Slanted Columns Research Articles

The effect of thickness and deposition angle on structural, chemical and magnetic properties of nickel slanted columns

In this work, the influence of different deposition angles on the structural, chemical and magnetic properties of nickel (Ni) thin films was investigated. Nickel samples were deposited by glancing angle deposition technique at two different angles, 65o and 85o. Characterization of the thin films was carried out by scanning electron microscopy, X-ray photoelectron spectroscopy and magneto-optical Kerr effect microscopy. Structural analysis was found that the changes in the deposition angle have a great influence on the porosity of the film as well as on the amount of the present nickel oxide (NiO) in the samples. On the other hand, we have also found that different deposition angle changes the magnetic response of nickel film. The coercivity of the samples deposited at the angle of 85o is significantly higher compared to the samples deposited at lower angle which could be correlated with the higher porosity and the amount of NiO in the thin films.

Structure and properties of the low-energy deposited TiO2 thin films: results of the molecular dynamics simulation

The classical molecular dynamics simulation of the low-energy glancing angle deposition of titanium dioxide films is performed. The deposition angle varies from 60° to 80°. It is found that the film structure consists of parallel slanted columns which lead to the anisotropy of films properties. The difference between the main components of the refractive index tensor is about 0.14, which is close to the values obtained for high-energy titanium dioxide films and larger than 0.03 obtained earlier for silicon dioxide films.

Anisotropy of glancing angle deposited films: results of atomistic simulation

Anisotropy of SiO2 films fabricated by glancing angle deposition is investigated using the classical atomistic simulation and anisotropic Bruggeman effective medium theory. The voids between the slanted columns, occurring as a result of glancing angle deposition, are considered as ellipsoids. Averaged shape parameters of these ellipsoids are defined using the density gradient tensor. Calculated values of difference of refractive index components of glancing angle deposited SiO2 films are in accordance with experiment.

Tailoring angular selectivity in SiO2 slanted columnar thin films using atomic layer deposition of titanium nitride

Core-shell slanted nanocolumnar thin films (SCTFs) were produced by e-beam glancing angle deposition of SiO2 and subsequent atomic layer deposition (ALD) of TiN. Conformity of the ALD film over the slanted columns was confirmed by transmission electron microscopy and energy dispersive X-ray spectroscopy mappings. Angle resolved spectrophotometry characterization revealed angle-dependent transmission of the films, akin to their fully metallic counterparts. We found that such inclined core-shell nanocolumn films enable tailoring of the angular selectivity independently from the SCTF thickness and density.

Atomistic simulation of the glancing angle deposition of SiO2 thin films

The classical molecular dynamics simulation of the glancing angle deposition of silicon dioxide films with practically meaningful dimensions is performed. The formation of separated slanted columnar structures is investigated for different deposition angles and different energies of sputtered silicon atoms. It is shown that a decrease in the angle between the flux of deposited atoms and the normal to the substrate leads to the decrease of column thicknesses and distances between the columns. The high-energy deposition with small deposition angles results in the formation of dense films without separate columnar structures. The increase of substrate temperature leads to partial merging of nearby columns. The glancing angle deposition with low energies of sputtered silicon atoms results in the growth of disordered columns with different dimensions, shapes, and tilt angles. Annealing of high-energy glancing angle deposited films results in partial merging of slanted columns. The obtained simulation results are in a good agreement with existing experimental data.

Bubble Behavior in Marine Applications of Bubble Columns: Case of Ellipsoidal Bubbles in Slanted and Rolling Columns

Using a hexapod ship motion emulator, the influence of floating vessel motion on the trajectory and velocity profile of single ellipsoidal bubbles is investigated from the images provided by a high-speed camera. Varying the amplitude and frequency of the vessel motion, relations between the column motion and variations in the bubbles’ trajectories are analyzed. Spectral analysis by means of fast Fourier transforms helps demarcate the factors influencing the bubbles’ zigzag flow patterns, in terms of contributions stemming from column wall effects, column oscillation frequency, and column angle of inclination. Although the column rolling motion is shown to have little effect on the rising velocity of the bubbles, its incidence on shaping the bubbles’ number density distribution and bubble flow patterns is remarkable, suggesting that these factors have to be accounted for in the marine context of floating vessels.

Simulation of Soil Water and Salt Transport with Sand Column in Coastal Saline Soil Based on COMSOL

In the paper, transport of water and Cl- under leaching was 2D-digitally simulated with COMSOL Multi-physics. In a two-dimensional transient cross-sectional model. COSMOL was used to investigate water and solute transport in the soil column coupled with variable sand column forms, with “a” denoting no sand column, “b” with one vertical middle sand column, “c “ with one long Slanted sand column, “d” with two long Slanted X-shaped sand columns. The parameters of the model were primarily based on the soil physical properties measured at coastal clay loam saline soil in Tianjin. The simulation results showed that, given same initial and same boundary conditions, sand column increased the transport efficiency of water and salt, which depends on the position and angle of sand column accordingly. The slanted columns were overall superior to the vertical ones in transport efficiency. In sum, “d” was the best type, “c” was the second best and “b” was the third, according to the efficiency of salt leaching and the efficiency of the utilization of water resources.

Kondorski reversal in magnetic nanowires

Magnetization reversal in nanowire systems, such as alnico-type permanent magnets, slanted columns produced by glancing-angle deposition, and nanowires embedded in alumina templates, is investigated by model calculations. The angular dependence of the domain-wall propagation is Kondorski-like, reminiscent of Kondorski pinning in bulk materials but with a somewhat different physics and consistent with Kerr hysteresis-loop measurements. Criss-cross patterning of alnicos improves the coercivity but reduces the remanence, with virtually zero net effect on energy product. Finally, we briefly discuss the wire-radius dependence of the coercivity in the context of "shape anisotropy" and the occurrence of interaction domains in alnico.

Adherence of human mesenchymal stem cells on Ti and TiO2 nano-columnar surfaces fabricated by glancing angle sputter deposition

The interaction of human mesenchymal stem cells (hMSCs) with Ti and TiO2 nano-columnar surfaces fabricated using glancing angle sputter deposition was investigated. The adherence and proliferation of hMSCs on different nano-columnar surfaces, including vertical columns, slanted columns and chevrons, were examined with calcein-acetoxymethyl ester fluorescence staining and scanning electron microscopy. For comparison, adherence of hMSCs on compact, dense films was also studied. After 24h and 7 days, adherent and viable cells were observed on both, Ti nano-columns as well as dense Ti films, which confirms the biocompatibility of these nanostructures. Very small pseudopodia with width of approximately 20–35nm and length varying from 20 to 200nm were observed between the nano-columns, independent of the type of the nano-columnar morphology. Large inter-column spacing and effectively increased surface area make these nanostructures promising candidates for bio-functionalization or drug loading on the surface of Ti-based implants.

Optical properties and microstructure of Ta2O5 thin films prepared by oblique angle deposition

Tantalum pentoxide thin films are prepared by oblique angle electron beam evaporation. The influence of flux angle on the surface morphology and microstructure is investigated by scanning electron microscopy (SEM). The Ta2O5 thin films are anisotropic with highly orientated nanostructure of slanted columns. The porous microstructure of the as-deposited films results in the decrease of effective refractive index and packing density with increasing deposition angle. The anisotropic structure results in optical birefringence. The in-plane birefringence increases with the increase of deposition angle and reaches the maximum of 0.055 at the deposition angle of 70. Anisotropic microstructure and critical packing density are the two key factors to influence the in-plane birefringence.

Ion Beam Assisted Square Spiral Photonic Crystal Fabrication

AbstractPhotonic crystals currently hold exciting potential in waveguiding applications with the ability to greatly reduce waveguide bend radii, allowing for the realization of photonic networks with increased complexity and device density. Square spiral photonic crystals are comprised of periodic arrays of slanted cylindrical columns with periodic abrupt 90° changes in the column growth direction. The abrupt changes produce elbows which correspond to points in the three-dimensional diamond lattice, which are commonly referred to as diamond:n photonic crystal structures based on the nth nearest neighbor lattice point between column arms. The diamond:n structures are characterized by four parameters: column separation, spiral pitch, column diameter, and column growth angle. These structures have been shown theoretically to have a three-dimensional relative bandgap of approximately 15% for a direct silicon diamond:1 structure and approximately 24% for an inverse silicon diamond:5 structure with circular column cross sections. Silicon square spiral photonic crystals can be grown by a single-step thin film deposition process known as glancing angle deposition (GLAD), which utilizes rotation of lithographically patterned substrates and advanced control algorithms. While using GLAD to grow square spiral photonic crystals in a single-step process is desirable, it does have inherent limitations. Physical vapor deposited films deposited at oblique incidence angles form columns with angle ≤ 60° relative to the substrate normal. This deviates from the optimal diamond:1 and diamond:5 structures which require film growth angles of approximately 64° and 74°, respectively. Here we present SEM images of periodic silicon square spiral films grown with a vapor source incidence angle of 85° that indicate an average column tilt angle of 57˚ for films grown with the basic GLAD process and an average column tilt angle between 61˚ and 65˚ using an ion-assisted GLAD process. Photonic simulations indicating that square spiral films with complete three-dimensional photonic bandgaps are only achievable via ion-assisted GLAD are also presented.

Preparation and characterization of nanostructured ZrO 2 thin films by glancing angle deposition

ZrO 2 films were prepared by electron beam evaporation with glancing angle deposition (GLAD) technique. The as-deposition and annealed ZrO 2 films are all amorphous, different from that deposited at normal incidence. Due to the shadowing effect, a highly orientated structure composed of slanted columns formed, and the obtained films became the mixture of slanted columns and voids. The relationship among the effective refractive index, packing density and flux incident angle was investigated. The refractive index and packing density of ZrO 2 films decrease with the increase of the incident angle. The in-plane birefringence of GLAD ZrO 2 films was calculated. At the packing density of 0.576, the maximum birefringence is 0.037.

Structural and optical properties of nanostructured TiO 2 thin films fabricated by glancing angle deposition

TiO 2 films deposited by electron beam evaporation with glancing angle deposition (GLAD) technique were reported. The influence of flux angle on the surface morphology and the microstructure was investigated by scanning electron microscopy. The GLAD TiO 2 films are anisotropy with highly orientated nanostructure of the slanted columns. With the increase of flux angle, refractive index and packing density decrease. This is caused by the shadowing effect dominating film growth. The anisotropic structure of TiO 2 films results in optical birefringence, which reaches its maximum at the flux angle α = 65°. The maximum birefringence of GLAD TiO 2 films is higher than that of common bulk materials. It is suggested that glancing angle deposition may offer an effective method to obtain tailorable refractive index and birefringence in a large continuous range.

Morphology of periodic nanostructures for photonic crystals grown by glancing angle deposition

An enhancement of the glancing angle deposition (GLAD) technique called PhiSweep was used to grow slanted columns of silicon and titanium dioxide onto patterned substrates. The PhiSweep technique involves periodically rotating the substrate back and forth during the deposition process, which reduces column fanning caused by anisotropy in the shadowing conditions. The patterned substrates consisted of a tetragonal array of hillocks with 100, 200, and 300 nm periodicities and were fabricated using electron beam lithography. The PhiSweep method alters the tilt angle of the slanted columns compared with those grown using traditional GLAD. We present a derivation of the tilt angle of the slanted columns as a function of the parameters of the PhiSweep technique. The tilt angles of the silicon and titanium dioxide films were measured and agree with the predicted values. The films fabricated using the PhiSweep method are compared with similar films grown using traditional GLAD. The PhiSweep technique produced films with substantially less column fanning than those grown by traditional GLAD. This reduction in column fanning has extended the size range over which periodic GLAD structures, such as square spiral photonic crystals, can be grown.

5,6-Dichloro-1-propylbenzimidazole

The title compound, C10H10Cl2N2, forms centrosymmetric head-to-tail face-to-face dimers with the n-propyl groups exo to the di­chloro­benz­imidazole groups, which are effectively planar. Within a dimer, the least-squares planes are neces­sarily parallel and exhibit an interplanar spacing of 3.412 (2) A, which lies near the short end of the range (3.3–3.8 A) generally accepted to indicate π–π interactions. When viewed normal to the (100) planes, the structure appears as slanted columns of dimers arranged so as to form alternating –aromatic–aliphatic– layers parallel to the (001) planes.

Characterization By Variable Angle Spectroscopic Ellipsometry Of Dielectric Columnar Thin Films Produced By Glancing Angle Deposition

ABSTRACTThin films composed of MgF2 and TiO2 were grown by glancing flux incidence, where the physical vapor flux arrives at the substrate between 80° and 90° with respect to substrate normal. The resulting films are composed of slanted columns inclined toward the incoming flux. The films were modeled using the Bruggemann effective medium approximation (EMA) and were found to be biaxial with one of the principal indices of refraction along the direction of the posts. The indices of refraction for MgF2 and TiO2 films were found to be in the range of 1.06 to 1.2 and 1.36 to 1.62, respectively, at a wavelength of 600 nm. The indices of refraction were found to decrease as the deposition angle increased. The film density was also found to be independent of the film thickness for films ranging in thickness from 500 nm to 3400 nm.

DC and AC self-magnetic field profiles of (6+1) filamentary BSCCO tapes with different filament arrangements measured by Hall probe magnetometry

The magnetic field distribution in the vicinity of (BiPb) 2Sr 2Ca 2Cu 3O 10+ x tapes carrying a transport current was measured with AC/DC Hall probe scanning magnetometer. Magnetic field profiles of multifilamentary BSCCO tapes supplied by DC transport current were compared with those of tapes supplied by AC transport current at frequency 90 Hz. The samples had seven untwisted filaments arranged in columns, in slanted columns or evenly distributed across the tape cross-section. Areas of filamentary regions and the aspect ratios of the samples were nearly identical. We compared calculated magnetic field profiles of each geometry in the regime of full penetration with the measured ones. It was found that in the case of evenly distributed filaments the shapes of DC and AC profiles were very similar, however the tapes with filaments stacked in columns and in slanted columns had very different shapes of DC and AC profiles at the same current amplitudes, especially in low current region. This effect can be attributed to the differences in static and dynamic penetration of flux into the interior of multifilamentary structure of the conductor.

Microchannel Surface Area Enhancement Using Porous Thin Films

Microchannels having highly enhanced surface area have been fabricated by a thin‐film deposition technique known as glancing angle deposition. Porosimetry and simulation of the microstructures was used to estimate the surface area enhancement of the new microchannels. Two distinct types of microchannels have been created. In the first, a pre‐existing microchannel is coated with a film of deposited at a highly oblique angle. The resulting structure consists of the original channel filled with slanted columns of . An example of this type of channel was estimated by porosimetry to have surface area of . The second microchannel type is produced by lithographic methods and consists of films of with helical microstructure bounded by walls of photoresist. Simulation of one example of this type of channel led to an estimate of . This estimate, however, ignores the mesoscopic scale surface roughness of the microstructures. © 2000 The Electrochemical Society. All rights reserved.

Transport ac losses in (Bi,Pb)SrCaCuO-2223/Ag multifilamentary tapes with different filament arrangements

Transport ac losses in multifilamentary (Bi,Pb)SrCaCuO-2223/Ag tapes with different filament arrangements have been measured. The samples were untwisted and had seven filaments, which were arranged in columns, in slanted columns, or evenly distributed across the tape cross-section. The aspect ratio of the samples as well as their filamentary regions was the same. Special care during processing ensured that the filaments had the same orientation or arrangement along the sample length and that filament bridging was avoided. The ac losses were measured in the frequency range 40 Hz–120 Hz. Two different methods of determining the critical current were used: from dc current–voltage characteristics and from the saturation value of ac losses. The experimental results were compared with theoretical models. The normalized ac losses approximately follow the theoretical dependence of a tape with rectangular cross-section of similar aspect-ratio. It was found that the sample with filaments stacked in columns had slightly lower normalized losses at low normalized currents ( I o/ I c<0.2) compared with other filament arrangements. There was no difference in the loss data for the three different filament geometries in the range I o/ I c>0.2. It was also observed that tapes containing bridged filaments, but having similar critical currents, had variable normalized ac loss.

Buckling of Slanted Columns

A slanted column may represent an inclined member of a truss, a frame, or a meridional element of an axisymmetrically deformable conical shell with rigid edges. Such a structure has a unique constraint condition. A set of nonlinear equations for buckling of elastic slanted columns is derived by the variational method in cooperation with the Lagrange multiplier to deal with the constraint condition. The bifurcation of such columns with simply supported ends is considered along with results obtained from conventional methods. No bifurcation will occur for columns with other end conditions. A set of formulas derived from the linearized eigenvalue method is also presented. The results obtained from the latter are slightly higher than those obtained from the nonlinear theory. The buckling loads may lower further if the change of the inclined angle at the loaded end is taken into consideration during the deformations.