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9 Dec 2002

Volume 81, Issue 24, pp. 4499-4663

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Fabrication technique for filling-factor tunable titanium dioxide colloidal crystal replicas

Suzushi Nishimura, Atsushi Shishido, Neal Abrams, and Thomas E. Mallouk

Appl. Phys. Lett. 81, 4532 (2002); http://dx.doi.org/10.1063/1.1524693 (3 pages) | Cited 14 times

Online Publication Date: 3 December 2002

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Filling-factor tunable titanium dioxide replicas of colloidal crystals were fabricated by using a liquid phase deposition (LPD) technique. Ammonium hexafluorotitanate [(NH4)2TiF6] was used as a precursor, which was converted slowly to titanium dioxide by hydrolysis with boric acid. After the oxide was formed in voids of latex colloidal crystals, the latex was removed by calcination. By applying the LPD process to the replica again, the filling factor of the replica could be increased in a controllable fashion. With 203 nm template spheres, the peak shift in the ∼ 490 nm stop band depended linearly on the deposition time for the first 20 min, at a rate of 4.4 nm/min. Thus the position of the Bragg reflection peak could be adjusted precisely by controlling the filling factor of the replica structure. © 2002 American Institute of Physics.
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42.86.+b Optical workshop techniques
42.70.Qs Photonic bandgap materials
82.70.Dd Colloids
42.50.-p Quantum optics
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
81.40.Gh Other heat and thermomechanical treatments
78.20.-e Optical properties of bulk materials and thin films

Images of dopant profiles in low-energy scanning transmission electron microscopy

P. G. Merli, F. Corticelli, and V. Morandi

Appl. Phys. Lett. 81, 4535 (2002); http://dx.doi.org/10.1063/1.1528734 (3 pages) | Cited 7 times

Online Publication Date: 3 December 2002

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A scanning electron microscope is used in transmission mode. The image is formed with secondary electrons, collected by the standard detector, resulting from the conversion of transmitted electrons on a circular disk, covered with MgO smoke, located below the thinned specimen, and centered on the optical axis. Operating in this mode, bright-field images of As dopant profiles in Si, having a peak concentrations of 5 and 2.5 at. % and a spatial extension of about 40 nm, have been observed in cross sectioned specimens. The description of the dopant profiles has a resolution of 6 nm as defined by the spot size of the microscope, equipped with a LaB6 tip, and operating at 30 keV. © 2002 American Institute of Physics.
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61.72.S- Impurities in crystals
81.70.Jb Chemical composition analysis, chemical depth and dopant profiling
68.37.Lp Transmission electron microscopy (TEM)

Atomic structure of steps and defects on the clean diamond (100)-2×1 surface studied using ultrahigh vacuum scanning tunneling microscopy

R. E. Stallcup and J. M. Perez

Appl. Phys. Lett. 81, 4538 (2002); http://dx.doi.org/10.1063/1.1527697 (3 pages) | Cited 4 times

Online Publication Date: 3 December 2002

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We report ultrahigh vacuum scanning tunneling microscopy studies of the clean nonhydrogen-terminated diamond (100)-2×1 surface showing single- and double-layer steps that are rebonded. The main defects observed are single, multiple, and row dimer vacancies, and antiphase boundaries. Buckling of dimers is not observed, consistent with symmetric dimers. © 2002 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.U- Carbon/carbon-based materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.05.Cy Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
61.72.J- Point defects and defect clusters

Observation of coreless edge and mixed dislocations in Mg-doped Al0.03Ga0.97N

D. Cherns, Y. Q. Wang, R. Liu, and F. A. Ponce

Appl. Phys. Lett. 81, 4541 (2002); http://dx.doi.org/10.1063/1.1527978 (3 pages) | Cited 11 times

Online Publication Date: 3 December 2002

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Transmission electron microscopy has been used to examine the core structure of threading dislocations in heavily Mg-doped Al0.03Ga0.97N thin films. It is shown that edge and mixed, but not screw, dislocations have hollow cores with diameters typically 1–5 nm. A model is presented where hollow core formation is initiated by the segregation and subsequent precipitation of Mg at these dislocation cores. The implications for understanding the formation of hollow core dislocations in other GaN films are discussed. © 2002 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
64.75.-g Phase equilibria

Extraction of height–height correlation function of random surfaces from the average intensity of image speckles

Chuanfu Cheng, Shuyun Teng, Man Liu, Shangqing Gong, Ruxin Li, and Zhizhan Xu

Appl. Phys. Lett. 81, 4544 (2002); http://dx.doi.org/10.1063/1.1528728 (3 pages) | Cited 1 time

Online Publication Date: 3 December 2002

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We present a method for the extraction of the height–height correlation function of random surfaces from the average intensity of image speckles. The setup of a Fourier transforming and imaging system with a variable aperture is used for both the theoretical analysis and experimental performances. Based on the analytical expression of the image intensity, an algorithm is developed to formulate numerically the intensity data versus the aperture radius into the pair of Bessel–Fourier transform and the inversion, from which the height–height correlation function is reconstructed. Three samples of Gaussian correlation are used for the experimental demonstration. The extracted height–height correlation function and the random surface parameters obtained thereby conform with those obtained by atomic force microscopy. © 2002 American Institute of Physics.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
68.37.Ps Atomic force microscopy (AFM)

Highly crystalline 5H-polytype of sp3-bonded boron nitride prepared by plasma-packets-assisted pulsed-laser deposition: An ultraviolet light emitter at 225 nm

Shojiro Komatsu, Keiji Kurashima, Hisao Kanda, Katsuyuki Okada, Mamoru Mitomo, Yusuke Moriyoshi, Yoshiki Shimuzu, Masaharu Shiratani, Toshiki Nakano, and Seiji Samukawa

Appl. Phys. Lett. 81, 4547 (2002); http://dx.doi.org/10.1063/1.1527987 (3 pages) | Cited 14 times

Online Publication Date: 3 December 2002

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Highly crystalline 5H-polytypic form of sp3-bonded boron nitride (BN) was grown by pulsed-laser-vaporization of BN, where synchronous reactive-plasma packets assisted the crystal growth in the vapor phase. The structure of the product crystallites (∼5 μm) was confirmed by using transmission electron diffraction and electron energy loss spectroscopy. This material proved to have a sharp and dominant band at 225 nm by cathodoluminescence at room temperatures and corresponding monochromatic images revealed that they uniformly emitted the ultraviolet light. Considering that cubic BN has already been doped as p- and n-type semiconductors, this material may be applied to the light-emitting devices working at almost the deepest limit of the UV region that is functional without vacuum. © 2002 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.10.Bk Growth from vapor
81.15.Fg Pulsed laser ablation deposition
78.60.Hk Cathodoluminescence, ionoluminescence
52.77.Dq Plasma-based ion implantation and deposition
79.20.Uv Electron energy loss spectroscopy
42.72.Bj Visible and ultraviolet sources
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