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29 Mar 1999

Volume 74, Issue 13, pp. 1785-1922

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Elastic constants and their pressure dependence of Zr41Ti14Cu12.5Ni9Be22.5C1 bulk metallic glass

Wei-Hua Wang, R. J. Wang, F. Y. Li, D. Q. Zhao, and M. X. Pan

Appl. Phys. Lett. 74, 1803 (1999); http://dx.doi.org/10.1063/1.123091 (3 pages) | Cited 62 times

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The acoustic velocities and their pressure dependence of bulk Zr41Ti14Cu12.5Ni9Be22.5C1 metallic glass (MG) have been measured up to 0.5 GPa by using a pulse echo overlap method. The elastic constants and thermodynamic parameters as well as their pressure dependence of the MG have been determined. The obtained elastic constants were compared to that of other kinds of glasses. More information about the microstructure, elastic properties, and glass forming ability of the MG was obtained. © 1999 American Institute of Physics.
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62.20.D- Elasticity
62.65.+k Acoustical properties of solids
62.50.-p High-pressure effects in solids and liquids
61.43.Fs Glasses
65.20.-w Thermal properties of liquids
65.40.gd Entropy
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Observation of coherent phonons in silver nanoparticles embedded in BaO thin films

W. Qian, H. Yan, J. J. Wang, Y. H. Zou, L. Lin, and J. L. Wu

Appl. Phys. Lett. 74, 1806 (1999); http://dx.doi.org/10.1063/1.123092 (3 pages) | Cited 8 times

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Three kinds of coherent phonons (0.30, 1.90, and 3.75 THz) have been observed in silver nanoparticles embedded in BaO thin films by means of the femtosecond time-resolved pump-probe technique. The generation of 0.3 THz coherent phonons is attributed to the resonant excitation of localized surface plasmon of silver nanopaticles, and the resonant impulsive stimulated Raman scattering in silver aggregates is responsible for the generation of 1.90 and 3.75 THz coherent phonons. © 1999 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
61.46.-w Structure of nanoscale materials
78.47.-p Spectroscopy of solid state dynamics
78.30.-j Infrared and Raman spectra
78.66.Vs Fine-particle systems

Vertical self-alignment of quantum dots in superlattice

Y. W. Zhang, S. J. Xu, and C.-h. Chiu

Appl. Phys. Lett. 74, 1809 (1999); http://dx.doi.org/10.1063/1.123093 (3 pages) | Cited 20 times

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Self-alignment of quantum dots separated by spacer layers is investigated by using a three-dimensional finite element method. We find that the morphology of the top islands is not just simply a reproduction of the buried islands. It is dependent on the arrangement of the buried islands, the interruption time, and the spacer layer thickness. If the buried islands are uniform and regular, with appropriate choice of their spacing and aspect ratio and with a thin spacer layer, there exists a regime in which the steady-state top islands are always uniform and regular, vertically aligned, and stable against small perturbations. For a thicker spacer layer, due to the change of the strain energy density distribution on top of the spacer layer, the top islands are misaligned with the buried islands. If the buried islands are not uniform and regular, our simulations demonstrate the top islands may self-assemble into more uniform and regular arrangements. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Ultraviolet and blue emission from crystalline SiO2 coated with LiNbO3 and LiTaO3

G. G. Siu, X. L. Wu, Y. Gu, and X. M. Bao

Appl. Phys. Lett. 74, 1812 (1999); http://dx.doi.org/10.1063/1.123094 (3 pages) | Cited 20 times

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Crystalline SiO2 (α quartz) coated with LiNbO3 (LN) or LiTaO3 (LT) films emits two strengthened luminescence bands at 368 and 468 nm compared with those of pure α-SiO2, when excited with 280 nm light of a Xe lamp. These two bands strongly depend on the coating: the LN-coated α-SiO2 has a much stronger photoluminescence (PL) than the LT-coated α-SiO2. On the other hand, the two bands are different from those of α-SiO2 in that their excitation spectra do not have any noticeable band in the range 200–320 nm. They could be understood based on excitons in the α-SiO2 surface, which are induced by the photorefractive effect of the coated films. The 368 nm PL band is attributed to the optical transitions of the E′ defect pairs and the 468 nm PL band to the radiative recombination of the self-trapped excitons. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
71.35.Gg Exciton-mediated interactions
78.20.-e Optical properties of bulk materials and thin films

Charge trap dynamics in a SiO2 layer on Si by scanning capacitance microscopy

C. J. Kang, G. H. Buh, S. Lee, C. K. Kim, K. M. Mang, C. Im, and Y. Kuk

Appl. Phys. Lett. 74, 1815 (1999); http://dx.doi.org/10.1063/1.123095 (3 pages) | Cited 30 times

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Trapped electrons and holes, and their dynamics, were visualized from spatially resolved capacitance–voltage (C–V) curves and dC/dV images using scanning capacitance microscopy. A trapped charge of 10−16–10−18 C, localized within 2 μm diam circular test structures, was imaged. The detrapping process of the trapped electrons can be explained with a quantum-mechanical tunneling model. © 1999 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.20.At Surface states, band structure, electron density of states

The intrinsic temperature effect of the Raman spectra of graphite

PingHeng Tan, YuanMing Deng, Qian Zhao, and WenChao Cheng

Appl. Phys. Lett. 74, 1818 (1999); http://dx.doi.org/10.1063/1.123096 (3 pages) | Cited 50 times

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The Raman spectra of ion-implanted highly oriented pyrolytic graphite (HOPG) are reported, in which an additional mode at 1083 cm−1 and three doublet structures in the positions of ∼ 1350, ∼ 2450, and ∼ 2710 cm−1 are revealed. Noticeable frequency shifts are observed for all the Raman bands between the spectra excited with different laser powers, which are interpreted as the pure temperature effect and a downshift in the C–C stretching frequency induced by the thermal expansion. Moreover, the pure temperature effect (dω/dT)V without anharmonic contribution is achieved in pristine HOPG. The results suggest that the pure temperature effect without anharmonic contribution plays an important role in the frequency shifts with temperature. © 1999 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects
63.20.Ry Anharmonic lattice modes
78.30.Hv Other nonmetallic inorganics

Anisotropic photoluminescence in incomplete three-dimensional photonic band-gap environments

S. G. Romanov, A. V. Fokin, and R. M. De La Rue

Appl. Phys. Lett. 74, 1821 (1999); http://dx.doi.org/10.1063/1.123097 (3 pages) | Cited 45 times

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The effect of an incomplete three-dimensional photonic band-gap structure upon the wideband photoluminescence from bare opal and opal impregnated with ZnS has been studied by means of angular-resolved photoluminescence. It has been shown that the photoluminescence becomes anisotropic in accordance with the angular dispersion of the stop band. Suppression of the spontaneous emission in the stop-band energy region and amplification of the spontaneous emission at the edge of the stop band have both been demonstrated. © 1999 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
78.45.+h Stimulated emission

Microstructural study of optically degraded ZnCdSe quantum wells

S. Tomiya, H. Noguchi, Y. Sanaka, T. Hino, S. Taniguchi, and A. Ishibashi

Appl. Phys. Lett. 74, 1824 (1999); http://dx.doi.org/10.1063/1.123098 (3 pages) | Cited 3 times

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The defect structure of optically degraded ZnCdSe quantum wells was investigated using transmission electron microscopy. The defects were composed of the dislocation dipoles with a Burgers vector of b = −(a/2)[101] inclined at 45° to the (001) plane. The dislocation dipoles consist of two segments aligned along the [1math0] direction and the [120] direction. The [1math0] dipole segments lying in the (11math) plane were developed by the recombination-enhanced dislocation glide process, while the [mathmath0] dipole segments lying in the (math11) plane were developed by the recombination-enhanced dislocation climb process. Both processes operate simultaneously. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Dz II-VI semiconductors

Effects of high magnetic field on the morphology of carbon nanotubes and selective synthesis of fullerenes

Haruo Yokomichi, Hiroyuki Sakima, Masaki Ichihara, Fumiko Sakai, Kikuo Itoh, and Naoki Kishimoto

Appl. Phys. Lett. 74, 1827 (1999); http://dx.doi.org/10.1063/1.123099 (3 pages) | Cited 6 times

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Carbon nanotubes and fullerenes were synthesized by arc discharge in a He gas atmosphere under a high magnetic field up to 10 T. Morphology and the yield of these nanotubes were investigated by scanning electron microscopy and transmission electron microscopy (TEM). The yield and type of fullerenes were also evaluated by ultraviolet visual spectroscopy. TEM images revealed that thin collapsed nanotubes having larger curvature were synthesized under a high magnetic field, in particular at 10 T. Furthermore, the ratio of C70 to C60 concentration was found to vary depending on the magnitude of the magnetic field during arc discharge. Based on these results, the effects of magnetic field on the synthesis of carbon nanotubes and fullerenes are discussed. © 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
78.40.Ri Fullerenes and related materials
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