Temperature and external field-driven microrelief at free surface of smectic-A liquid crystal

A homeotropically oriented smectic-A film on a solid substrate with periodical microrelief is considered. Periodical distortions of the free surface of the film induced by this microrelief are theoretically investigated. The dependence of these distortions on the film thickness, the temperature, and external magnetic (electric) field is obtained. It is shown that, for a certain choice of the shape of the substrate surface microrelief, one can realize a temperature and external magnetic (electric) field control on the microrelief at the free surface of the smectic-A film.     

Nature of the electric forming of a thin film metal-dielectric-metal system

The influence on forming is considered in the paper of voltage, microrelief of the base electrode (BE), and width and technology of obtaining of a dielectric layer of an MDM-system. The presence is estabished experimentally of a critical width of a dielectric, depending on the microrelief of the BE, an increase of which makes forming impossible — only a breakdown is observed. Relying on the experimental results obtained, an inference is made that the most essential factors determining forming are the presence of a specific microrelief of the BE or defects of the dielectric film (cells, microfissures, et al.) and a specific correlation of the width of the dielectric film with the dimensions of the indicated microdefects.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 65–67, January, 1991.     

Microrelief dependent on the temperature and external field on the free surface of a smectic-<Emphasis Type="Italic">A</Emphasis> liquid crystal

A homeotropically oriented smectic-A film on the surface of a solid substrate with a periodic microrelief is considered. Relationships are derived for describing the dependences of the microrelief-induced deformation of the free surface of the film on the film thickness, the temperature, and the external magnetic (electric) field strength. It is shown that, for a specific choice of the microrelief shape on the substrate surface, a variation in the sample temperature and the external magnetic (electric) field strength makes it possible to control not only the microrelief depth but also the shape of the microrelief formed on the free surface of the smectic-A film.     

Structure of the surface microrelief of a droplet evaporating from a rough substrate as a possible cause of contact angle hysteresis

Based on the refraction images of a droplet evaporating on a rough substrate, we simultaneously observed the dynamics of its surface microrelief, contact angle, and contact line deformations along the entire perimeter of the contact line. This has led us conclude that the microrelief structure is directly related to the phenomenon of contact angle hysteresis and the jump-like pattern of contact line deformation. We suggest a possible mechanism for the occurrence of contact angle hysteresis during droplet evaporation and derive the relations that specify the range of possible contact angles at known microrelief parameters.     

High-precision calculation of quasistatic field near a photocathode surface microrelief

In modern photoelectron devices, the problem of the impact of photocathode roughness on a photoelectron beam and the characteristics of the devices is extremely challenging. Through a three-dimensional (3D) field determination near a photocathode surface microrelief, the high-precision dynamics of photoelectrons from a photocathode can be determined and the influence of photocathode surface roughness on photoelectron beam characteristics can be investigated. The combined analytical–numerical method of field determination presented in this paper can be used in the investigations. In contrast with FEM method, the combined analytical–numerical method can calculate the field with a heightened accuracy and in a shorter time using a PC. The method can be applied to both arbitrary surfaces and a class of realistic microrelief surfaces. In the latter, it is possible to accelerate the speed of calculations through analytical developments of the method. For another class of microrelief surfaces, it is possible to formulate an analytical solution for field determination without numerical computations. Typical precisions and computation times of the written code were presented, comparison with a commercial code based on FEM method was done, and features of the method related to numerical instabilities of the code were discussed. A method of eliminating the instabilities was proposed.     

Sulfide passivation of a textured interface of a gallium arsenide surface-barrier photovoltaic cell

A comparative study is made of the influence of sulfide passivation in an aqueous Na₂S·9H₂O solution on the photoconversion parameters of solar radiation in Au-GaAs barrier structures as a function of the character of the microrelief and the pretreatment of the GaAs surface. A quasigrating and a dendritic surface microrelief were produced by anisotropic chemical etching. It is shown that this type of GaAs surface treatment is potentially useful for enhancing the efficiency of a photovoltaic cell stored for several years. A possible mechanism is discussed for the processes leading to changes in the structure parameters. Zh. Tekh. Fiz. 69, 132–134 (June 1999)     

Surface microrelief smoothing mechanisms in a target irradiated by an intense charged particle beam

Physical mechanisms and a mathematical model are proposed to describe the smoothing of the microrelief of an irradiated surface. Before melting, smoothing is caused by elastoplastic deformation of the material; after the melting of the surface layer of the irradiated target, smoothing is caused by the dynamics of the target boundary under the action of surface tension forces, viscous forces, and inertial forces. The results of numerical simulation agree qualitatively and quantitatively with experimental data. The proposed mathematical model can be used to predict changes in the microrelief of the irradiated surface and to choose irradiation conditions when solving the problems of radiation technologies.     

Application of correlation speckle photography for measuring contact pressures

A method for measuring contact pressures based on the measurement of irreversible changes in a surface microrelief by the speckle photography technique is presented. The analytic dependence between the change in the contrast of the carrying Young’s fringes and the relative area of change in the microrelief is considered. An example of a contact interaction between a cylinder end and a flat slab, the latter with a specially produced regular roughness on its contact surface, is used to experimentally verify the relation between the irreversible change in the roughness, the change in the contrast of the holographic interference fringes, and the change in the contrast of the carrying Young’s fringes. It is shown that the sensitivity of correlation speckle photography is higher than the sensitivity of the correlation holographic interferometry technique.     

Morphology and interfacial properties of microrelief metal–semiconductor interface

The effect of the morphology of Au/GaAs interface microrelief, prepared by chemical anisotropic etching, on current flow mechanism, electronic and recombination properties of interface has been investigated. Simulation of I–V curves and optical transmittance of light into semiconductor was made on the basis of the developed theories taking into account the barrier height distribution and the effect of scattering of light by low microrelief.     

Investigation of secondary-emission signal formation in the low-voltage SEM mode

We present the results of studying secondary-emission signal formation in a scanning electron microscope; the signal is generated by the surface microrelief under an accelerating voltage of 0.3–3 kW with the detection of all secondary electrons.     

The technology of fabricating focusators of infrared laser radiation

The possibility of fabricating focusators of infrared laser radiation, based on photolithographic technology, is analysed. The realizability of focusator fabrication is based on the possibility of producing a set of binary photomasks and achieving the necessary depth of etching the substrate of the pattern while forming the microrelief. The possibility of producing these photomasks is evaluated with regard to the focusator's extremal zone width and the appearance of photomasks displayed on the screen. Forming of step-by-step microrelief is achieved using plasma etching or wet etching and depends on the minimum element's dimension and the etching depth. Examples of the microrelief's profiles, of focusators fabricated using photolithography, and the result of the transformation of a focusator's radiation into a straight line segment, are discussed.     

Minimization of the Total Depth of Internal Saw-Tooth Reliefs of a Two-Layer Relief-Phase Diffraction Microstructure

Results of studying the possibility to decrease the total depth of reliefs of a two-layer microstructure having two internal saw-tooth microreliefs reducing the dependence of the diffraction efficiency of the microstructure on the radiation wavelength and angle of radiation incidence on the microstructure are presented. These results allow one to minimize the complexity of obtaining optimum microrelief depths depending on requirements applicable to the diffraction optical element in the framework of the electromagnetic-diffraction theory. Optimum depths provide in the specified spectral range and interval of angles of radiation incidence the maximum possible (for the chosen width of the narrowest zone of the saw-tooth microrelief) value of the diffraction efficiency at the point of its minimum.     

On the formation of a wavy microrelief on an ion-beam-sputtered semiconductor surface

A mathematical model of regular wavy microrelief formation on a semiconductor surface subjected to an obliquely incident medium-energy ion be am is stated and analyzed. Taking into account the influence of fluctuation forces (the molecular component of the disjoining pressure) and of the ion-beam-transferred electric charge is shown to bring together model predictions and observations.     

X-ray microanalysis of polyvinyltrimethylsilane surface after impact of accelerated oxygen plasma flow

The elemental composition and surface structure of polyvinyltrimethylsilane exposed in oxygen plasma flow accelerated to an energy of 20–30 eV are studied by scanning electron microscopy and X-ray microanalysis. A microrelief is developed on the surface of the material reflecting its fibrillar supramolecular structure: the oxygen concentration increases, but the carbon concentration decreases. The surface is contaminated with Cu and F atoms as a result of their emission to the plasma due to the wear of the accelerator components.     

Role of the electric potential in the creep acceleration and formation of Al fracture surface

Aluminum creep acceleration at applying an electric potential to ±1 V has been established experimentally. The fracture surface and side surface microrelief near the fracture surface were investigated by scanning electron microscopy. It is shown that application of ±1 V potential leads to decrease in the fracture toughness. Possible reasons for this phenomenon are considered.     

Effect of microrelief on the optical characteristics of light Cr-Zr copper alloys bombarded by ions of deuterium plasma

The effect of the structure and size of grains on changes in the microrelief and optical characteristics of specimens of mirrors made of copper alloys with substantially differing grain size upon bombardment by ions of deuterium plasma are studied. Based on a comprehensive study of the structural features of the surface layers of specimens of mirrors made of light copper-chromium alloys, a conclusion is drawn as to the determining role of grain size in their radiation properties.     

Effect of gamma irradiation on photoconversion characteristics of metal/gallium arsenide barrier structures with textured interface

The effect of ⁶⁰Co gamma irradiation at doses of 10³-2×10⁵ Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating) obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer higher efficiency and radiation resistance.     

Margination of white blood cells in microcapillary flow

Margination of white blood cells (WBCs) towards vessel walls is an essential precondition for their efficient adhesion to the vascular endothelium. We perform numerical simulations with a two-dimensional blood flow model to investigate the dependence of WBC margination on hydrodynamic interactions of blood cells with the vessel walls, as well as on their collective behavior and deformability. We find WBC margination to be optimal in intermediate ranges of red blood cell (RBC) volume fractions and flow rates, while, beyond these ranges, it is substantially attenuated. RBC aggregation enhances WBC margination, while WBC deformability reduces it. These results are combined in state diagrams, which identify WBC margination for a wide range of flow and cell suspension conditions.     

Influence of filler type on wet skid resistance of SSBR/BR composites: Effects from roughness and micro-hardness of rubber surface

The wet skid resistance (WSR) of SSBR/BR(solution styrene-butadiene rubber/butadiene rubber) composites filled with carbon black, silica, and nano-diamond partly replacing carbon black or silica, respectively, was measured with a portable British Pendulum Skid Tester (BPST). A dynamic mechanical thermal analyzer was used to obtain the viscoelasticity of the composites. A 3D scanning white-light interfering profilometer was used and the scratch test performed to characterize surface roughness and micro-roughness, respectively, of the composites. WSR of the silica-filled composite was better than that of the carbon black-filled one, and further enhancement of WSR was obtained by replacing silica with nano-diamond. Tan δ of the composites at 0 °C, 10 Hz, and tensile strain of 2% did not show good correlation with WSR. The surface roughness of the composites had effects on WSR. The scratch test indicated that the higher the hardness of the filler in the composite, the higher the micro-hardness and the better the WSR. Therefore, the surface micro-hardness of the composites is an important factor affecting WSR, besides viscoelasticity and surface roughness.