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13 Mar 2000

Volume 76, Issue 11, pp. 1353-1479

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Structures and optical properties of silicon nanocrystallites prepared by pulsed-laser ablation in inert background gas

Nobuyasu Suzuki, Toshiharu Makino, Yuka Yamada, Takehito Yoshida, and Seinosuke Onari

Appl. Phys. Lett. 76, 1389 (2000); http://dx.doi.org/10.1063/1.126041 (3 pages) | Cited 19 times

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Silicon (Si) nanocrystallites have been synthesized using pulsed-laser ablation in inert background gases, for studying the structures and optical properties as one of the quantum confinement effects. We extracted a process condition where well-dispersed Si nanocrystallites devoid of droplets and debris are prepared, by varying excitation laser conditions. Furthermore, we investigate the influence of the inert background gas pressures on transition from amorphous-like thin films to nanocrystallites. It was clarified that there is a processing window of the inert background gas pressure in which the quantum confinement effects for carriers and phonons become apparent. © 2000 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
81.15.Fg Pulsed laser ablation deposition
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.40.Fy Semiconductors

Scanning tunneling microscopy study of Si(111) surface morphology after removal of SiO2 by synchrotron radiation illumination

Y. Gao, H. Mekaru, T. Miyamae, and T. Urisu

Appl. Phys. Lett. 76, 1392 (2000); http://dx.doi.org/10.1063/1.126042 (3 pages) | Cited 7 times

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The surface morphology of Si(111) was investigated using scanning tunneling microscopy after desorption of surface SiO2 by synchrotron radiation (SR) illumination. The surface shows large regions of atomically flat Si(111)-7×7 structure, and is characterized by the formation of single bilayer steps nicely registered to the underlying crystal structure. This is in sharp contrast to Si(111) surfaces after thermal desorption of SiO2 at temperatures 880 °C and above, where the surface steps are much more irregular. The registration of the surface steps to the underlying crystal structure indicates that the Si(111) surface reaches thermodynamic equilibrium under SR irradiation at temperatures much lower than that necessary for thermal desorption. © 2000 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Indium nanowires in thick (InGaN) layers as determined by x-ray analysis

A. Krost, J. Bläsing, H. Protzmann, M. Lünenbürger, and M. Heuken

Appl. Phys. Lett. 76, 1395 (2000); http://dx.doi.org/10.1063/1.126043 (3 pages) | Cited 10 times

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300-nm-thick InGaN layers with In concentrations up to 21% were grown by low-pressure metalorganic chemical-vapor deposition. Besides the InGaN and GaN Bragg peaks, the symmetric (0002) x-ray spectra of strain-relaxed samples show an additional signal which could be identified stemming from metallic tetragonal indium. The indium is incorporated in InGaN with its pseudohexagonal (101) plane parallel to the InGaN(0001) plane in a sixfold configuration. From the widths and intensities of the asymmetric In(211) and the symmetric In(h0h) diffraction peaks, the lateral and perpendicular crystallite sizes of the In inclusions are estimated to be ∼30 and ∼300 nm, respectively, i.e., the In is incorporated in a wire-like manner in the growth direction. In InGaN-based devices such indium wires could act as highly conducting channels detrimental for electronic and optoelectronic applications. © 2000 American Institute of Physics.
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68.55.Nq Composition and phase identification
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.05.Ea III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization

Saturation of THz-radiation power from femtosecond-laser-irradiated InAs in a high magnetic field

Hideyuki Ohtake, Shingo Ono, Masahiro Sakai, Zhenlin Liu, Takeyo Tsukamoto, and Nobuhiko Sarukura

Appl. Phys. Lett. 76, 1398 (2000); http://dx.doi.org/10.1063/1.126044 (3 pages) | Cited 18 times

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THz-radiation power from femtosecond-pulse-irradiated InAs is found to be saturated at the magnetic field around 3 T. Additionally, we find that this saturation magnetic field strongly depends on geometrical layout. Interesting magnetic-field dependence of the center frequency for THz radiation is also observed. © 2000 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
78.70.Gq Microwave and radio-frequency interactions
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Ey III-V and II-VI semiconductors
84.40.-x Radiowave and microwave (including millimeter wave) technology

Formation dynamics of silicon nanoparticles after laser ablation studied using plasma emission caused by second-laser decomposition

Tetsuya Makimura, Taiji Mizuta, and Kouichi Murakami

Appl. Phys. Lett. 76, 1401 (2000); http://dx.doi.org/10.1063/1.126045 (3 pages) | Cited 17 times

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We have investigated the dynamic formation of silicon nanoparticles after pulsed-laser ablation of a silicon target into argon gas, in order to fabricate the nanoparticles that exhibit visible photoluminescence with higher efficiency. The nanoparticles growing in argon gas were detected by measuring plasma emission resulting from decomposition of the nanoparticles by a second pulsed-laser beam. It was directly observed that the nanoparticles grow on the time scale of 1 ms. © 2000 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
61.46.-w Structure of nanoscale materials
81.15.Fg Pulsed laser ablation deposition

Mechanism of diffusional transport during ion nitriding of aluminum

T. Telbizova, S. Parascandola, U. Kreissig, R. Günzel, and W. Möller

Appl. Phys. Lett. 76, 1404 (2000); http://dx.doi.org/10.1063/1.126070 (3 pages) | Cited 14 times

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The mechanism of diffusional transport during low-energy ion nitriding of aluminum has been investigated using marker and isotope sequence techniques in connection with ion-beam analysis. For an ion energy of 1 keV and a temperature of 400 °C, it is shown that the nitride grows at the surface with aluminum being supplied by diffusion from the underlying bulk. © 2000 American Institute of Physics.
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81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
61.72.up Other materials
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.80.Jh Ion radiation effects
61.82.Bg Metals and alloys

Electro-optic modulation in crystal-ion-sliced z-cut LiNbO3 thin films

Tarek A. Ramadan, M. Levy, and R. M. Osgood

Appl. Phys. Lett. 76, 1407 (2000); http://dx.doi.org/10.1063/1.126046 (3 pages) | Cited 28 times

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Electro-optic modulation is demonstrated in 10-μm-thick single-crystal LiNbO3 films obtained by crystal ion slicing. This technique uses ion implantation of single-crystal bulk samples followed by selective etching. The measured electro-optic response of these films is comparable, within experimental error, to that of single-crystal bulk LiNbO3 and is superior to previously reported values for epitaxial polycrystalline thin films. The product of half-wave voltage and modulator length, VπL, is 8 V cm. Post lift-off annealing is shown to be of key importance in improving the modulator extinction ratio. © 2000 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
61.82.Ms Insulators
61.72.up Other materials
42.79.Wc Optical coatings
61.72.Cc Kinetics of defect formation and annealing
81.65.Cf Surface cleaning, etching, patterning
61.80.Jh Ion radiation effects

A relation between surface oxide and oxygen-defect complexes in solid-phase epitaxial Si regrown from ion-beam-amorphized Si layers

Mihail P. Petkov, Claudine M. Chen, Harry A. Atwater, Stefano Rassiga, and Kelvin G. Lynn

Appl. Phys. Lett. 76, 1410 (2000); http://dx.doi.org/10.1063/1.126047 (3 pages) | Cited 3 times

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We present a direct evidence that ion implantation through thin (⩽5 nm) surface oxide layers is a source of O impurities, which form O-defect complexes during thermal treatment. The impurity-defect complexes are identified by correlating the results from positron annihilation spectroscopy, secondary-ion mass spectroscopy, and Monte Carlo simulations. The O atoms are introduced in the bulk by multiple recoil implantation by the primary ions. The signatures of large VmOn formations are observed at 800 °C, which implies the existence of smaller species at lower temperatures. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
61.82.Fk Semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.Yx Interaction between different crystal defects; gettering effect
61.80.Jh Ion radiation effects
78.70.Bj Positron annihilation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Gh Other heat and thermomechanical treatments

Depth analysis of buried iron disilicide formation by Fe ion implantation into Si

M. Walterfang, S. Kruijer, W. Keune, M. Dobler, and H. Reuther

Appl. Phys. Lett. 76, 1413 (2000); http://dx.doi.org/10.1063/1.126048 (3 pages) | Cited 1 time

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The depth distribution of the iron disilicide phases (α-FeSi2 and β-FeSi2) was investigated nondestructively by depth-selective conversion-electron Mössbauer spectroscopy after Fe+ implantation (200 keV, 3×1017 cm−2) and after subsequent rapid thermal annealing (RTA) at 900 °C for 30 s. The depth profiles of the two phases were found to be correlated with the Fe concentration profiles as determined by Auger electron sputter depth profiling. For the as-implanted state a broad distribution of a phase mixture of α- and β-FeSi2 is observed. Subsequent RTA induces a layered structure including a buried β-FeSi2 layer with a high phase content of 90% near 220 nm. © 2000 American Institute of Physics.
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61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities
76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.72.Cc Kinetics of defect formation and annealing

Observation of in-plane optical anisotropy of spin-cast rigid-rod electroluminescent polymer films

Carrie W. Y. Law, K. S. Wong, Z. Yang, L. E. Horsburgh, and A. P. Monkman

Appl. Phys. Lett. 76, 1416 (2000); http://dx.doi.org/10.1063/1.126049 (3 pages) | Cited 13 times

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Transmittance difference spectroscopy has been applied to study the optical properties of spin-cast rigid-rod polymer films. Significant in-plane optical anisotropy is observed for both the real and the imaginary parts of the transmittance of the poly(2,5-pyridine diyl) films. This in-plane optical anisotropy is a result of the partial alignment of the polymer chains, oriented radially outward from the center of the film, during the spin casting process. This observation has important implications for emissive polymer devices, particularly for devices sensitive to polarization direction and those using waveguide confinement where relatively long propagation distance within the films are required. © 2000 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
42.70.Jk Polymers and organics
85.60.Jb Light-emitting devices

Evolution of sp2 bonding with deposition temperature in tetrahedral amorphous carbon studied by Raman spectroscopy

M. Chhowalla, A. C. Ferrari, J. Robertson, and G. A. J. Amaratunga

Appl. Phys. Lett. 76, 1419 (2000); http://dx.doi.org/10.1063/1.126050 (3 pages) | Cited 94 times

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Two transitions in the bonding are found in tetrahedral amorphous carbon (ta-C) films as a function of deposition temperature. The total sp3 fraction shows a sharp decrease at a transition temperature of order 250 °C. In contrast, visible Raman finds that the sp2 sites show a gradual ordering into the graphitic clusters through the sharp bonding transition. The optical gap and resistivity show a similar, gradual transition. This indicates that the sp2 cluster size determines the optical gap, even when the sp2 content does not change. The Raman I(D)/I(G) peak ratio is found to vary inversely with the square of the gap. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.43.Er Other amorphous solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
68.60.Bs Mechanical and acoustical properties
71.23.-k Electronic structure of disordered solids
73.22.-f Electronic structure of nanoscale materials and related systems
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.ub Fullerenes and related materials

Direct evidence for interaction of magnesium with tris(8-hydroxy-quinoline) aluminum

P. He, Frederick C. K. Au, Y. M. Wang, L. F. Cheng, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 76, 1422 (2000); http://dx.doi.org/10.1063/1.126051 (3 pages) | Cited 29 times

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The interaction between magnesium (Mg) and tris(8-hydroxy-quinoline) aluminum (Alq3) has been studied using high-resolution electron energy-loss spectroscopy (HREELS). It was found that deposition of magnesium on the Alq3 film gave rise to clear changes in the HREELS spectra. The changes are attributed to the weakly bounded Mg atoms on the Alq3 layer. Interestingly, for a given amount of magnesium (Mg to Al atoms ratio=3) on Alq3 film, remarkable changes were observed in the HREELS spectra when the sample was heated. A loss peak at 81 meV, which was assigned to Mg–O stretch mode, appeared upon annealing and increased in intensity as the annealing temperature increased up to about 360 K. This suggested that the diffusion of Mg atoms into the Alq3 layer and the reaction between Mg and Alq3 molecule occurred at the temperature range investigated. The present work has provided direct evidence for the strong interaction between magnesium and Alq3. © 2000 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
79.20.Kz Other electron-impact emission phenomena

Strain-dependent electrical resistance of tin-doped indium oxide on polymer substrates

Darran R. Cairns, Richard P. Witte, Daniel K. Sparacin, Suzanne M. Sachsman, David C. Paine, Gregory P. Crawford, and R. R. Newton

Appl. Phys. Lett. 76, 1425 (2000); http://dx.doi.org/10.1063/1.126052 (3 pages) | Cited 146 times

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The increase in sheet resistance of indium–tin–oxide (ITO) films on polyethylene terephthalate with increasing tensile strain is reported. The increase in resistance is related to the number of cracks in the conducting layer which depends upon applied strain and film thickness. We propose a simple model that describes the finite but increasing resistance in the cracked ITO layer in terms of a small volume of conducting material within each crack. © 2000 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
68.55.-a Thin film structure and morphology
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