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12 Dec 2005

Volume 87, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 87, 243101 (2005); http://dx.doi.org/10.1063/1.2147713 (3 pages)

Y.-S. Choi, K. Hennessy, R. Sharma, E. Haberer, Y. Gao, S. P. DenBaars, S. Nakamura, E. L. Hu, and C. Meier
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Homogenization of the melting depth in SiC on Si structures during flash lamp irradiation

Matthias Voelskow, Wolfgang Skorupa, Mark P. Smith, and Richard A. McMahon

Appl. Phys. Lett. 87, 241901 (2005); http://dx.doi.org/10.1063/1.2140485 (3 pages) | Cited 3 times

Online Publication Date: 5 December 2005

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Flash lamp annealing of heteroepitaxial silicon carbide on silicon structures involves melting the silicon below the SiC layer but the faceted nature of the liquid-solid interface leads to unacceptable surface roughness. This letter describes a method of controlling melting by using a melt stop created at a controlled depth below the Si/SiC interface by implanting a high dose of carbon, which significantly increases the silicon melting temperature. Results confirm the effectiveness of this approach for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques.
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81.65.-b Surface treatments
61.72.Cc Kinetics of defect formation and annealing
68.47.Fg Semiconductor surfaces
64.70.D- Solid-liquid transitions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Anisotropy in periodic mesoporous silica and organosilica films studied by generalized ellipsometry

F. C. Peiris, B. D. Hatton, G. A. Ozin, and D. D. Perovic

Appl. Phys. Lett. 87, 241902 (2005); http://dx.doi.org/10.1063/1.2140472 (3 pages) | Cited 7 times

Online Publication Date: 5 December 2005

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The dielectric functions of a series of periodic mesoporous silica as well as periodic mesoporous organosilica thin films were measured using generalized variable angle spectroscopic ellipsometry over the spectral range 300–1400 nm. Ellipsometry results indicate that following template removal, both types of films possess uniaxial anisotropy, with the optic axis perpendicular to the plane of the film. This anisotropy is apparently caused by the structural distortion of the channels, oriented primarily parallel to the substrate plane. We also find that the birefringence increases as a function of porosity.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
78.20.Fm Birefringence

Reduction of damage threshold in dielectric materials induced by negatively chirped laser pulses

E. Louzon, Z. Henis, S. Pecker, Y. Ehrlich, D. Fisher, M. Fraenkel, and A. Zigler

Appl. Phys. Lett. 87, 241903 (2005); http://dx.doi.org/10.1063/1.2140476 (3 pages) | Cited 9 times

Online Publication Date: 5 December 2005

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The threshold fluence for laser induced damage in wide band gap dielectric materials, fused silica and MgF2, is observed to be lower by up to 20% for negatively (down) chirped pulses than for positively (up) chirped, at pulse durations ranging from 60 fs to 1 ps. This behavior of the threshold fluence for damage on the chirp direction was not observed in semiconductors (silicon and GaAs). Based on a model including electron generation in the conduction band and Joule heating, it is suggested that the decrease in the damage threshold for negatively chirped pulse is related to the dominant role of multiphoton ionization in wide gap materials.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
77.22.Jp Dielectric breakdown and space-charge effects
61.82.Ms Insulators
61.82.Fk Semiconductors

Contributions to the homogeneous plastic flow of in situ metallic glass matrix composites

X. L. Fu, Y. Li, and C. A. Schuh

Appl. Phys. Lett. 87, 241904 (2005); http://dx.doi.org/10.1063/1.2140477 (3 pages) | Cited 4 times

Online Publication Date: 5 December 2005

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The homogeneous deformation of Zr-based bulk metallic glass composites is studied near the glass transition temperature, at various levels of reinforcement volume fraction. Through examination of the constitutive response, it is seen that the presence of in situ reinforcements increases the flow resistance of the glass dramatically. This strengthening effect is shown to arise from two separate contributions: load transfer from the amorphous matrix to the reinforcements, and changes to the glass composition and structure upon in situ precipitation of reinforcements.
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81.05.Pj Glass-based composites, vitroceramics
61.43.Fs Glasses
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Transmission electron microscopy study on ion-beam-synthesized amorphous Fe–Si thin layers

Muneyuki Naito, Manabu Ishimaru, Yoshihiko Hirotsu, James A. Valdez, and Kurt E. Sickafus

Appl. Phys. Lett. 87, 241905 (2005); http://dx.doi.org/10.1063/1.2142101 (3 pages) | Cited 10 times

Online Publication Date: 6 December 2005

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Ion-beam-synthesized amorphous Fe–Si thin layers have been characterized using transmission electron microscopy (TEM) in combination with imaging plate techniques. Si single crystals with a (111) orientation were irradiated with 120 keV Fe+ ions to a fluence of 4.0×1017 cm−2 at cryogenic temperature (120 K). Cross-sectional TEM observations indicated the formation of an amorphous bilayer on the topmost layer of the Si substrate. It was found that the upper layer is an amorphous Fe–Si with the composition, in terms of atomic ratio, of Fe/Si ∼ 1/2, while the lower one is an amorphous Si. Atomic pair-distribution functions extracted from microbeam electron diffraction patterns revealed that the nature of short-range order in amorphous Fe–Si thin layer can be well described by the atomic arrangements of crystalline iron silicides.
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61.43.Er Other amorphous solids
61.80.Jh Ion radiation effects
61.82.-d Radiation effects on specific materials
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)

Deep-ultraviolet micro-Raman investigation of surface defects in a 4H–SiC homoepitaxially grown film

Takuro Tomita, Shigeki Matsuo, Tatsuya Okada, Tsunenobu Kimoto, Hiroyuki Matsunami, Takeshi Mitani, and Shin-Ichi Nakashima

Appl. Phys. Lett. 87, 241906 (2005); http://dx.doi.org/10.1063/1.2142080 (3 pages)

Online Publication Date: 6 December 2005

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The structures of comet defects in a 4H–SiC homoepitaxially grown film are investigated by deep-ultraviolet micro-Raman spectroscopy. Spatial distribution of the 4H- and 3C–SiC is clearly distinguished both from the intensities of the folded longitudinal acoustic phonon mode and the peak energies of the nonfolded longitudinal optical phonon mode. The mappings of these parameters indicate the existence of two types of comets. The mechanisms of heteropolytypic inclusion in comets are discussed.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
63.20.-e Phonons in crystal lattices
78.30.Hv Other nonmetallic inorganics

Application of synchrotron x-ray microtomography to investigate ductile fracture in Al alloys

L. Qian, H. Toda, K. Uesugi, T. Kobayashi, T. Ohgaki, and M. Kobayashi

Appl. Phys. Lett. 87, 241907 (2005); http://dx.doi.org/10.1063/1.2142081 (3 pages) | Cited 15 times

Online Publication Date: 6 December 2005

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The in situ high-resolution synchrotron x-ray computed microtomography has been applied to visualize and quantify the ductile fracture process of a notched Al alloy specimen. The three-dimensional (3D) investigation reveals that voids are nucleated, grow and coalesce more easily near the notch front and in the central region of the sample. These voids are mainly associated with Si particles in the eutectic (EU) phase. The 3D packing architecture of particles in the EU region, and the 3D morphology of α phase are also visualized. The feasibility of this technique highlights the potential of its application in the field of micromechanics-based fracture.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Thermal transport properties of thin films of small molecule organic semiconductors

Namsu Kim, Benoit Domercq, Seunghyup Yoo, Adam Christensen, Bernard Kippelen, and Samuel Graham

Appl. Phys. Lett. 87, 241908 (2005); http://dx.doi.org/10.1063/1.2140478 (3 pages) | Cited 12 times

Online Publication Date: 6 December 2005

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A series of harmonic Joule-heating experiments have been employed to determine the thermal conductivities of thin films of pentacene, N,N′-diphenyl−N,N′-di(3-methylphenyl)−(1,1′-biphenyl)-4,4′-diamine, and tris(8-hydroquinolinato)aluminum, three widely used organic semiconductors. Room-temperature thermal conductivity values of 0.51, 0.24, and 0.48 W/mK were measured for films of these three compounds, respectively. These values are over two orders of magnitude lower than those of inorganic semiconductors. While amorphous films were found to display only small thermal conductivity changes over the temperature range of 228–350 K, pentacene exhibited stronger variations that are typical of phonon-phonon scattering observed in polycrystalline semiconductors.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.20.K- Phonon interactions

Origin of pseudoelastic behavior in Ti–Mo-based alloys

L. C. Zhang, T. Zhou, S. P. Alpay, M. Aindow, and M. H. Wu

Appl. Phys. Lett. 87, 241909 (2005); http://dx.doi.org/10.1063/1.2142089 (3 pages) | Cited 12 times

Online Publication Date: 7 December 2005

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High-resolution transmission electron microscopy and in situ x-ray diffraction analyses have been used to elucidate the compositional sensitivity of the deformation behavior in two β‐Ti–Mo-based alloys. The alloy with 8% Mo exhibited conventional elastic∕plastic behavior in tension which corresponds to the irreversible formation of stress-induced orthorhombic α″ martensite. The alloy with 10% Mo exhibited a pronounced pseudoelastic response with recovery of ≈ 80% of the imposed tensile strain. This phenomenon is associated with the formation of another orthorhombic martensitic phase, which has not been reported previously, and this nucleates from pre-existing domains in the β matrix.
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81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.66.Dk Alloys
64.60.Q- Nucleation
68.37.Lp Transmission electron microscopy (TEM)
82.80.-d Chemical analysis and related physical methods of analysis

Electrically conductive polyaniline-sulfonated poly(arylene ether sulfone) composites

N. D. Sankir, R. O. Claus, J. B. Mecham, and W. L. Harrison

Appl. Phys. Lett. 87, 241910 (2005); http://dx.doi.org/10.1063/1.2142093 (2 pages) | Cited 3 times

Online Publication Date: 7 December 2005

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Electrically conductive composite films from sulfonated poly(arylene ether sulfone) and polyaniline emeraldine base were prepared. The electrical conductivity values, which would be useful for a wide range of applications, were achieved after only 1 min of doping in protonic acid solution. A molecular interaction between the supportive matrix and conductive filler is inferred based on significant difference in the Fourier-transform infrared spectra of the doped and undoped composite films.
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81.05.Qk Reinforced polymers and polymer-based composites
73.61.Ph Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.66.Qn Polymers; organic compounds
78.30.Jw Organic compounds, polymers

Reduction of threading dislocations in AlGaN layers grown on AlN/sapphire templates using high-temperature GaN interlayer

H. Jiang, T. Egawa, M. Hao, and Y. Liu

Appl. Phys. Lett. 87, 241911 (2005); http://dx.doi.org/10.1063/1.2143126 (3 pages) | Cited 12 times

Online Publication Date: 7 December 2005

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Crack-free AlGaN layers were grown on AlN/sapphire templates by low-pressure metalorganic chemical vapor deposition. Reduction of threading-dislocation (TD) density is achieved by inserting a high-temperature GaN interlayer between the AlGaN and AlN layers. Structural characterization reveals that such an interlayer can efficiently block the TDs propagating from the underlying AlN layer, and reduce the TD density in the subsequent AlGaN layer by one order of magnitude with an optimum thickness of 25 nm. It is also clarified that the decrease of edge TDs is the dominant contribution to this reduction.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Strong green upconversion emission in ZrO2:Yb3+–Ho3+ nanocrystals

E. De la Rosa, P. Salas, H. Desirena, C. Angeles, and R. A. Rodríguez

Appl. Phys. Lett. 87, 241912 (2005); http://dx.doi.org/10.1063/1.2143131 (3 pages) | Cited 33 times

Online Publication Date: 7 December 2005

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Structural and upconversion emission properties of ZrO2:Yb3+–Ho3+ nanocrystals were analyzed as function of Yb3+ concentration. Structural characterization shows a crystallite size up to 80 nm and tetragonal and cubic phase as the main crystalline structures. Strong green (540 nm) and weak red (670 nm) and near infrared (760 nm) emission bands were observed with 968 nm excitation. The upconversion is based on two photons absorption either by the energy transfers from Yb3+ ion or by the excited state absorption. The energy transfer efficiency was calculated to be 50% for 2 mol % of Yb3+ diminishing to less than 20% for higher concentration. The Yb3+ concentration also affects the decay time of the green emission of Ho3+ ion diminishing from 140 μs for 2 mol % of Yb to 76 μs for higher concentration.
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78.55.Hx Other solid inorganic materials

Electro-optical switching of a thin antiferroelectric liquid crystal film in the planar geometry with evaporated top electrode

L. M. Blinov, A. R. Geivandov, V. V. Lazarev, S. P. Palto, S. G. Yudin, G. Pelzl, and W. Weissflog

Appl. Phys. Lett. 87, 241913 (2005); http://dx.doi.org/10.1063/1.2143134 (2 pages) | Cited 4 times

Online Publication Date: 7 December 2005

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An antiferroelectric liquid crystal phase formed by bent-shape molecules was investigated in a geometry typical of solid-state technology. A thin Langmuir film of the compound was transferred onto a conductive glass and supplied with a top electrode evaporated in vacuum. Upon heating the sandwich keeps its integrity even in a high-temperature B2 phase which, despite strong confinement, manifests antiferroelectric and electrooptic properties similar to those in bulk samples. This approach fills the gap between investigations of solid and liquid crystal ferroelectrics and open new ways for studying dielectric, ferro- and antiferroelectric properties of thin and ultrathin films of liquid crystals.
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61.30.-v Liquid crystals
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
42.70.Df Liquid crystals
78.20.Jq Electro-optical effects
77.80.Fm Switching phenomena
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.15.+e Liquid thin films
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Gh Other heat and thermomechanical treatments

Enhancement of Pr3+ luminescence in PbO–GeO2 glasses containing silver nanoparticles

Luz Patrícia Naranjo, Cid B. de Araújo, Oscar L. Malta, Petrus A. Santa Cruz, and Luciana R. P. Kassab

Appl. Phys. Lett. 87, 241914 (2005); http://dx.doi.org/10.1063/1.2143135 (3 pages) | Cited 44 times

Online Publication Date: 7 December 2005

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Pr3+-doped PbO–GeO2 (PGO) glasses containing silver nanoparticles (NPs) were prepared and their spectroscopic characteristics were studied. The PGO samples and the nucleation of silver NP were obtained melting the starting oxide powders, quenching and annealing. Transmission electron microscopy was used to characterize the NP size distribution. Isolated silver particles with average diameter of 2 nm and aggregates with dimensions smaller than 100 nm were observed. Optical absorption and luminescence experiments were performed to investigate the properties of the composite system. Enhancement of the Pr3+ ions’ luminescence was observed due to the presence of the silver NP.
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81.05.Pj Glass-based composites, vitroceramics
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.55.Qr Amorphous materials; glasses and other disordered solids
78.40.Pg Disordered solids
61.72.up Other materials
64.70.D- Solid-liquid transitions
81.40.Gh Other heat and thermomechanical treatments
68.37.Lp Transmission electron microscopy (TEM)

Hydrogen-induced modification of the medium-range structural order in amorphous silicon films

L. N. Nittala, S. Jayaraman, B. A. Sperling, and J. R. Abelson

Appl. Phys. Lett. 87, 241915 (2005); http://dx.doi.org/10.1063/1.2143124 (3 pages) | Cited 8 times

Online Publication Date: 7 December 2005

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We use fluctuation electron microscopy to determine changes in the medium-range structural order of un-hydrogenated amorphous silicon thin films after they are exposed to atomic hydrogen at a substrate temperature of 230 °C. The films are deposited by magnetron sputtering at either 230 or 350 °C substrate temperature to obtain starting states with small or large initial medium-range order, respectively. The in-diffusion of atomic hydrogen causes the medium-range order to decrease for the small initial order but to increase for the large initial order. We suggest that this behavior can be understood in terms of classical nucleation theory: The ordered regions of small diameter are energetically unstable and can lower their energy by evolving towards a continuous random network, whereas the ordered regions of large diameter are energetically stable and can lower their energy by coarsening towards the nanocrystalline state.
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81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
66.30.-h Diffusion in solids

Direct evidence of 8:9 commensurate heterojunction formed between InN and AlN on c plane

C.-L. Wu, C.-H. Shen, H.-W. Lin, H.-M. Lee, and S. Gwo

Appl. Phys. Lett. 87, 241916 (2005); http://dx.doi.org/10.1063/1.2146062 (3 pages) | Cited 17 times

Online Publication Date: 7 December 2005

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We show that, despite a large difference in lattice constants, high-quality InN/AlN heterostructures can be formed on Si(111) due to the existence of “magic” ratios between the lattice constants of comprising material pairs: 2:1 (Si/Si3N4), 5:4 (AlN/Si), and 8:9 (InN/AlN). For InN growth on AlN with nitrogen polarity, by using reflection high-energy electron diffraction and cross-sectional transmission electron microscopy, we have found that the pseudomorphic to commensurate lattice transition occurs within the first monolayer of growth, resulting in an abrupt heterojunction at the atomic scale. This new route of lattice match allows the formation of commensurate and nearly strain-free interface with a common two-dimensional superlattice.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Ea III-V semiconductors
64.70.Rh Commensurate-incommensurate transitions
68.65.Cd Superlattices
64.70.K- Solid-solid transitions
68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

ZnO nanoclusters: Synthesis and photoluminescence

J. Antony, X. B. Chen, J. Morrison, L. Bergman, Y. Qiang, D. E. McCready, and M. H. Engelhard

Appl. Phys. Lett. 87, 241917 (2005); http://dx.doi.org/10.1063/1.2147715 (3 pages) | Cited 22 times

Online Publication Date: 7 December 2005

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ZnO nanoclusters were prepared and deposited at room temperature using a newly developed cluster source. The nanoclusters act as a building block for the cluster films deposited on various substrates. The cluster films were characterized by transmission electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and photoluminescence. We prepared monodispersed crystalline ZnO nanoclusters of ∼ 7 nm diameter. These clusters have a significant blueshift of ∼ 125 meV (compared to the results published so far) within the ultraviolet region at room temperature. No PL in our samples was observed in the visible region, which implies negligible defect formation in ZnO nanocluster films.
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81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
78.66.Hf II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.16.-c Methods of micro- and nanofabrication and processing
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.40.Fy Semiconductors

Time-resolved experimental study of carrier lifetime in GaN epilayers

J. Mickevičius, M. S. Shur, R. S. Qhalid Fareed, J. P. Zhang, R. Gaska, and G. Tamulaitis

Appl. Phys. Lett. 87, 241918 (2005); http://dx.doi.org/10.1063/1.2146061 (3 pages) | Cited 8 times

Online Publication Date: 8 December 2005

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Time-resolved photoluminescence and light-induced transient grating measurements of GaN epilayers show that the photoluminescence decay can be described by two coupled exponential terms and that carrier mobility and lifetime in GaN epilayers are correlated within the model which accounts for nonradiative carrier recombination predominantly at dislocations. The obtained results demonstrate that migration-enhanced metalorganic chemical vapor deposition (MEMOCVD™) allows for growth of high-quality GaN epilayers on sapphire substrates with the dislocation density close to 108 cm−2, carrier lifetime as long as 2 ns, and ambipolar diffusion coefficient of 2.1 cm2 s−1 corresponding to the hole mobility of approximately 40 cm2 V−1 s−1.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
66.30.-h Diffusion in solids
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance

Improved stoichiometry and misfit control in perovskite thin film formation at a critical fluence by pulsed laser deposition

T. Ohnishi, M. Lippmaa, T. Yamamoto, S. Meguro, and H. Koinuma

Appl. Phys. Lett. 87, 241919 (2005); http://dx.doi.org/10.1063/1.2146069 (3 pages) | Cited 45 times

Online Publication Date: 8 December 2005

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Pulsed laser deposition (PLD) is a good method for growing high-quality functional oxide thin films because of the technical simplicity and the ease with which deposition can be switched from one material to another. However, the repeatability of film quality is often hard to achieve, especially when using several different PLD systems. Here we report the steps that we have taken to grow nearly bulk-equivalent defect-free thin films, with SrTiO3 as an example, by using PLD in a reproducible fashion. The ablation laser fluence was found to have a very strong effect on the lattice constant and defect structure of the films. Nonstoichiometric transfer of material from the ablation target was observed when either the laser fluence or the beam spot area was inadequate.
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81.15.Fg Pulsed laser ablation deposition
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
68.60.-p Physical properties of thin films, nonelectronic

Sr vacancy segregation by heat treatment at SrTiO3 grain boundary

Teruyasu Mizoguchi, Yukio Sato, James P. Buban, Katsuyuki Matsunaga, Takahisa Yamamoto, and Yuichi Ikuhara

Appl. Phys. Lett. 87, 241920 (2005); http://dx.doi.org/10.1063/1.2146051 (3 pages) | Cited 19 times

Online Publication Date: 9 December 2005

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Electron energy loss near-edge structures (ELNES) and first-principles band structure calculations were combined in order to identify native defects which are segregated by heat treatments at the vicinity of SrTiO3 grain boundary (GB). Spectral differences between the bulk and the vicinity of GB mainly appear around the second peak of O K ELNES. The spectral differences can be reproduced by calculating the theoretical O K ELNES from the first-nearest-neighbor oxygen to a Sr vacancy. It is therefore concluded that the Sr vacancies are concentrated in the vicinity of GB by the heat treatment.
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61.72.J- Point defects and defect clusters
64.75.-g Phase equilibria
61.72.Mm Grain and twin boundaries
79.20.Uv Electron energy loss spectroscopy
81.40.Gh Other heat and thermomechanical treatments

Bulk crystals of tetracene grown by the vapor-Bridgman technique

J. Niemax and J. Pflaum

Appl. Phys. Lett. 87, 241921 (2005); http://dx.doi.org/10.1063/1.2146072 (3 pages) | Cited 3 times

Online Publication Date: 9 December 2005

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A universal approach is described for preparing single crystals of organic materials that can only be sublimed, in this case tetracene, with extensions of several millimeters along all three dimensions. It is observed that crystals grown by this technique are more brittle than crystals grown by conventional sublimation methods. The mechanical properties are found to be governed by cracks oriented along (001) basal planes. By Laue diffraction it is revealed that the crystal is composed of subgrains. These grains are separated by small angle tilt boundaries that cause visible traces along the [100] direction on (001) fracture planes. The crack formation during growth is explained to result from tilt boundaries terminating within the crystal.
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81.10.Fq Growth from melts; zone melting and refining
81.10.Bk Growth from vapor
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.Mm Grain and twin boundaries

Texture of NiGe on Ge(001) and its evolution with formation temperature

B. Balakrisnan, C. C. Tan, S. L. Liew, P. C. Lim, G. K. L. Goh, Y. L. Foo, and D. Z. Chi

Appl. Phys. Lett. 87, 241922 (2005); http://dx.doi.org/10.1063/1.2135210 (3 pages) | Cited 11 times

Online Publication Date: 9 December 2005

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Texture of NiGe on Ge(001) and its evolution with formation temperature have been investigated. Pole figure investigation showed that NiGe formed by rapid thermal annealing of Ni(35 nm)/Ge(001) largely consists of epitaxial grains with orientation relationships: NiGe(111)[0math1]//Ge(001)[110],NiGe(020)[001]//Ge(001)[100], NiGe(201)[10math]//Ge(001)[110], NiGe(211)[01math]//Ge(001)[110],NiGe(112)[20math]//Ge(001)[110], and NiGe(210)[001]//Ge(001)[100]. For NiGe formed at 400 °C, NiGe(111)[0math1]//Ge(001)[110],NiGe(020)[001]//Ge(001)[100],NiGe(201)[10math]//Ge(001)[110], and NiGe(211)[01math]//Ge(001)[110] were found to be the preferred orientations, while NiGe formed at 600 °C was dominated by NiGe grains with NiGe(111)[0math1]//Ge(001)[110] orientation. The increasing dominance of the grains with NiGe(111)[0math1]//Ge(001)[110] orientation is attributed to the minimum lattice mismatch with this orientation.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
68.47.De Metallic surfaces
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