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22 Jun 1998

Volume 72, Issue 25, pp. 3243-3383

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Large-scale and low-cost synthesis of single-walled carbon nanotubes by the catalytic pyrolysis of hydrocarbons

H. M. Cheng, F. Li, G. Su, H. Y. Pan, L. L. He, X. Sun, and M. S. Dresselhaus

Appl. Phys. Lett. 72, 3282 (1998); http://dx.doi.org/10.1063/1.121624 (3 pages) | Cited 214 times

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Rope-like bundles of single-walled carbon nanotubes (SWNTs) similar to those obtained by laser vaporization and electric-arc techniques were synthesized on a relatively large scale and at low cost by the catalytic decomposition of hydrocarbons at a temperature of about 1200 °C using an improved floating catalyst method. The SWNTs thus obtained have larger diameters and are self-organized into ropes. The addition of thiophene was found to be effective in promoting the growth of SWNTs and in increasing the yield of either SWNTs or multiwalled carbon nanotubes under different growth conditions. © 1998 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

Pyroelectric properties of (Pb1−xLax)TiO3 thin films deposited using SrRuO3 as a buffer layer

Yung-Kuan Tseng, Kuo-Shung Liu, Jian-Der Jiang, and I-Nan Lin

Appl. Phys. Lett. 72, 3285 (1998); http://dx.doi.org/10.1063/1.121625 (3 pages) | Cited 26 times

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In this study, we observed that the ferroelectric properties of (Pb1−xLax)TiO3, (PLT) thin films deposited on Pt/Ti/Si substrates using SrRuO3 as a buffer layer change markedly with the substrate temperature and the composition. All the films are perovskite with no secondary phases when deposited at 500–600 °C. However, only the films deposited below 520 °C possess a satisfactory small leakage current density, for example, JL ⩽ 10−7 A/cm2, under a 50 kV/cm applied field. Both PLT10 (x = 0.10) and PLT5 (x = 0.05) thin films thus obtained possess large pyroelectric coefficient (p = 0.009–0.018 °C−1). However, the PLT10 thin films show pyroelectric properties markedly superior to the PLT5 thin films, although the PLT5 thin films own much better ferroelectric properties. This phenomenon is explained by the lower Curie temperature (Tc) of the PLT10 materials. © 1998 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
77.70.+a Pyroelectric and electrocaloric effects
77.80.B- Phase transitions and Curie point

Film thickness and composition monitoring during growth by molecular beam epitaxy using alpha particle energy loss

M. Beaudoin, M. Adamcyk, Z. Gelbart, U. Giesen, I. Kelson, Y. Levy, J. A. MacKenzie, and T. Tiedje

Appl. Phys. Lett. 72, 3288 (1998); http://dx.doi.org/10.1063/1.121626 (3 pages) | Cited 2 times

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The α-particle energy loss method (AEL) has been implemented in situ to monitor film thickness during growth by molecular beam epitaxy. For InP and GaAs substrates recoil implanted with α-particle emitters, we have been able to measure thickness and composition of deposited GaAs, AlGaAs and InGaAs in real time. The AEL method yields in situ real time results comparable in accuracy to those obtained by ex situ scanning electron microscope and high-resolution x-ray diffraction measurements. © 1998 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.80.Jh Ion radiation effects

Metal–oxide bilayer Raman scattering in SrTiO3 thin films

Vladimir I. Merkulov, Jon R. Fox, Hong-Cheng Li, Weidong Si, A. A. Sirenko, and X. X. Xi

Appl. Phys. Lett. 72, 3291 (1998); http://dx.doi.org/10.1063/1.121627 (3 pages) | Cited 18 times

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We have used a metal–oxide bilayer Raman scattering technique to study lattice dynamics in SrTiO3 thin films. The SrTiO3 thin films were epitaxially grown on a conducting metal–oxide layer which reflects the exciting laser beam so that it does not enter the LaAlO3 substrate. Raman scattering from the SrTiO3 thin films was clearly observed, including the first-order Raman peaks forbidden by the cubic symmetry in single crystals. We suggest that strain exists in the films, which changes the crystal symmetry and will affect the dielectric properties of the SrTiO3 thin films. © 1998 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
78.30.Hv Other nonmetallic inorganics
77.80.-e Ferroelectricity and antiferroelectricity
78.66.Nk Insulators
63.20.-e Phonons in crystal lattices

Crystallization and orientation of C60 from C60/polymethyl methacrylate films

Guanghua Chen and Guobin Ma

Appl. Phys. Lett. 72, 3294 (1998); http://dx.doi.org/10.1063/1.121628 (3 pages) | Cited 1 time

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The crystallization and orientation behaviors of C60 for C60-doped polymethyl methacrylate films are reported. The results show a high tendency of crystallization of C60 with increasing its content, and a preferential (111) orientation for heavily doped films upon high-temperature annealing. The expansion of the lattice constant and the existence of hexagonal close-packed stacking faults are also investigated. The orientation phenomenon indicates an efficient method for the growth of (111)-oriented C60 on a variety of substrates, including those with strong surface bondings on which the orientation is difficult to form via conventional methods.© 1998 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology
61.72.Nn Stacking faults and other planar or extended defects

Growth of carbon nanotubes on cobalt disilicide precipitates by chemical vapor deposition

J. M. Mao, L. F. Sun, L. X. Qian, Z. W. Pan, B. H. Chang, W. Y. Zhou, G. Wang, and S. S. Xie

Appl. Phys. Lett. 72, 3297 (1998); http://dx.doi.org/10.1063/1.121629 (3 pages) | Cited 20 times

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We have successfully grown carbon nanotubes on cobalt-implanted silicon with various doses. The morphology of such tubes has been examined by scanning electron microscopy, transmission electron microscopy, and Raman scattering. On contrary to the commonly used transition-metal nanoparticle catalysts, nanometer-sized CoSi2 precipitates produced in the as-implanted substrates are believed to act as nucleation centers for the formation of carbon nanotubes. © 1998 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.30.Hv Other nonmetallic inorganics
78.66.Jg Amorphous semiconductors; glasses

Dynamics of polarization loss in (Pb,La)(Zr,Ti)O3 thin film capacitors

I. G. Jenkins, T. K. Song, S. Madhukar, A. S. Prakash, S. Aggarwal, and R. Ramesh

Appl. Phys. Lett. 72, 3300 (1998); http://dx.doi.org/10.1063/1.121630 (3 pages) | Cited 26 times

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We report results of high-speed polarization relaxation measurements in ferroelectric thin film capacitors. Polarization relaxation has been reported to occur in two distinct time regimes, one for relaxation times in the range of a few milliseconds and a second for longer relaxation times. We find that the polarization relaxation in the first regime is governed by at least two different physical processes, namely depoling fields and the activation field for switching. Using prototypical epitaxial PbZr0.2Ti0.8O3 and Pb0.9La0.1Zr0.2Ti0.8O3 test capacitors, we demonstrate the effect of film microstructure and switching speed on the relaxation dynamics in the first regime. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.80.Fm Switching phenomena
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
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