Search

A circular membrane clamped at the periphery is allowed to adhere to or to delaminate from a planar surface of a cylindrical punch in the presence of intersurface forces with finite range and magnitude. Assuming a uniform disjoining pressure within the cohesive zone at the delamination front, the adhesion-delamination mechanics is obtained by a thermodynamic energy balance. Interrelations between the instantaneous applied load, punch displacement, and contact circle, and the resulting critical thresholds of 'pinch-off,' 'pull-off' and 'pull-in' are derived from the first principles. Two limiting cases are obtained: (i) intersurface force with long range and small magnitude in reminiscence of the classical Derjaguin--Muller--Toporov (DMT) model and (ii) short range and large magnitude alluding to the Johnson-Kendall-Roberts (JKR) model. The DMT-JKR transitional behavior has significant impacts on adhesion measurements, microelectromechanical systems, and life-sciences. [DOI: 10.1115/1.3112745] Keywords: thin film adhesion, delamination, surface force, disjoining pressure, cohesive zone

We measured the second harmonic generation response of a thin film consisting of chiral molecules with four wave plates having different retardation coefficients. By means of the fitting procedure described in a previously reported formalism, we demonstrated that a single set of tensor components of second order surface nonlinearities fits all the data. Our results provide clear experimental evidence for the validity of this method, which can find applications in the studies of chiral structures and achiral anisotropic materials. OCIS codes: 160.1585, 190.4160.

The adsorption of ruthenium-dye molecules out of ethanol solution onto TiO2 particles of nanoporous TiO2 films was used to study the molecules' diffusion through these layers by means of optical absorption spectrometry. These diffusion constants for diffusion through the nanoporous network are up to 3 orders of magnitude lower than in bulk ethanol and are discussed with respect to the properties of the nanoporous material.

Monte Carlo simulations of disjoining-pressure isotherms for soluble-surfactant-stabilized free thin films are presented. A disjoining-pressure isotherm is defined such that films of all thicknesses on that isotherm are in equilibrium with the same infinite reservoir of surfactant and solvent.

A new series of mixed phylene-thiophene oligomers with terminal n-hexyl groups is synthesized and characterized both as bulk solids and thin films. The compounds are thermally stable, and the thin films adopt microstructures with lattice spacings suggestive of molecular alignment along the substrate normal.

Using an imaging mode based on the adjustment of a negative value of the spherical-aberration coefficient of the objective lens of a transmission electron microscope, we successfully imaged all types of atomic columns in the dielectric SrTi[O.sub.3] and the superconductor Y[Ba.sub.2][Cu.sub.3][O.sub.7]. In particular, we were able to view the oxygen atoms which, due to their low scattering power, were not previous[y accessible, and this allowed us to detect local nonstoichiometries or the degree of oxygen-vacancy ordering. This technique offers interesting opportunities for research into oxides, minerals, and ceramics. In particular, this holds for the huge group of perovskite-derived electroceramic materials in which the local oxygen content sensitively controls the electronic properties., Thin films of Ba- and Sr-based perovskites have great potential for application, in particular as high-permittivity dielectrics in microelectronics or nonvolatile memory devices. Research on the structure and properties of [...]

The pulsed-laser deposition (PLD) technique is currently used in research laboratories to obtain thin films from a broad range of materials even with a complex composition. The differences in the crystalline properties of ZnO films grown by laser ablation, using either nanosecond or femtosecond pulsed-laser deposition (PLD) is presented.

A piezoelectric elastic fin micromotor was fabricated and studied. It was based on a PbZr(sub0.53)Ti(sub0.47)O(sub3) thin film driving a micromachined silicon membrane. Torque, output power and device efficiency were extracted from measurements of angular velocity and acceleration of the motor. Values of 1020 rpm and 0.94 muNm were seen for the velocity and torque.

Pulsed laser deposition (PLD) is of interest in the deposition of thin films of metal oxides. Ta(sub2)O(sub5) thin films are of interest because of their potential in high density dynamic random access memories. Visible laser ablation has been used to deposit Ta(sub2)O(sub5) thin films with better quality. A study was undertaken to determine if the nature of the 532 nm laser ablation process of Ta(sub2)O(sub5) is thermally or photochemically driven, or a combination of both.

GaN films implanted with Mg and Be ions were studied for optical and structural characteristics. Annealed Mg implanted GaN showed low temperature photoluminescence (PL) spectra of 356 nm near band edge emission, and a 528 nm green band deep level emission. The 528 nm green band emission may be attributed to the Mg implantation induced clustering defect.

Researchers examined the sub band-edge emission bands of AlxGa1-xN films deposited on 6H-SiC(0001) surfaces. Cathodoluminescence revealed the presence of strong band-edge emission at 4.2 K. This is attributable to donor-bound excitons and two deep bands, one being a donor-shallow-acceptor pair emission, and the other being yellow emission bands in the GaN. Both bands had an energy shift with increasing Al mole fraction.

Plasmon surface polaritons and guided optical waves have been used for characterizing interfaces and thin organic films. Examples can show how interfacial light of a sort can be used to look at thin coatings at a solid/liquid or solid/air junction. Thickness determination can be very precise and samples can go from self-assembled monolayers to multilayer samples made with the Langmuir/Blodgett/Kuhn technique or other polyelectrolyte deposition. Kinetic time-dependent processes also can be looked at with the technique. Combination set-ups of surface plasmon optics with electrochemical techniques can allow for online characterization of assorted surface functionalization methods, perhaps for bio sensor or other sensor use. Evanescent wave optics are discussed.

Six orthotropic film Love elastic modes with multiperiodic surface corrugations and their filtering characteristics at 1.813 MHz are investigated. The use of a stop-band filter enables the imposition of amplitude tapers. The pass-band filter which functions as a tuned circuit with very high Q-factor replace piezoelectric crystal in certain devices. The multiple scale method is used to obtain coupled-mode equations.

The effects of the substrates on structural and magnetic properties of Co:TiO2 films are examined. It is observed that the films on Si substrates are rutile and the films on LAO and STO substrates are single phased anatase.

The spontaneous covalent growth of monomolecular adlayers on boran-doped diamond (BDD) thin films is described. The data obtained disclosed a large orientational distribution of chromophores on the BDD surface, consistent with the mesoscopic morphology of the system.

The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40% at. Si was prepared in the form of a thin film in a dc magnetron sputtering chamber. Structural disorder was obtained from extended X-ray absorption fine structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray magnetic circular dichroism spectroscopy. The orbital moment was extraordinary high, 0.4[micro]B. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2 kJ/[m.sup.3]). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction. Index Terms--Amorphous materials, magnetic anisotropy, magnetic films, X-ray spectroscopies.

Investigations have been undertaken into the structural properties of thin epitaxial TbFe(sub2) and DyFe(sub2) films with the influence of structure on their magnetic properties. Varying rates of residual tensile strain were observed in the films, and a splitting of the (220) Bragg reflection into a strain free component was revealed by x-ray diffraction. The strained component is attributed to the differing thermal expansions of the sapphire substrate and the TbFe(sub2) film.

Polarized neutron diffraction measurements were undertaken on a range of (111)Co (7.5nm)/CoO (X nm) and CoO (X nm) thin films, to study the antiferromagnetic (AFM) spin structure close to the interface of exchange-biased bilayers. Field cooling through the Neel temperature of the AFM increases the CoO moment component perpendicular to the applied field. The further application of a 500 Oe field perpendicular to the cooling direction, rotates the Co and CoO moments.

The thickness dependent spin-polarized electronic structure of thin and ultrathin films of Gd is distinguished by changes in the critical lambda exponent in the formalism of finite size scaling. The reduced critical exponent is correlated to increased prominence of surface magnetic structures, and the increasing paramagnetic-like bulk behaviour.

An investigation of strain-induced lattice distortion effects of as-grown and postannealed ultrathin La(sub0.6)Sr(sub0.33)MnO(sub3) epitaxial films grown on LaA1O(sub3) (001) substrates by pulsed laser deposition, on their crystal structure and transport properties, has been undertaken. The out-of-plane and in-plane lattice parameters of the sample were measured using conventional 0-20 x-ray scans with momentum transfer (q) along the (001) direction, with 0-20 scans of the (103) and (113) peaks, revealing a fourfold symmetry, consistent with a tetragonal unit cell.

SmCo based high coercivity films have been deposited by sputtering by several variants. Many magnetically sensitive materials are readily deposited by pulsed laser deposition (PLD), and it is shown that SmCo films can be produced directly by shadowed PLD onto heated substrates. Film reactivity with contaminating background gases was expected to rise at higher substrate temperatures.

We report results of a quantitative investigation of MFM sensitivity vs. tip coating thickness. Etched Si tips on cantilevers 225 [[micro]meter] in length were sputter-coated with Co-Cr films of various thicknesses 150 [Angstom] < t < 1500 [Angstrom]. Tip response was measured by scanning a specially-written hard disk with tracks of selected bit reversal densities. Tracking the shift in cantilever resonant frequency caused by the disk stray fields gave a measure of relative sensitivity, and hence tip moment. The main finding is a roughly linear increase in sensitivity (effective moment) up to a critical film thickness near 500 [Angstrom] beyond which saturation occurs. For 500 [Angstrom] coatings, sensitivity varies about 15% from tip-to-tip, indicating the degree of uniformity that can be expected from batch fabrication. We estimate the effective tip moment to be about [10.sup.-12] emu, implying that only a small portion of the tip's magnetic volume plays a role.

In this paper, track edge overwrite characteristics in planar isotropic longitudinal thin film media were studied by direct magnetic force microscopy imaging of the edge overwrite patterns. It is found that edge erasure strongly depends on the phase difference between the transitions in the overwriting and overwritten tracks at track edges. If the transitions in the adjacent tracks are in-phase, there exists no edge erase band and transitions in the adjacent tracks area connected in the side written band. Edge erasure occurs when there exist sufficient large phase difference between the transitions in the adjacent tracks. This new understanding of phase dependence of edge overwrite could have strong impact to the system design in terms of consideration for both PES and recording off-track performance.

High-rate reactive dc magnetron sputtering was applied to generate FeTaN/SiO2 multilayer and FeTaN single-layer films. The high frequency permeability functions, magnetic properties and the structure were estimated by analyzing the film geometry. The number of bilayer units, SiO2 spacer thickness and FeTaN layer thickness of the single-layer, bilayer and multilayer set of films were observed.

The experimental observation on a threshold thickness of crystallization below which the crystallinity of the films drops precipitously in spin cast films of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer is presented. This threshold thickness is directly linked to the crystal lamellar size along the film thickness direction.

Micromagnetic modeling is utilized to study the gyromagnetic switching limitations in thin film media. The dependence of switching time on film microstructures under uniform applied field is quantitatively investigated. For media with same [M.sub.r]t, reducing the film thickness and increasing intergranular exchange Coupling reduce the switching time at damping constants [Alpha] less than 0.1. The effect is more significant for smaller [Alpha] values. Oriented media has a longer switching time than isotropic media does. Index Terms--Gyromagnetic switching, switching time, thin film media, micromagnetics

The article discusses research methods used to ascertain the different results of surface effect when liquid crystalline thin films are captured and held in nanoscale cavities.

An analysis of surface roughness and its impact on the heat transfer process of spray cooling ignores evidence of other processes that generate nucleation in liquid films and focuses solely on heterogeneous nucleation as the process inducing nucleation. The hypothesis of the presence of an ultra-thin liquid film lacks experimental basis.