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4 Nov 2002

Volume 81, Issue 19, pp. 3519-3685

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How to affect stacking fault energy and structure by atom relaxation

J. Cai, C. Lu, P. H. Yap, and Y. Y. Wang

Appl. Phys. Lett. 81, 3543 (2002); http://dx.doi.org/10.1063/1.1519106 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2002

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By a simulated annealing method with a parameterized tight-binding potential, the properties of structure and energy of a generalized stacking fault are investigated. It is shown that for metal Pd, the second-layer spacing from the stacking fault plane expands initially and then contracts with the variation of the stacking fault variable from 0 to 1. The effect of atom relaxation on stacking fault energy is shown to be small. For another metal Pt, the second-layer spacing contracts and the effect of atom relaxation on the stacking fault energy is found to be obvious. In addition, the calculated stacking fault energy is in agreement with experimental results for the two metals. © 2002 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects

Effect of high-density plasma etching on the optical properties and surface stoichiometry of ZnO

K. Ip, K. H. Baik, M. E. Overberg, E. S. Lambers, Y. W. Heo, D. P. Norton, S. J. Pearton, F. Ren, and J. M. Zavada

Appl. Phys. Lett. 81, 3546 (2002); http://dx.doi.org/10.1063/1.1519095 (3 pages) | Cited 26 times

Online Publication Date: 28 October 2002

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Bulk, single-crystal ZnO was etched in Cl2/Ar and CH4/H2/Ar inductively coupled plasmas as a function of ion impact energy. For CH4/H2/Ar, the etch rate (R) increases with ion energy (E) as predicted from a model of ion enhanced sputtering by a collision–cascade process, R∝(E0.5−ETH0.5), where the threshold energy, ETH, is ∼ 96 eV. Band edge photoluminescence intensity decreases with incident ion energy in both chemistries, with a 70% decrease even for low energies ( ∼ 116 eV). Surface roughness is also a function of ion energy with a minimum at ∼ 250 eV, where Auger electron spectroscopy shows there is no measurable change in near-surface stoichiometry from that of unetched control samples. © 2002 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
78.55.Cr III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

High epitaxial quality Y2O3 high-κ dielectric on vicinal Si(001) surfaces

G. Apostolopoulos, G. Vellianitis, A. Dimoulas, M. Alexe, R. Scholz, M. Fanciulli, D. T. Dekadjevi, and C. Wiemer

Appl. Phys. Lett. 81, 3549 (2002); http://dx.doi.org/10.1063/1.1519727 (3 pages) | Cited 18 times

Online Publication Date: 28 October 2002

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Thin films of Y2O3 were grown by molecular-beam epitaxy on silicon aiming at material with adequate crystal quality for use as high-κ gate replacements in future transistors. It was found that Y2O3 grows in single-crystalline form on 4° misoriented Si(001), due to an in-plane alignment of 〈110〉Y2O2 to the silicon dimer direction. The Y2O3 layers exhibit a low degree of mosaicity, a small proportion of twinning and sharp interfaces. This represents a significant improvement compared to material grown on exact silicon surfaces. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Influence of the quantum-well shape on the light emission characteristics of InGaN/GaN quantum-well structures and light-emitting diodes

H. W. Shim, R. J. Choi, S. M. Jeong, Le Van Vinh, C.-H. Hong, E.-K. Suh, H. J. Lee, Y.-W. Kim, and Y. G. Hwang

Appl. Phys. Lett. 81, 3552 (2002); http://dx.doi.org/10.1063/1.1519725 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2002

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Structural and optical properties of various shapes of quantum wells (QWs), including rectangular, triangular, trapezoidal, and polygonal ones are investigated. Photoluminescence (PL) measurements show that the highest light emission efficiency and the best reproducibility in the intensity and wavelength are obtained from trapezoidal QWs. The temperature dependence of PL spectra indicates the more localized nature of excitons in the trapezoidal QWs. A plan-view transmission electron microscopy shows that quantum dots (QDs) are formed inside the dislocation loop in trapezoidal QWs. The distribution of QDs in size and composition becomes more uniform with trapezoidal QWs than with rectangular QWs, leading to superior light-emission characteristics. It is suggested that QD engineering and dislocation control are possible, to some extent, by the modulation of the QW shape in InGaN/GaN-based light-emitting devices.© 2002 American Institute of Physics.
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78.67.De Quantum wells
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence

Surface dihydrides on Ge(100): A scanning tunneling microscopy study

Jae Yeol Maeng, Jun Young Lee, Young Eun Cho, Sehun Kim, and Sam K. Jo

Appl. Phys. Lett. 81, 3555 (2002); http://dx.doi.org/10.1063/1.1520329 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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We studied the atomic scale surface evolution of Ge(100) exposed at 300 K to gas-phase hydrogen atoms, H(g). Surface H(g) uptake created a 2×1:H phase, quickly reaching ∼1 monolayer H coverage. However, in contrast to the Si(100) surface, dangling bonds of the Ge(100) surface could never be completely removed by H(g) due to their regeneration by highly efficient surface H abstraction. This, together with the instability of surface dihydrides, GeH2(a), inhibited the large-scale formation of 3×1:H and 1×1:H phases. Short GeH2(a) rows, present in small metastable 3×1:H domains formed near defect sites, were etched selectively by H(g), producing line defects. © 2002 American Institute of Physics.
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68.43.Mn Adsorption kinetics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Control of crystallographic tilt in GaN grown on Si (111) by cantilever epitaxy

T. M. Katona, J. S. Speck, and S. P. DenBaars

Appl. Phys. Lett. 81, 3558 (2002); http://dx.doi.org/10.1063/1.1519943 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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We have eliminated the crystallographic tilt associated with lateral growth during cantilever epitaxy by adjusting the lateral to vertical growth rate during the initial stages of growth. Cantilever epitaxy is a single growth run technique utilizing periodic, parallel mesas formed by etching the substrate. We have studied the relationship between the geometry of the “wing” region, the GaN spanning the etched trench, and the magnitude of crystallographic wing tilt. Cross-sectional scanning electron microscopy was used to characterize the geometry of the wing region, and x-ray diffraction was used to measure the magnitude of crystallographic tilt. It was found that by starting the GaN overgrowth with a slow lateral growth rate, compared to the vertical growth rate, a low tilt (⩽0.2°) was established and stabilized. The lateral growth rate can be increased during later stages of growth to assist in fast coalescence of neighboring stripes without significantly affecting the magnitude of crystallographic tilt. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
61.72.Mm Grain and twin boundaries
81.65.Cf Surface cleaning, etching, patterning

Potential sputtering of proton from hydrogen-terminated Si(100) surfaces induced with slow highly charged ions

K. Kuroki, N. Okabayashi, H. Torii, K. Komaki, and Y. Yamazaki

Appl. Phys. Lett. 81, 3561 (2002); http://dx.doi.org/10.1063/1.1520335 (3 pages) | Cited 12 times

Online Publication Date: 28 October 2002

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A potential sputtering mechanism of hydrogen has been studied for impact of slow highly charged Xeq+ ions (<5 keV, q = 4–12) on well-defined H-terminated Si(100) surfaces. It was found that the sputtering yields of protons are proportional to qγ (γ ∼ 5), independent of the surface condition, that is, for both Si(100)2×1-H surface and Si(100)1×1-H surface. The yield for Si(100)1×1-H surface was ten times larger than that for Si(100)2×1-H surface, although the H coverage of the former is only twice the latter. Surface roughness is found to be the key parameter to vary the yield, and also to influence the energy distribution of sputtered protons. These findings are consistently explained with a pair-wise bond-breaking model induced by a double electron capture, where the classical over barrier process plays an essential role. © 2002 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Atomic and electronic structures of doped grain boundaries in SrTiO3

Hyunju Chang, Youngmin Choi, Jae Do Lee, and Hongsuk Yi

Appl. Phys. Lett. 81, 3564 (2002); http://dx.doi.org/10.1063/1.1519960 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2002

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The atomic and electronic structures of pristine, Mn- and Nb-doped grain boundaries in SrTiO3 are investigated by atomistic simulations and cluster calculations. The atomic structures of (310) symmetric tilt grain boundaries in SrTiO3 are determined by atomistic simulation using empirical potentials. The defect energies of Mn(Nb)-doped models are calculated and discussed in relation to the concentration profiles of Mn(Nb) in SrTiO3 grain boundaries. The local electronic structures near Mn(Nb)-doped grain boundaries in SrTiO3 are determined using embedded cluster calculations based on the density functional theory. The charge density of each system is calculated to elucidate the electronic structure of the grain boundary. The calculation results agree well with previous experimental observations of the atomic structures and grain boundary charges near the Mn(Nb)-doped grain boundary in SrTiO3. © 2002 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
71.55.Ht Other nonmetals
61.72.Bb Theories and models of crystal defects
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Coiling-chirality changes in carbon microcoils obtained by catalyzed pyrolysis of acetylene and its mechanism

Shaoming Yang, Xiuqin Chen, and Seiji Motojima

Appl. Phys. Lett. 81, 3567 (2002); http://dx.doi.org/10.1063/1.1516612 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2002

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As can be seen in the double helix of DNA, the single helix of proteins, etc., the three-dimensional (3D) helical/spiral structure is a fundamental structure of living things, and affords them critical functionalities. Helically coiled carbon fibers, which usually take the peculiar form of either a microcoil or a helix or twisted form, referred to as “carbon microcoils hereafter,” are of great interest due to their novel functionality and various potential applications. They can potentially be used in electromagnetic absorbers and/or filters, 3D composites, smart tunable electrical devices, microsensors, chiral catalysts, etc. © 2002 American Institute of Physics.
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81.05.U- Carbon/carbon-based materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Preferential carbon etching by hydrogen inside hexagonal voids of 6H-SiC(0001)

Dirk Sander, Wulf Wulfhekel, Margrit Hanbücken, Serge Nitsche, Jean Pierre Palmari, Frédéric Dulot, François Arnaud d’Avitaya, and André Leycuras

Appl. Phys. Lett. 81, 3570 (2002); http://dx.doi.org/10.1063/1.1519962 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2002

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6H-SiC(0001) samples have been etched in a hot-wall chemical vapor deposition reactor at a hydrogen pressure of 13 mbar at 1800 °C. The surface morphology and elemental composition have been studied by scanning electron microscopy and micro-Auger analysis. Stoichiometric etching of SiC with equal atomic concentrations of Si and C is found on the flat sections of the surface, but in hexagonal voids of the SiC samples, a selective removal of C, leading to a pure Si surface at the bottom of the voids, is observed. Fast gas diffusion is the main transport mechanism for etching of the flat surface, while Knudsen diffusion becomes important inside the voids. It is proposed that the lower diffusion constant of reaction products containing Si compared to those containing C, leads to a preferential removal of C and a Si enrichment inside the voids. © 2002 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Hd Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
79.20.Fv Electron impact: Auger emission
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