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20 Apr 1998

Volume 72, Issue 16, pp. 1939-2058

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Synthesis of boron nitride nanotubes by means of excimer laser ablation at high temperature

D. P. Yu, X. S. Sun, C. S. Lee, I. Bello, S. T. Lee, H. D. Gu, K. M. Leung, G. W. Zhou, Z. F. Dong, and Z. Zhang

Appl. Phys. Lett. 72, 1966 (1998); http://dx.doi.org/10.1063/1.121236 (3 pages) | Cited 95 times

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Boron nitride nanotubes (BN-NTs) were synthesized by using excimer laser ablation at 1200 °C in different carrier gases. The main characteristic of the BN-NTs produced by this method is that nanotubes are of only one to three atomic layers thick, which could be attributed to the dominance of the axial growth rate over the radial growth rate. The diameter of the BN-NTs ranged from 1.5 to 8 nm. The tips of the BN-NTs are either a flat cap or of polygonal termination, in contrast to the conical ends of carbon nanotubes. The atomic ratio of boron to nitrogen as measured by means of parallel electron energy loss spectroscopy is 0.8, which is within the experimental error of the stoichiometry of hexagonal BN structure. © 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
79.20.Kz Other electron-impact emission phenomena
61.66.Bi Elemental solids
61.66.Dk Alloys

Multimillion-atom molecular dynamics simulation of atomic level stresses in Si(111)/Si3N4(0001) nanopixels

Martina E. Bachlechner, Andrey Omeltchenko, Aiichiro Nakano, Rajiv K. Kalia, Priya Vashishta, Ingvar Ebbsjö, Anupam Madhukar, and Paul Messina

Appl. Phys. Lett. 72, 1969 (1998); http://dx.doi.org/10.1063/1.121237 (3 pages) | Cited 26 times

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Ten million atom multiresolution molecular-dynamics simulations are performed on parallel computers to determine atomic-level stress distributions in a 54 nm nanopixel on a 0.1 μm silicon substrate. Effects of surfaces, edges, and lattice mismatch at the Si(111)/Si3N4(0001) interface on the stress distributions are investigated. Stresses are found to be highly inhomogeneous in the nanopixel. The top surface of silicon nitride has a compressive stress of +3 GPa and the stress is tensile, −1 GPa, in silicon below the interface. © 1998 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
81.05.Cy Elemental semiconductors
68.60.Bs Mechanical and acoustical properties
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

The effect of composition on the thermal stability of Si1−x−yGexCy/Si heterostructures

L. V. Kulik, D. A. Hits, M. W. Dashiell, and J. Kolodzey

Appl. Phys. Lett. 72, 1972 (1998); http://dx.doi.org/10.1063/1.121238 (3 pages) | Cited 15 times

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The thermal stability of molecular beam epitaxy grown Si1−x−yGexCy/Si heterostructures (0 ⩽ x<0.30, y ∼ 0.008) was studied using infrared absorption spectroscopy. The local vibrational mode of C in Si and Si1−x−yGex was used to quantify the loss of C atoms from substitutional sites with high temperature annealing. The activation energy (Ea = 4.9 eV) for the loss of substitutional C achieved a maximum for the strain compensated alloy (x ∼ 0.1). An additional increase of Ge content resulted in a rapid decrease in Ea, which was found to be 3.4 eV for x ∼ 0.27. The nonmonotonic behavior of Ea on Ge content is explained by the effect of the interface strain between the epitaxial layer and Si substrate. © 1998 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.Am Elemental semiconductors and insulators
78.30.Hv Other nonmetallic inorganics
61.72.Cc Kinetics of defect formation and annealing
63.20.Pw Localized modes
78.66.Li Other semiconductors
78.66.Db Elemental semiconductors and insulators

Optical unwinding and reentrance phenomena in chiral smectic-C liquid crystals

Shu-Hsia Chen and Ching-Yih Chen

Appl. Phys. Lett. 72, 1975 (1998); http://dx.doi.org/10.1063/1.121264 (3 pages)

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We optically measure the molecular reorientation induced by an argon laser in homeotropically aligned chiral smectic-C films. Optical unwinding of the helix is observed and the critical unwinding intensity is determined. We have also developed a theory which not only explains the observed effect but also predicts a novel reentrance phenomenon of the unwinding state. © 1998 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
68.15.+e Liquid thin films
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.80.-e Ferroelectricity and antiferroelectricity
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Reflective mode of a nematic liquid crystal with chirality in a hybrid aligned configuration

Young Jin Kim and Sin-Doo Lee

Appl. Phys. Lett. 72, 1978 (1998); http://dx.doi.org/10.1063/1.121239 (3 pages) | Cited 5 times

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A reflective type of a liquid crystal (LC) display is proposed in a twisted hybrid aligned configuration with a reflective electrode and a single polarizer. A chiral dopant was introduced into a nematic LC to produce a proper amount of twist in a hybrid aligned geometry. Numerical simulations were performed to optimize the cell parameters so that the electro-optical switching between the black and white states could be easily achieved. It was experimentally demonstrated that this reflective mode gives wide viewing and fast response characteristics. The effect of an optical retardation film on the device performance is also discussed. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
78.20.Jq Electro-optical effects
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

The role of nonstoichiometry in 180° domain switching of LiNbO3 crystals

Venkatraman Gopalan, Terence E. Mitchell, Y. Furukawa, and K. Kitamura

Appl. Phys. Lett. 72, 1981 (1998); http://dx.doi.org/10.1063/1.121491 (3 pages) | Cited 114 times

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We show here conclusively that the internal field originates from nonstoichiometric point defects in LiNbO3 crystals. The switching fields required for 180° domain reversal in congruent crystals [C=Li2O/(Li2O+Nb2O5) = 0.484] are ∼4–5 times larger than the switching fields for nearstoichiometric crystals (C = 0.498). An internal field of ∼2.5 kV/mm observed in congruent crystals disappears in stoichiometric crystals. The concentration of hydrogen incorporated during crystal growth has no effect on the switching or internal fields. The measured spontaneous polarization, Ps = 80±5 μC/cm2 is relatively insensitive to the crystal nonstoichiometry and the hydrogen content. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
61.72.J- Point defects and defect clusters
61.66.Bi Elemental solids
61.66.Dk Alloys
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