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23 Feb 1998

Volume 72, Issue 8, pp. 873-995

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Quantum transport in metallic nanowires fabricated by electrochemical deposition/dissolution

C. Z. Li and N. J. Tao

Appl. Phys. Lett. 72, 894 (1998); http://dx.doi.org/10.1063/1.120928 (3 pages) | Cited 69 times

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A nonmechanical method for fabricating a metallic narrow constriction between two electrodes using electrochemical deposition is described. The width of the constriction can be adjusted by slowly dissolving metal atoms away or redepositing atoms onto the constriction which can be controlled flexibly by the electrodes’ potentials. Well-defined plateaus near the integer numbers of the conductance quantum have been observed in these constrictions at room temperature. Since no mechanical movements are involved, this method has the potential of fabricating nanoconstrictions with long term stability. © 1998 American Institute of Physics.
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73.23.-b Electronic transport in mesoscopic systems
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
82.45.-h Electrochemistry and electrophoresis
81.15.Pq Electrodeposition, electroplating

Short-range disorder in lanthanum-doped lead titanate ceramics probed by Raman scattering

E. C. S. Tavares, P. S. Pizani, and J. A. Eiras

Appl. Phys. Lett. 72, 897 (1998); http://dx.doi.org/10.1063/1.120929 (3 pages) | Cited 28 times

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Raman scattering has been used to probe short-range structural information on lanthanum-doped lead titanate ceramics (LaxPb1−xTiO3) for x, ranging from 0.0 to 0.30. In highly doped samples (x>0.27), x-ray diffraction measurements indicate a cubic structure, although measurements of Raman scattering at temperatures above and below the tetragonal to cubic transition showed a residual short-range structural disorder in the cubic phase. Moreover, for these highly lanthanum-doped samples, a well-defined temperature-induced ferro–paraelectric phase transition disappears, which suggests a relationship between local disorder and relaxor behavior in this material. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
78.35.+c Brillouin and Rayleigh scattering; other light scattering
77.80.-e Ferroelectricity and antiferroelectricity

Rotating-compensator multichannel ellipsometry for characterization of the evolution of nonuniformities in diamond thin-film growth

Joungchel Lee, P. I. Rovira, Ilsin An, and R. W. Collins

Appl. Phys. Lett. 72, 900 (1998); http://dx.doi.org/10.1063/1.120930 (3 pages) | Cited 11 times

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A multichannel spectroscopic ellipsometer based on the rotating-compensator principle has been applied to obtain the evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a nanocrystalline diamond film during growth. Spectra in the ellipsometry angles (ψ, Δ) provide the time evolution of the microstructure and optical properties of the film in thin layers, whereas the spectra in the degree of polarization provide the time evolution of nonuniformities in the growth process attributed to light scattering by diamond nuclei in the initial stage of growth and to thickness gradients over the probed area in thicker layers. © 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
78.66.Db Elemental semiconductors and insulators
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.07.-b Nanoscale materials and structures: fabrication and characterization

In situ determination of the surface roughness of diamond films using optical pyrometry

Z. L. Akkerman, Y. Song, Z. Yin, F. W. Smith, and Roy Gat

Appl. Phys. Lett. 72, 903 (1998); http://dx.doi.org/10.1063/1.120931 (3 pages) | Cited 6 times

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The initial growth of diamond films in a microwave plasma reactor has been studied using in situ two-color infrared pyrometry. Analysis of the observed oscillations of the apparent temperature has yielded the substrate temperature and also the instantaneous film growth rate and rms surface roughness σ. Two distinct regimes of growth have been clearly identified: an initial period of rapidly increasing σ before the diamond nuclei coalesce, followed by a slower increase of σ with thickness as the continuous film grows further. The differing initial roughnesses and emissivities of Si and Mo substrates have been shown to have important effects on the growth of diamond. © 1998 American Institute of Physics.  
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors

Secondary ion yield changes on rippled interfaces

Maxim A. Makeev and Albert-László Barabási

Appl. Phys. Lett. 72, 906 (1998); http://dx.doi.org/10.1063/1.120932 (3 pages) | Cited 8 times

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Sputter erosion often leads to the development of surface ripples. Here we investigate the effect of the ripples on the secondary ion yield, by calculating the yield as a function of the microscopic parameters characterizing the ion cascade (such as penetration depth, widths of the deposited energy distribution) and the ripples (ripple amplitude, wavelength). We find that ripples can strongly enhance the yield, with the magnitude of the effect depending on the interplay between the ion and ripple characteristics. Furthermore, we compare our predictions with existing experimental results.© 1998 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.Ct Interface structure and roughness

Microstructure of epitaxial SrRuO3 thin films on (001) SrTiO3

J. C. Jiang, X. Q. Pan, and C. L. Chen

Appl. Phys. Lett. 72, 909 (1998); http://dx.doi.org/10.1063/1.120870 (3 pages) | Cited 34 times

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Metallic oxide films of SrRuO3 deposited on (001) SrTiO3 by pulsed laser deposition have been investigated by transmission electron microscopy (TEM) techniques. These films have a single crystalline structure with an extremely smooth surface. A TEM study of cross-sectional samples shows that the film grew epitaxially on the (001) surface of the SrTiO3 substrate. The films grew along the [110] directions with an in-plane orientation relationship of either SrRuO3[110]//SrTiO3 [100] and SrRuO3[001]//SrTiO3[010], or SrRuO3[110]//SrTiO3[010] and SrRuO3[001]//SrTiO3 [100]. Domains with a rotation of 90° around SrRuO3[110] were observed in the dark-field image of plan-view samples. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Defect induced lowering of activation energies at step bands in Co/Cu(100)

S. T. Coyle, M. R. Scheinfein, and James L. Blue

Appl. Phys. Lett. 72, 912 (1998); http://dx.doi.org/10.1063/1.120871 (3 pages) | Cited 4 times

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Complex topological features such as rectangular voids and step inclusions that were seen in secondary electron micrographs of Co films grown on Cu(100) at room temperature were reproduced in Monte Carlo simulations in the presence of step bands. Lowered activation energies at defects such as steps, kinks, and vacancies enhance step edge restructuring during growth and upon annealing. This results in features such as faceted step edges, rectangular pits, incorporation of Co into terraces, surface alloying, and surface segregation. Simulated growth structures are directly compared with those observed in an ultrahigh vacuum scanning transmission electron microscope. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Ct Interface structure and roughness
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.35.Fx Diffusion; interface formation
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.J- Point defects and defect clusters

Potentiometry and repair of electrically stressed nanowires using atomic force microscopy

M. C. Hersam, A. C. F. Hoole, S. J. O’Shea, and M. E. Welland

Appl. Phys. Lett. 72, 915 (1998); http://dx.doi.org/10.1063/1.120872 (3 pages) | Cited 36 times

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Using an atomic force microscope equipped with a conducting diamond tip, the surface potential on a current carrying gold nanowire was measured with microvolt potential sensitivity and nanometer spatial resolution. Potentiometry images illustrate the stages of failure of nanowires subjected to current stressing. During this failure process, a discontinuity in the potential gradient and an enhanced resistance region were observed at the failure site until a complete fracture was formed. By increasing the repulsive force and accurately positioning the tip, gold could be manipulated into the nanoscale fracture so that the electrical conductivity of the nanowire was regained. © 1998 American Institute of Physics.
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73.23.-b Electronic transport in mesoscopic systems
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.25.+i Surface conductivity and carrier phenomena

Mechanical relaxation and “intramolecular plasticity” in carbon nanotubes

B. I. Yakobson

Appl. Phys. Lett. 72, 918 (1998); http://dx.doi.org/10.1063/1.120873 (3 pages) | Cited 142 times

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The question of how carbon nanotubes (CNT)—believed to be the strongest filaments—relax under tension has been addressed. A dislocation theory applied to a two-dimensional nanocrystal such as the CNT describes the main routes of mechanical relaxation in this molecular structure: a brittle cleavage or, at high temperatures, a plastic flow. Both start with diatomic rotation, which “unlocks” the pristine wall of CNT by creating a dislocation dipole with the pentagon–heptagon cores. Under high stress, the dislocations depart from each other along helical paths, leaving behind a nanotube of smaller diameter, well-defined new symmetry, and changed electrical properties. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.72.Bb Theories and models of crystal defects
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