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17 Jul 2000

Volume 77, Issue 3, pp. 313-459

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Electric field-induced layer deformations in the subphases of an antiferroelectric liquid crystal device

L. S. Matkin, H. F. Gleeson, L. J. Baylis, S. J. Watson, N. Bowring, A. Seed, M. Hird, and J. W. Goodby

Appl. Phys. Lett. 77, 340 (2000); http://dx.doi.org/10.1063/1.126970 (3 pages) | Cited 20 times

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The layer structure in the antiferroelectric, ferrielectric, and ferroelectric phases of a liquid crystal device is reported, together with its electric field-induced deformation. The field-free chevron angle is comparable to the steric tilt angle, but differs significantly from the optical tilt angle. A sharp field threshold is observed for the chevron to bookshelf transition in the antiferroelectric phase at 1.3 V/μm, while layer deformations occur at much lower fields (0.3 V/μm) in the other subphases. Models are proposed for the layer deformations. © 2000 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
42.79.Kr Display devices, liquid-crystal devices
64.70.M- Transitions in liquid crystals

Molecular-dynamics study of the mechanism and kinetics of void growth in ductile metallic thin films

M. Rauf Gungor, Dimitrios Maroudas, and Shujia Zhou

Appl. Phys. Lett. 77, 343 (2000); http://dx.doi.org/10.1063/1.126971 (3 pages) | Cited 12 times

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A molecular-dynamics study is presented of the mechanism and kinetics of void growth and morphological evolution in ductile metallic thin films subject to biaxial tensile strains. The void becomes faceted, grows, and relieves strain by emission from its surface of pairs of screw dislocations with opposite Burgers vectors. Repeated dislocation generation and propagation leads to formation of a step pattern on the film’s surfaces. A simple phenomenological kinetic model of void growth is derived. Such kinetic equations can be used to formulate constitutive theories of plastic deformation for continuum-scale modeling of void evolution. © 2000 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Qq Microscopic defects (voids, inclusions, etc.)
85.40.Ls Metallization, contacts, interconnects; device isolation
68.60.Bs Mechanical and acoustical properties
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
62.20.F- Deformation and plasticity
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Yx Interaction between different crystal defects; gettering effect
68.35.B- Structure of clean surfaces (and surface reconstruction)

Phonon deformation potentials of α-GaN and -AlN: An ab initio calculation

J.-M. Wagner and F. Bechstedt

Appl. Phys. Lett. 77, 346 (2000); http://dx.doi.org/10.1063/1.127009 (3 pages) | Cited 70 times

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First-principles density functional theory calculations of the deformation potentials are presented for zone-center phonons in GaN and AlN in the wurtzite structure. Three cases of deformations are considered: biaxial and uniaxial strain along the c axis as well as hydrostatic compression. For the resulting atomic structures the phonon frequencies are determined. The combination of calculations for these deformations allows the derivation of elastic constants and phonon deformation potentials. Good agreement is observed with measured values for GaN. No published values for AlN are available. © 2000 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
62.20.D- Elasticity
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Structural evolution of ZnO/sapphire(001) heteroepitaxy studied by real time synchrotron x-ray scattering

Sang Il Park, Tae Sik Cho, Seok Joo Doh, Jong Lam Lee, and Jung Ho Je

Appl. Phys. Lett. 77, 349 (2000); http://dx.doi.org/10.1063/1.126972 (3 pages) | Cited 16 times

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The structural evolution during heteroepitaxial growth of ZnO/sapphire(001) by radio-frequency magnetron sputtering has been studied using real-time synchrotron x-ray scattering. The two-dimensional (2D) ZnO(002) layers grown in the initial stage are highly strained and well aligned to the substrate having a mosaic distribution of 0.01° full width at half maximum (FWHM), in sharp contrast to the reported transition 2D layers grown by molecular-beam epitaxy. With increasing film thickness, the lattice strain is relieved and the poorly aligned (1.25° FWHM) three-dimensional (3D) islands are nucleated on the 2D layers. We attribute the 2D–3D transition to the release of the strain energy stored in the film due to the film/substrate lattice mismatch. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
61.05.cf X-ray scattering (including small-angle scattering)
81.05.Dz II-VI semiconductors
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Use of scanned laser annealing to control the bamboo grain length of Cu interconnects

C. S. Hau-Riege and C. V. Thompson

Appl. Phys. Lett. 77, 352 (2000); http://dx.doi.org/10.1063/1.126973 (3 pages) | Cited 3 times

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Microstructural evolution induced by scanned laser annealing (SLA) of Cu interconnects was found to produce unique large-grained “bamboo” grain structures, with bamboo grain lengths up to ten times the linewidth. These bamboo grain lengths are shown to depend on the scan rate and laser power. By comparing results from experiments on different structures with grain growth simulations, the bamboo grain length induced by SLA is shown to be a strong function of the thermal profile, where steeper thermal profiles yield longer bamboo grains. © 2000 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
61.72.Cc Kinetics of defect formation and annealing
68.55.-a Thin film structure and morphology

Two-photon absorption in GaN, GaInN, and GaAlN alloys

Srinivasan Krishnamurthy, Karen Nashold, and A. Sher

Appl. Phys. Lett. 77, 355 (2000); http://dx.doi.org/10.1063/1.126974 (3 pages) | Cited 10 times

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We have carried out full band-structure-based studies of two-photon absorption coefficients in the GaN compound, and GaInN and GaAlN alloys. An accurate Hamiltonian and resulting wave functions and band structures are used in the calculations. The coefficients in GaN calculated without any adjustable parameters agree very well with recent experiments. We further show that the two-photon absorption coefficients can be increased or decreased by adding In or Al to the GaN compound. The spectral variation of the absorption coefficient can be explained in terms of the alloy-induced changes in the band gap and joint density of states. © 2000 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr Semiconductor compounds

Interdiffusion in NiFe/Cu/NiFe trilayers: Possible failure mechanism for magnetoelectronic devices

W. Brückner, S. Baunack, M. Hecker, J.-I. Mönch, L. van Loyen, and C. M. Schneider

Appl. Phys. Lett. 77, 358 (2000); http://dx.doi.org/10.1063/1.126975 (3 pages) | Cited 10 times

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The evolution of electrical resistance, stress, and microstructure during annealing has been studied on 100 nm NiFe(20 wt %)/200 nm Cu/100 nm NiFe trilayers. Irreversible resistance changes and the concentration-depth profiles show that, at and above 200 °C, diffusion of Ni into Cu as well as of Cu into NiFe occurs. The interdiffusion is held for an important failure mechanism of Cu/NiFe-based magnetoelectronic system at elevated temperatures. © 2000 American Institute of Physics.  
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68.35.Fx Diffusion; interface formation
75.47.De Giant magnetoresistance
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.At Metal and metallic alloys
66.30.Ny Chemical interdiffusion; diffusion barriers
75.50.Bb Fe and its alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Measurement of nanohardness and nanoelasticity of thin gold films with scanning force microscope

B. Kracke and B. Damaschke

Appl. Phys. Lett. 77, 361 (2000); http://dx.doi.org/10.1063/1.126976 (3 pages) | Cited 22 times

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With a scanning force microscope operating in ultrahigh vacuum, we measured local mechanical properties of single crystalline gold islands. The elastic moduli of the gold islands and the substrates sapphire, mica, and quartz were evaluated from force-distance curves. The value of Young’s elastic modulus in [111] direction of the gold grains is (50±16) GPa and was found to be significantly smaller than the bulk modulus of gold. With an indentation technique, the nanohardness of gold islands was investigated. The nanohardness is smaller than the bulk value and depends on the indentation area. This can be interpreted as nanohardening by dislocation interaction in very pure single crystals. © 2000 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
62.20.D- Elasticity
68.35.Gy Mechanical properties; surface strains
62.20.Qp Friction, tribology, and hardness

Synthesis and properties of epitaxial thin films of c-axis oriented metastable four-layered hexagonal BaRuO3

M. K. Lee, C. B. Eom, W. Tian, X. Q. Pan, M. C. Smoak, F. Tsui, and J. J. Krajewski

Appl. Phys. Lett. 77, 364 (2000); http://dx.doi.org/10.1063/1.126977 (3 pages) | Cited 12 times

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We have grown epitaxial thin films of c-axis oriented metastable four-layered hexagonal BaRuO3 on a (111) SrTiO3 substrate by 90° off-axis sputtering techniques. X-ray diffraction and transmission electron microscopy reveal that the films are single domains of c-axis four-layered hexagonal structures with an in-plane epitaxial arrangement of BaRuO3 [2mathmath0]∥SrTiO3[110]. Surfaces with smooth terraces having a step height of a half unit cell (∼4.7 Å) have been observed by scanning tunneling microscopy. The in-plane electrical resistivity of the films is metallic, with a room temperature value of 810 μΩ cm and slightly curved temperature dependence. Their magnetic susceptibility is Pauli paramagnetic. The metastable layered metallic oxide can be used for understanding new solid-state phenomena and device applications. © 2000 American Institute of Physics.
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81.15.Cd Deposition by sputtering
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.61.At Metal and metallic alloys
75.70.Ak Magnetic properties of monolayers and thin films
75.20.Ck Nonmetals
68.35.B- Structure of clean surfaces (and surface reconstruction)

Independent determination of Ge content in thin Si1−xGex quantum wells by spectroscopic ellipsometry

M. Broschwitz, K. Dettmer, and J. Schoenes

Appl. Phys. Lett. 77, 367 (2000); http://dx.doi.org/10.1063/1.126978 (3 pages) | Cited 2 times

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The pseudodielectric functions of Si1−xGex multi-quantum-well samples have been measured by spectroscopic ellipsometry in the photon energy range from 1.1 to 4.5 eV at room temperature. A sharp structure near 3.2 eV, obtained in all our spectra, is identified as an interband transition of the Si1−xGex well, whose exact energy depends on x. By fitting line shapes to the second derivative of the spectra it is possible to determine the Ge content x of the thin Si1−xGex wells. The detailed analysis of the transition energies in comparison with x-ray diffraction data then allows the exact determination of the thicknesses of barriers and wells. The theoretically calculated shift of the transition energies caused by the strain of the Si1−xGex wells was taken into account in our analysis. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Hd Other semiconductors
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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