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15 Nov 1999

Volume 75, Issue 20, pp. 3051-3226

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Formation of single-wall carbon nanotubes by laser ablation of fullerenes at low temperature

Y. Zhang and S. Iijima

Appl. Phys. Lett. 75, 3087 (1999); http://dx.doi.org/10.1063/1.125239 (3 pages) | Cited 31 times

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Laser ablation products from fullerene materials have been studied by transmission electron microscopy and Raman spectroscopy. Using nickel and cobalt as a catalyst, single-wall carbon nanotubes were produced at an ambient temperature of 400 °C. The results were compared with those using graphite as starting materials. It is suggested that the formation of single-wall carbon nanotubes is controlled by both the availability of proper precursors and the activity of the metal catalyst. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
79.20.Ds Laser-beam impact phenomena
81.20.-n Methods of materials synthesis and materials processing

Microstructure imaging of C54–TiSi2 polycrystalline thin films by micro-Raman spectroscopy

F. Meinardi, S. Quilici, A. Borghesi, and G. Artioli

Appl. Phys. Lett. 75, 3090 (1999); http://dx.doi.org/10.1063/1.125240 (3 pages) | Cited 8 times

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The morphology of C54–TiSi2 polycrystalline films has been revealed by the micro-Raman imaging technique. This was based on the calculation of the symmetries of the Raman active vibrations of the C54–TiSi2 single crystal and subsequent polarized Raman measurements to detect and unambiguously label all the expected peaks. The relative intensity of two suitable peaks was monitored and mapped on C54–TiSi2 blanket films. Grains with different orientation are clearly detectable, and the microstructure properties of the film can be analyzed. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Hydrogen in the mechanically prepared nanostructured graphite

S. Orimo, G. Majer, T. Fukunaga, A. Züttel, L. Schlapbach, and H. Fujii

Appl. Phys. Lett. 75, 3093 (1999); http://dx.doi.org/10.1063/1.125241 (3 pages) | Cited 82 times

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Nanostructured graphite was prepared by mechanical milling under hydrogen atmosphere. Several samples obtained after different milling times were systematically examined to get fundamental information about the structures and hydrogen concentrations. After the expansion of the graphite interlayer, the long-range ordering of the interlayer disappears continuously with increasing milling time. The hydrogen concentration reaches up to 7.4 mass % (CH0.95) after milling for 80 h. Judging from the radial distribution function determined by the neutron diffraction measurement, there are two types of deuterium coordinations: deuterium atoms in the graphite interlayers and that with the CDx covalent bonds, respectively. © 1999 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Generation and detection of fluorescent color centers in diamond with submicron resolution

J. Martin, R. Wannemacher, J. Teichert, L. Bischoff, and B. Köhler

Appl. Phys. Lett. 75, 3096 (1999); http://dx.doi.org/10.1063/1.125242 (3 pages) | Cited 30 times

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Fluorescent color-center patterns have been written on surfaces of synthetic type-Ib diamonds with spatial resolution below 180 nm via irradiation with focused ion and electron beams and subsequent annealing. The patterns are detected and spectroscopically analyzed using confocal optical microscopy. From the spatial extent of the color-center distributions, the activation energy for diffusion of vacancies in diamond is determined as (2.55±0.15) eV. Detailed information about the formation of color centers in diamond is obtained employing the three-dimensional spatial resolution of the confocal microscope combined with spectral resolution. In particular, the distributions of two color centers, ascribed to different charge states of the NV defect in diamond, have been spatially mapped and shown to depend strongly on the irradiation dose. © 1999 American Institute of Physics.
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61.72.J- Point defects and defect clusters
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
81.40.Gh Other heat and thermomechanical treatments
78.55.Ap Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
66.30.H- Self-diffusion and ionic conduction in nonmetals

Observation of large-scale surface undulations due to inhomogeneous dislocation strain fields in lattice-mismatched epitaxial layers

G. Springholz

Appl. Phys. Lett. 75, 3099 (1999); http://dx.doi.org/10.1063/1.125243 (3 pages) | Cited 7 times

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The surface structure of highly relaxed IV–VI heteroepitaxial layers is studied using scanning tunneling and scanning force microscopy. For bilayer structures consisting of highly relaxed EuTe layers covered by thick PbTe buffer layers, huge surface undulations with amplitudes as large as 50 Å are observed. These undulations are completely decoupled from the epitaxial surface step structure and can be observed even for rather large cap layer thicknesses. The deconvolution of the surface profiles shows that the surface undulations are purely caused by the nonuniform misfit dislocation network at the EuTe/PbTe interface. On the contrary, no indication is found that these dislocation strain fields give rise to surface structures formed by preferential growth. © 1999 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
68.55.-a Thin film structure and morphology

Dynamics of ultrafast reversible phase transitions in GeSb films triggered by picosecond laser pulses

J. Siegel, C. N. Afonso, and J. Solis

Appl. Phys. Lett. 75, 3102 (1999); http://dx.doi.org/10.1063/1.125244 (3 pages) | Cited 26 times

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The dynamics and the reversibility conditions of crystalline↔amorphous transitions induced in thin Ge0.07Sb0.93 films upon picosecond laser pulse melting were studied by real-time reflectivity measurements with nanosecond and picosecond resolution. The full transformation time could be resolved in a single exposure experiment using a novel setup based on a streak camera. It is shown that under optimum conditions both crystallization and amorphization are completed within 400 ps. The fundamental requirement for the occurrence of such ultrafast phase transformations is to reduce the latent heat released upon solidification. Amorphization is then achieved via bulk solidification of the fully molten film at a very large supercooling. © 1999 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.47.-p Spectroscopy of solid state dynamics
64.70.K- Solid-solid transitions
78.66.Jg Amorphous semiconductors; glasses
61.43.Fs Glasses

Polymerized carbon nanobells and their field-emission properties

Xucun Ma, Enge Wang, Wuzong Zhou, David A. Jefferson, Jun Chen, Shaozhi Deng, Ningsheng Xu, and Jun Yuan

Appl. Phys. Lett. 75, 3105 (1999); http://dx.doi.org/10.1063/1.125245 (3 pages) | Cited 101 times

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Aligned nitrogen-containing carbon nanofibers consisting of polymerized “nanobells” have been grown on a large scale using microwave plasma-assisted chemical-vapor deposition with a mixture of methane and nitrogen. A greater part of the fiber surface consists of open ends of the graphitic sheets. A side-emission mechanism is proposed. A low-threshold field of 1.0 V/μm and a high-emission current density of 200 mA/cm2 for an applied field of 5–6 V/μm were achieved, implying that the materials have a high potential for future application as electron field emitters, especially in flat-panel displays. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
73.61.Wp Fullerenes and related materials
81.05.ub Fullerenes and related materials
79.70.+q Field emission, ionization, evaporation, and desorption

Electron-stimulated conversion of chemisorbed O to Al2O3 on Al(111)

I. Popova, V. Zhukov, and J. T. Yates

Appl. Phys. Lett. 75, 3108 (1999); http://dx.doi.org/10.1063/1.125246 (3 pages) | Cited 10 times

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The transformation of a chemisorbed O layer on the Al(111) surface into Al2O3 under electron impact has been monitored by high-resolution electron energy-loss and x-ray photoelectron spectroscopies. Electron irradiation (100 eV) of chemisorbed O was observed to cause spectroscopic changes in the surface layer indicative of oxide formation. The energy transfer from the electrons to the chemisorbed O atoms through electronic excitations, leading to vibrationally excited adsorbed particles, is proposed to be responsible for the observed conversion of chemisorbed oxygen to Al2O3. The cross section for this electron-induced process is estimated to be 2×10−19 cm2 for 100 eV electrons. © 1999 American Institute of Physics.
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81.65.Mq Oxidation
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
61.80.Fe Electron and positron radiation effects
61.82.Bg Metals and alloys
79.20.Kz Other electron-impact emission phenomena
79.60.Dp Adsorbed layers and thin films

Mechanochemical reaction and formation of an amorphous nitride phase during ball milling of Si in NH3

Z. L. Li, J. S. Williams, D. J. Llewellyn, and M. Giersig

Appl. Phys. Lett. 75, 3111 (1999); http://dx.doi.org/10.1063/1.125247 (3 pages) | Cited 2 times

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The formation of an amorphous SixNyH phase is obtained by a solid–gas mechanochemical reaction induced by ball milling of Si in NH3 gas. We suggest that mechanical damage together with absorbed N and H play an important role in the formation and stability of the amorphous SixNyH phase during milling. Transmission electron microscopy, x-ray diffraction, thermal analysis, and composition analysis have been used to characterize the samples after ball milling and subsequent annealing. Crystallization of the amorphous phase to α-Si3N4 is observed at temperatures above 800 °C. © 1999 American Institute of Physics.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.43.Er Other amorphous solids

Optical switching property of a light-induced pinhole in antimony thin film

Toshio Fukaya, Junji Tominaga, Takashi Nakano, and Nobufumi Atoda

Appl. Phys. Lett. 75, 3114 (1999); http://dx.doi.org/10.1063/1.125248 (3 pages) | Cited 31 times

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Optical near-field recording, called a super-resolution near-field structure, records and retrieves small marks beyond the diffraction limit. A thin layer of an antimony (Sb) film, added to the usual phase-change optical disk, is the key material of this technique. Nonlinear optical properties of an Sb film, especially optical switching, were studied in the stationary state using a nanosecond pulse laser. Clear switching was observed under microscopic measurement. © 1999 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Vb Optical storage systems, optical disks
42.79.Wc Optical coatings

Influence of Si doping on the infrared reflectance characteristics of GaN grown on sapphire

Y. T. Hou, Z. C. Feng, S. J. Chua, M. F. Li, N. Akutsu, and K. Matsumoto

Appl. Phys. Lett. 75, 3117 (1999); http://dx.doi.org/10.1063/1.125249 (3 pages) | Cited 7 times

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Si-doped GaN films grown on sapphire are investigated by infrared reflectance. A damping behavior of the interference fringes is observed, and interpreted to be due to the presence of an interface layer between the film and the substrate. A theoretical calculation using a two-layer model to take into account the interface layer resulted in this damping in agreement with the experiment. The damping behavior and an improvement of interface properties by Si incorporation are demonstrated. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Optical properties of CdSe nanocrystals in a polymer matrix

Andrea V. Firth, D. J. Cole-Hamilton, and J. W. Allen

Appl. Phys. Lett. 75, 3120 (1999); http://dx.doi.org/10.1063/1.125250 (3 pages) | Cited 20 times

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Cadmium selenide nanocrystals have been made in a transparent polymer matrix by synthesis at room temperature. Particle size is controlled by reaction time or reagent concentration. Larger nanocrystals (≳3 nm) show near-band-edge photoluminescence. Smaller ones have a broad emission extending across the visible region. Atmospheric moisture causes the emission intensity to decrease but subsequent exposure to light reverses this and gives a material which is no longer quenched by moisture. The broad emission and stability against atmospheric moisture leads to possible device applications of a “white” phosphor. © 1999 American Institute of Physics.
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78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Limits of residual stress in Cr films sputter deposited on biased substrates

A. Misra and M. Nastasi

Appl. Phys. Lett. 75, 3123 (1999); http://dx.doi.org/10.1063/1.125251 (3 pages) | Cited 12 times

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Stress evolution in thin Cr films on Si substrates is studied as a function of substrate bias. With increasing bias voltage, the tensile stress is observed to increase to a maximum, transition to compressive stress that also reaches a maximum. We relate the tensile stress maximum to the maximum in attractive interatomic forces between the coalescing islands, and the compressive stress maximum to the saturation in Frenkel defect concentration, with smaller contribution from entrapped Ar. We show that the maxima in both tensile and compressive residual stress correspond to the film yield strength. Compressive yield strength is higher as compared to tensile due to hardening from point defects. © 1999 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Strain-imaging observation of the polarization freezing of the domains under the electrode of a Pb(Zr, Ti)O3 film

K. Takata, H. Miki, K. Torii, K. Kushida-Abdelghafar, and Y. Fujisaki

Appl. Phys. Lett. 75, 3126 (1999); http://dx.doi.org/10.1063/1.125252 (3 pages) | Cited 5 times

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Strain imaging is used to measure and image piezoelectric properties by detecting electric-field-induced strains using a scanning probe microscope. In this letter, we present ferroelectric domain imaging under an electrode in a lead-zirconate-titanate (PZT) film. The imaging has been achieved by detecting the surface force modulation caused by the electrode displacements. Observation through the electrode suppresses the effect of space charges and enables us to investigate the PZT film in the same situation in devices. We observed the freezing of polarization of a PZT film deoxidized by atomic hydrogen produced by catalysis of platinum upper electrodes due to hydrogen annealing. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
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