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3 Dec 2001

Volume 79, Issue 23, pp. 3749-3889

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Electrical activation of B in the presence of boron-interstitials clusters

Giovanni Mannino, Sandro Solmi, Vittorio Privitera, and Massimo Bersani

Appl. Phys. Lett. 79, 3764 (2001); http://dx.doi.org/10.1063/1.1423775 (3 pages) | Cited 5 times

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Boron marker-layer structures have been used to analyze the evolution of boron-interstitial clusters (BICs) formed during transient enhanced diffusion. Our approach is based on the measure of B activation by spreading resistance profiling after annealing of Si implantation damage. We investigated a wide range of implant conditions in terms of defect densities below and above the amorphization threshold of Si. We found a common behavior of BICs in terms of trapping and release processes of B atoms. The BICs density as a function of time for different concentration ratios of I and B has been determined. © 2001 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uf Ge and Si
71.55.Cn Elemental semiconductors
66.30.J- Diffusion of impurities
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters

Band-gap energies of sol-gel-derived SrTiO3 thin films

Dinghua Bao, Xi Yao, Naoki Wakiya, Kazuo Shinozaki, and Nobuyasu Mizutani

Appl. Phys. Lett. 79, 3767 (2001); http://dx.doi.org/10.1063/1.1423788 (3 pages) | Cited 58 times

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Band-gap energies of sol-gel-derived SrTiO3 thin films were studied in terms of annealing temperature and film thickness. The band-gap energies of highly crystallized films were comparable to those of single crystals reported, whereas for poor-crystallized films, their band-gap energy values were much larger than those of single crystals. The larger band-gap energy shift was believed to be mainly due to both quantum size effect and existence of amorphous phase in thin films. The band-gap energies also showed a strong dependence on film thickness. There was a critical film thickness (∼200 nm), above which the films had band-gap energies close to those of crystals or bulks, but below that, the values shifted largely, which can be attributed to the influence of crystallinity of thin films. Such a thickness effect of band-gap energy should be of high interest in optical device applications. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
71.20.Ps Other inorganic compounds
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
42.70.-a Optical materials

Near-infrared electroluminescence from conjugated polymer/lanthanide porphyrin blends

Benjamin S. Harrison, Timothy J. Foley, Mohamed Bouguettaya, James M. Boncella, John R. Reynolds, Kirk S. Schanze, Joonbo Shim, Paul H. Holloway, G. Padmanaban, and S. Ramakrishnan

Appl. Phys. Lett. 79, 3770 (2001); http://dx.doi.org/10.1063/1.1421413 (3 pages) | Cited 55 times

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Near-infrared-emitting polymer light-emitting diodes (PLEDs) have been fabricated using blends of conjugated polymers and lanthanide tetraphenylporphyrin complexes. Host polymers include MEH–PPV and a bis-alkoxy-substituted poly(p-phenylene) (PPP–OR11), and the lanthanide complexes include Yb(TPP)acac and Er(TPP)acac (where TPP = 5,10,15,20-tetraphenylporphyrin and acac=acetylacetonate). Electroluminescence (EL) is observed at 977 nm from devices fabricated using MEH–PPV or PPP–OR11 blended with Yb(TPP)acac, and EL is observed at 1560 nm from a device fabricated using a blend of MEH–PPV and Er(TPP)acac. Visible EL from the host polymers is strongly suppressed in all of the devices, however, in the device fabricated using the PPP–OR11 polymer blue emission from the host is completely quenched. Very efficient quenching of the EL from the host in the PPP–OR11 device is believed to occur due to efficient Förster energy transfer, which is facilitated by the excellent spectral overlap between the PPP–OR11 fluorescence and the Soret absorption band of the TPP ligand. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices

Amorphous carbon nanowires investigated by near-edge-x-ray-absorption-fine-structures

Y. H. Tang, P. Zhang, P. S. Kim, T. K. Sham, Y. F. Hu, X. H. Sun, N. B. Wong, M. K. Fung, Y. F. Zheng, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 79, 3773 (2001); http://dx.doi.org/10.1063/1.1425462 (3 pages) | Cited 16 times

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The structure and bonding of amorphous carbon nanowires and amorphous carbon nanowires-converted multiwalled carbon nanotubes have been investigated with carbon K-edge near-edge x-ray absorption fine structure using surface-sensitive total electron yield, and bulk-sensitive fluorescence yield. The results strongly support that amorphous carbon nanowire is a precursor to multiwalled carbon nanotubes. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
61.43.Er Other amorphous solids
78.70.Dm X-ray absorption spectra

Intrinsic stress evolution in aluminum nitride thin films and the influence of multistep processing

Ashok Rajamani, Rod Beresford, and Brian W. Sheldon

Appl. Phys. Lett. 79, 3776 (2001); http://dx.doi.org/10.1063/1.1420774 (3 pages) | Cited 13 times

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Curvature measurements were used to investigate intrinsic stresses in AlN thin films grown by molecular beam epitaxy. In situ stress evolution experiments show that tensile stress is generated at the time where individual islands coalesce into a continuous film, and for some time after coalescence. Compressive stress is also generated both before and after coalescence. Introducing an intermediate annealing stage appears to reduce tensile stress evolution after coalescence, ultimately increasing the final intrinsic compressive stress. The maximum reduction in the tensile intrinsic stress is obtained when the sample is annealed at roughly the time where the islands coalesce into a continuous film.© 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Photoluminescence of GaN grown by molecular-beam epitaxy on a freestanding GaN template

M. A. Reshchikov, D. Huang, F. Yun, L. He, H. Morkoç, D. C. Reynolds, S. S. Park, and K. Y. Lee

Appl. Phys. Lett. 79, 3779 (2001); http://dx.doi.org/10.1063/1.1421421 (3 pages) | Cited 19 times

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Photoluminescence (PL) studies were performed on a 1.5-μm-thick GaN layer grown by molecular-beam epitaxy on a freestanding GaN template that in turn was grown by hydride vapor-phase epitaxy. PL spectra from both the epilayer and the substrate contain a plethora of sharp peaks related to excitonic transitions. We identified the main peaks in the PL spectrum. Taking advantage of the observation of donor bound exciton peaks and their associated two-electron satellites, we have determined the binding energies of two distinct shallow donors (28.8 and 32.6 meV), which are attributed to Si and O, respectively. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology

Microstructure and optical properties of scandium oxide thin films prepared by metalorganic chemical-vapor deposition

Z. Xu, A. Daga, and Haydn Chen

Appl. Phys. Lett. 79, 3782 (2001); http://dx.doi.org/10.1063/1.1424072 (3 pages) | Cited 9 times

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Dense, high-index, and reproducible scandium oxide (Sc2O3) thin films with high mechanical strength were grown on glass substrates by metalorganic chemical-vapor deposition. The influence of deposition temperature on the microstructure evolution and optical properties of Sc2O3 thin films was investigated by x-ray diffraction, scanning electron microscopy, atomic-force microscopy, transmission electron microscopy, and spectrophotometry. A close relationship between microstructure and optical properties was found for Sc2O3 thin films prepared at different deposition temperatures. © 2001 American Institute of Physics.
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78.66.Nk Insulators
42.79.Wc Optical coatings
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.60.Bs Mechanical and acoustical properties
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Ha Other nonmetallic inorganics

Reversible photoinduced spectral change in Eu2O3 at room temperature

Shosuke Mochizuki, Tauto Nakanishi, Yuya Suzuki, and Kimihiro Ishi

Appl. Phys. Lett. 79, 3785 (2001); http://dx.doi.org/10.1063/1.1425064 (3 pages) | Cited 20 times

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When Eu2O3 powder compact and film are irradiated with ultraviolet (UV) laser light in a vacuum, their photoluminescence (PL) spectra change from a red sharp-line structure to a white broad band, which can be clearly seen with the naked eye. After removing the UV laser light, the white PL continues for more than several months at room temperature under room light, in spite of any changes of atmosphere. By irradiating with the same UV laser light at room temperature under O2 gas atmosphere, the original red PL state reappears. Such a reversible phenomenon may well yield materials for white-light-emitting devices and erasable optical storage. © 2001 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.70.Ln Holographic recording materials; optical storage media
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.66.Nk Insulators
61.82.Ms Insulators

Influence of Mg doping on structural defects in AlGaN layers grown by metalorganic chemical vapor deposition

Hyung Koun Cho, Jeong Yong Lee, Seong Ran Jeon, and Gye Mo Yang

Appl. Phys. Lett. 79, 3788 (2001); http://dx.doi.org/10.1063/1.1424471 (3 pages) | Cited 8 times

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Influence of Mg doping on structural defects in Al0.13Ga0.87N layers grown on sapphire substrates by metalorganic chemical vapor deposition were studied using transmission electron microscopy. By increasing the Mg source flow rate, the reduction of dislocation density occurred up to the Mg source flow rate of 0.103 μmol/min. While the vertical type inversion domain boundaries (IDBs) were observed in the Al0.13Ga0.87N layers grown with the low Mg source flow rate, the IDBs in the Al0.13Ga0.87N layers grown with the high Mg source flow rate have horizontally multifaceted shapes. The change of polarity by the IDBs of horizontal type also resulted in the 180° rotation of pyramidal defects within the same AlGaN layer. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.uj III-V and II-VI semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect

Thermoelectric figure of merit for parallel transport in superlattices

V. B. Antonyuk, A. G. Mal’shukov, Zhongshui Ma, and K. A. Chao

Appl. Phys. Lett. 79, 3791 (2001); http://dx.doi.org/10.1063/1.1421083 (3 pages)

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We have calculated the thermoelectric figure of merit of a superlattice with the temperature gradient and the electric field applied parallel to the interfaces. Including the heat flow between the barriers and the wells, we have derived the temperature distribution in the sample, from which the expressions of the resultant thermal conductivity and hence the figure of merit are obtained. Our numerical result provides relevant information for achieving a high figure of merit. © 2001 American Institute of Physics.
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73.50.Lw Thermoelectric effects
73.63.-b Electronic transport in nanoscale materials and structures

Polariton and free-exciton-like photoluminescence in ZnO

D. C. Reynolds, D. C. Look, B. Jogai, and T. C. Collins

Appl. Phys. Lett. 79, 3794 (2001); http://dx.doi.org/10.1063/1.1412435 (3 pages) | Cited 35 times

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An unusual photoluminescence line X has been observed in ZnO at an energy between that of the common donor-bound excitons (DBEs) and the free excitons (FEs). In the presence of a high carrier concentration, induced by a second below-band gap laser, the DBEs decrease in intensity, due to screening, and both the FEs and X increase. Thus, X has free-exciton, rather than bound-exciton, character. However, its electric-field vector lies in the plane perpendicular to the c axis, as is also found for the DBEs. The appearance of X is discussed in terms of the polariton picture. © 2001 American Institute of Physics.
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78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
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