In-plane Relationship Research Articles

Epitaxial SrRuO3 thin films on (001) SrTiO3

Highly conductive metallic oxide thin films of SrRuO3 with single crystalline quality have been grown on (001) SrTiO3 by using pulsed laser deposition. The films have a [00l] orientation with an in-plane relationship of [110]SrRuO3 // [100]SrTiO3. They have excellent metallic behavior with room temperature resistivity of ∼310 μΩ cm and a residual resistance ratio of about 7 at 4.2 K, the largest reported to date. A clear ferromagnetic transition at ∼147 K was detected by resistivity and magnetic measurements. However, the transition becomes blurred as the density-of-point defects increases in the films following a 400 keV proton irradiation with an accumulative dose up to ∼6.0×1016 ions/cm2.

TEM investigation of halide CVD grown Bi 2Sr 2CaCu 2O 8 + x films

The superconducting Bi 2Sr 2CaCu 2O 8+ x (Bi-2212) phase has been deposited by halide CVD on two different substrate materials, MgO(001) and SrTiO 3(001). Metal iodides and oxygen were used as precursors. The films grew with a strong [001] orientation and only the 00 l reflections with l=2 n were observed. The in-plane orientational relationships were determined by TEM to be [100] MgO//[100] Bi-2212 and [100] MgO//[110] Bi-2212 for the MgO(001) substrate and [100] SrTiO3//[110] Bi-2212 for the SrTiO 3(001) substrate. The interfacial regions of the two substrate materials were investigated by cross sectional HREM, revealing that the interface is nearly atomically abrupt for both substrate materials. The first atomic layer of the films were found to be a BiO layer.

Substrate dependence in the growth of epitaxial Pb1−xLaxTiO3 thin films

The metalorganic chemical vapor deposition (MOCVD) technique has been applied to the growth of epitaxial Pb1−xLaxTiO3 (PLT) thin films with x=0.28. By first introducing an initial TiO2 layer, three-dimensional epitaxial PLT films were grown on the (100) surface of MgO substrate. For both KTaO3 (100) and Al2O3 (0001) substrates, heteroepitaxy was achieved without the introduction of TiO2 as the initial, intervening layer between the PLT film and the substrate. On Al2O3 substrates, PLT films with a [111] preferred orientation were grown with a good epitaxial in-plane relationship.

Comparison of the Microstructure of AlN Films Grown by MOCVD and by PLD on Sapphire Substrates

ABSTRACT(0001) aluminium nitride thin films were grown epitaxially on (0001) Sapphire substrates by MOCVD at 1200° C and PLD at 800° C. Both films have the same epitaxial growth relationship: (0001)AlN//(0001)Sap, and the same in-plane relationship which shows a 30° rotation between A1N and Sapphire: [ 12 10]AlN//[0 110]Sap and [10 10]AlN //[ 2110]Sap. The full width at half maximum (FWHM) of x-ray rocking curve of the MOCVD A1N film was 0.16° and PLD A1N film was 0.2°. Films grown by both MOCVD and PLD showed high crystalline quality. HRTEM images showed that these films are single crystalline with very low density of defects.Dislocations in the film parallel to the film / substrate interface were observed in both A1N films. Atomic force microscopy images showed that the MOCVD films have flatter and larger terraces than the PLD films. The PLD technique for A1N growth needs to be improved further. But both films have a surface roughness of approximately 100nm.

Halide chemical vapour deposition of Bi 2Sr 2CaCu 2O 8+ x: aspects of epitaxy

The superconducting Bi 2Sr 2CaCu 2O 8+ x phase has been deposited by halide chemical vapour deposition (CVD) on three different substrate materials, MgO(001), SrTiO 3(001) and LaAlO 3(001). Metal iodides and oxygen were used as precursors. The films were found to grow with a strong [001] orientation and only the 00 l reflections with l = 2 n were observed, with rocking curve fwhm values of about 0.3° in θ. The in-plane orientational relationships were determined by ϕ-scans for all three substrate materials. These relationships were found to be [100] MgO |[100] Bi-2212 for the MgO(001) substrate and [100] Substrate |[110] Bi-2212 for the SrTiO 3(001) and LaAlO 3(001) substrates. The results are in good agreement with other determinations of the in-plane orientational relationships.

Epitaxial Aluminum‐Doped Zinc Oxide Thin Films on Sapphire: I, Effect of Substrate Orientation

Epitaxial thin films of Al‐doped zinc oxide have been grown on sapphire substrates by pulsed laser ablation. The effect of substrate temperature, background pressure of oxygen, and substrate orientation (A, M, R, C) on the orientation relationships between ZnO and sapphire have been evaluated using on‐ and off‐axis X‐ray diffractometry. Under all growth conditions zinc oxide, on A‐ and C‐plane sapphire, grew with the c‐axis perpendicular to the substrate. In contrast, on M and R orientations of sapphire, ZnO grew with its c‐axis parallel or perpendicular to the substrate depending on the substrate temperature and background pressure employed during growth. In all cases only one unique in‐plane relationship between the sapphire substrate and the zinc oxide film was found with the exception of the M‐plane at high substrate temperatures.

Nonlinear finite element analysis of composite beams and arches using a large rotation theory

Today's aerospace industry has advanced to the point of using optimum design techniques in virtually all applications. In structural elements, orthotropic fiber composite materials have emerged as lighter, stronger and a more easily manufactured solution to the material application aspect of design. Composites have the distinct advantage of being designed and built to many different desired specifications by varying materials, amount of matrix/fiber and orientation. As with many high performance applications, the analysis techniques of fiber composites are more complicated than for the simpler counterparts. This research has been directed to capturing large cross-sectional rotation incorporating a geometrically nonlinear finite element composite arch model. The model was derived and simplified from a (two-dimensional) 2-D shell theory that has been demonstrated to be accurate for large displacements and only moderate rotations. The current effort uses a similar potential energy based finite element model with through-the-thickness shear. Large rotation kinematics are derived in a vector format which includes a tangent function in the in-plane displacement relationship. Previously published research (Creaghan and Palazotto, 1994; Palazotto and Dennis, 1992) used a small angle approximation to simplify stiffness expressions, limiting those theories to moderate cross-sectional rotation angles. This tangent function is modeled by a series representation of the angle and thereby preserving the existing degrees of freedom. The approach decomposes the Green strain components into convenient forms for inclusion in the potential energy function which is then extended to a nonlinear finite element solution method. The potential energy is simplified by substituting the new rotation function for the previous rotation angle. Riks and displacement control are used to show solutions to several nonlinear arch problems. Other published analytical and experimental results are compared with the current research. This work is a simple extension of a previously published large displacement/moderate rotation theory (Creaghan and Palazotto, 1994), but the results show significant improvement when large cross sectional bending angles are present.

Band lineup and in-plane effective mass of InGaAsP or InGaAlAs on InP strained-layer quantum well

We describe the band lineups of InGaAlAs on (001) InP as well as InGaAsP on (001) InP system with strain effects, based on the Harrison model. We show that the compressive strain does not affect the band position so much, and tensile strain raises the band position in the InGaAsP system. It is also shown that both compressive and tensile strains raise the band positions in the InGaAlAs system. The conduction and valence band positions of InGaAs, InGaAsP, and InGaAlAs relative to InP valence band are given in approximate formulas as a function of the strain. We calculate the energy versus in-plane wave vector relationship of the InGaAsP/InGaAs(P) InGaAlAs/InGa(Al)As on InP strained quantum-well systems. We obtain the in-plane effective mass of the strained quantum-well system by fitting the dispersion relationship to a parabolic curve. The in-plane effective masses of several kinds of strained quantum-well systems are listed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Elastoplastic Nonlinear Analysis of Flexibly Jointed Space Frames

Conventional approaches to the design and analysis of steel frames commonly assume the structure to be of either simple or rigid construction. In the simple construction approach, connections between members are not capable of transmitting moment, whereas in the rigid construction approach, full rotational continuity is provided. In practice, however, most connections are semirigid possessing some degree of rotational stiffness as a function of the applied load. A method for the nonlinear analysis of space frames incorporating the effect of flexible or semirigid joints is presented. A two-node zero length connection element with three rotational degrees of freedom per node is used to model the joint. The connection element may be introduced at one or both ends of a general thin-walled beam-column element, via kinematic transformation and static condensation. The proposed connection element may be represented by any set of nonlinear coupled or uncoupled, in-plane, out-of-plane, and torsional moment-rotation relationships. Several numerical examples are presented, which show that the response of a flexibly jointed frame is very sensitive to joint behavior.