based on the present data, it is concluded that the crystallinity of the thin films is improved with increasing bias. Furthermore, when the bias was increased to −200 V, partially crystallized films could be attained at temperatures as low as 400 °C. The bias effect on the crystallization is attributed to the interaction of positive ions in the plasma with the growing surface. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
81.15.Cd Deposition by sputtering

Frequency entrainment for micromechanical oscillator

M. Zalalutdinov, K. L. Aubin, M. Pandey, A. T. Zehnder, R. H. Rand, H. G. Craighead, J. M. Parpia, and B. H. Houston

Appl. Phys. Lett. 83, 3281 (2003); http://dx.doi.org/10.1063/1.1618363 (3 pages) | Cited 13 times

Online Publication Date: 15 October 2003

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We demonstrate synchronization of laser-induced self-sustained vibrations of radio-frequency micromechanical resonators by applying a small pilot signal either as an inertial drive at the natural frequency of the resonator or by modulating the stiffness of the oscillator at double the natural frequency. By sweeping the pilot signal frequency, we demonstrate that the entrainment zone is hysteretic and can be as wide as 4% of the natural frequency of the resonator, 400 times the 1/Q ∼ 10−4 half-width of the resonant peak. Possible applications are discussed based on the wide range of frequency tuning and the power gain provided by the large amplitude of self-oscillations (controlled by a small pilot signal). © 2003 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems

Pressure effect on glass transition in a Zr65Al7.5Cu27.5 metallic glass

H. J. Jin, P. Wen, and K. Lu

Appl. Phys. Lett. 83, 3284 (2003); http://dx.doi.org/10.1063/1.1621076 (3 pages) | Cited 4 times

Online Publication Date: 15 October 2003

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By means of the enthalpy recovery experiments in a Zr65Al7.5Cu27.5 metallic glass, the glass transition process was found to correlate with an obvious variation of enthalpy change with the annealing temperature. With this correlation, we developed an approach to determine the pressure effect on the glass transition temperature (Tg), and a drastic increment of Tg up to 50 K was observed in this glass when a hydrostatic pressure of 5 GPa was applied. It is much smaller than that observed in nonmetallic glasses, which is attributed to smaller activation volume of the relaxation in metallic glasses. © 2003 American Institute of Physics.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
62.50.-p High-pressure effects in solids and liquids

Tensile stress in hard metal films

G. C. A. M. Janssen, A. J. Dammers, V. G. M. Sivel, and W. R. Wang

Appl. Phys. Lett. 83, 3287 (2003); http://dx.doi.org/10.1063/1.1619561 (3 pages) | Cited 27 times

Online Publication Date: 15 October 2003

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Thin films on substrates are usually in a stressed state. An important, but trivial, contribution to that stress stems from the difference in thermal expansion coefficient of substrate and film. Much more interesting are the intrinsic stresses, resulting from the growth and/or microstructure of the film. Intrinsic compressive stress was explained by d’Heurle in 1970. Intrinsic tensile stress for recrystallizing metal films was treated succesfully by Doljack and Hoffman in 1972. In the present letter we explain the occurrence of tensile stress in nonrecrystallizing metal films. The explanation is based on modern grain growth models and accurate stress measurements. The key ingredient to the explanation is the proof of the existence of a stress gradient in nonrecrystallizing metal films. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
65.40.De Thermal expansion; thermomechanical effects
68.55.-a Thin film structure and morphology

Optical and structural analysis of ZnCdO layers grown by metalorganic vapor-phase epitaxy

Th. Gruber, C. Kirchner, R. Kling, F. Reuss, A. Waag, F. Bertram, D. Forster, J. Christen, and M. Schreck

Appl. Phys. Lett. 83, 3290 (2003); http://dx.doi.org/10.1063/1.1620674 (3 pages) | Cited 84 times

Online Publication Date: 15 October 2003

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The development of ZnO-based semiconductor devices requires band gap engineering. Ternary Zn1−xCdxO allows reduction of the band gap relative to ZnO, which would be necessary for devices emitting visible light. We have analyzed the structural and optical properties of Zn1−xCdxO layers grown by metalorganic vapor-phase epitaxy. A narrowing of the fundamental band gap of up to 300 meV has been observed, while introducing a lattice mismatch of only 0.5% with respect to binary ZnO. Photoluminescence, high-resolution x-ray diffraction, and spatially resolved cathodoluminescence measurements revealed a lateral distribution of two different cadmium concentrations within the Zn1−xCdxO layers. © 2003 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
81.05.Dz II-VI semiconductors

Low-energy electron-beam irradiation and yellow luminescence in activated Mg-doped GaN

O. Gelhausen, H. N. Klein, M. R. Phillips, and E. M. Goldys

Appl. Phys. Lett. 83, 3293 (2003); http://dx.doi.org/10.1063/1.1619210 (3 pages) | Cited 10 times

Online Publication Date: 15 October 2003

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The effect of low-energy electron-beam irradiation (LEEBI) on native defects and residual impurities in metalorganic-vapor-phase-epitaxy-grown, lightly Mg-doped, p-type GaN was studied by temperature-resolved and excitation power density-resolved cathodoluminescence spectroscopy. Following the LEEBI treatment, the ubiquitous shallow donor–acceptor-pair emission at 3.27 eV decreased, while a deeper DAP emission at ∼3.1 eV dramatically increased in intensity, and a broad yellow luminescence band centered at 2.2 eV evolved. The results clearly indicate that the centers involved in the 3.27 eV transition are not stable during irradiation by low-energy electrons. Further, we report that the LEEBI-treatment not only dissociates neutral Mg-H complexes as intended, but simultaneously dissociates other hydrogenated defect complexes, giving rise to additional radiative recombination channels. © 2003 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors

Temperature-dependent optical studies of Ti1−xCoxO2

S. Guha, K. Ghosh, J. G. Keeth, S. B. Ogale, S. R. Shinde, J. R. Simpson, H. D. Drew, and T. Venkatesan

Appl. Phys. Lett. 83, 3296 (2003); http://dx.doi.org/10.1063/1.1619212 (3 pages) | Cited 9 times

Online Publication Date: 15 October 2003

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We present the results of Raman and photoluminescence studies on epitaxial anatase phase Ti1−xCoxO2 films for x = 0–0.07, grown by pulsed-laser deposition. The low-doped system (x = 0.01 and 0.02) shows a Curie temperature of 700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO2 and shows a small blueshift with increasing doping concentration. The Co-doped samples show two spin-flip emission lines at 2.77 and 2.94 eV. © 2003 American Institute of Physics.
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78.66.Li Other semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
71.35.Aa Frenkel excitons and self-trapped excitons

Origin of nondetectable x-ray diffraction peaks in nanocomposite CuTiZr alloys

J. Z. Jiang, H. Kato, T. Ohsuna, J. Saida, A. Inoue, K. Saksl, H. Franz, and K. Ståhl

Appl. Phys. Lett. 83, 3299 (2003); http://dx.doi.org/10.1063/1.1619220 (3 pages) | Cited 22 times

Online Publication Date: 15 October 2003

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Microscopic structures of Cu60Ti10+xZr30−x (x = 0 and 10) alloys have been investigated by transmission electron microscopy, x-ray diffraction (XRD) and differential scanning calorimeter (DSC). In the Cu60Ti10Zr30 samples annealed at 708 K for times ranging from 0 to 130 min, where the enthalpy of the first exothermic peak decreases by 80%, the corresponding XRD patterns still look similar to that for the as-prepared sample. However, the simulated XRD patterns for the pure Cu51Zr14 phase, which is the crystalline phase formed during the first exothermic reaction, with small grain sizes and defects clearly show a broadened amorphous-like feature. This might be the reason that no diffraction peaks from the nanocrystalline component were detected in the XRD patterns recorded for the as-cast or as-spun Cu60Ti10+xZr30−x (x = 0 and 10) alloys and for the alloys annealed at lower temperatures, in which the enthalpy of the first exothermic peak has a significant reduction. The second exothermic peak found in DSC curves is due to the formation of another hexagonal phase, spacing group P63/mmc (194) and lattice parameters a = 5.105 Å and c = 8.231 Å. © 2003 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
61.05.cp X-ray diffraction
81.40.Gh Other heat and thermomechanical treatments
82.60.Cx Enthalpies of combustion, reaction, and formation

Polyelectrolyte nanolayers as diffusion barriers for Cu metallization

P. G. Ganesan, J. Gamba, A. Ellis, R. S. Kane, and G. Ramanath

Appl. Phys. Lett. 83, 3302 (2003); http://dx.doi.org/10.1063/1.1618951 (3 pages) | Cited 15 times

Online Publication Date: 15 October 2003

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Cu interconnect technology requires the use of <5-nm-thick interfacial layers to inhibit Cu transport into adjacent dielectric layers. We demonstrate the use of 3.5-nm-thick polyelectrolyte layers comprising polyethyleneimine (PEI) and polyacrylic acid (PAA) for this application. Cu/PAA/PEI/SiO2/Si structures show more than a factor-of-5 greater failure time compared to that observed in Cu/SiO2/Si structures. Increasing the number of PAA/PEI bilayers does not show any further improvement in barrier properties. Spectroscopic probing of the Cu/PAA interface reveals that polychelation of Cu with carboxyl groups in PAA is the primary reason for Cu immobilization. Our study suggests that polyelectrolyte nanolayers are attractive for applications such as tailoring barrierless low-k polymeric dielectrics, and for isolating nanoscale components in future device systems. © 2003 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
68.35.Fx Diffusion; interface formation

Melting behavior of levitated Y2O3

L. Hennet, D. Thiaudière, C. Landron, P. Melin, D. L. Price, J.-P. Coutures, J.-F. Bérar, and M.-L. Saboungi

Appl. Phys. Lett. 83, 3305 (2003); http://dx.doi.org/10.1063/1.1621090 (3 pages) | Cited 9 times

Online Publication Date: 15 October 2003

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The yttrium environment in liquid Y2O3 at 2770 K has been measured with anomalous x-ray scattering, aerodynamic levitation, and laser heating. The Y–O coordination of 6–7 and the Y–Y coordination of around 12 imply that the close packing of the high-temperature (H-type) solid phase is preserved on melting, in contrast to the large structural changes exhibited by Al2O3. The unusually sharp main diffraction peak implies a high degree of chemical order and mirrors the diffraction pattern of the H-type phase. © 2003 American Institute of Physics.
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61.25.-f Studies of specific liquid structures
64.70.D- Solid-liquid transitions
78.70.Ck X-ray scattering
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