Solid State Phenomena Vols. 97-98

Abstract: The adsorption of organic molecules on solid surfaces is one of the fundamental processes for the development of molecular-based nanodevices. Here we focus on the adsorption and ordering of the TPPS₄-based J-aggregates on silicon and gold as well as on self-assembled monolayer (SAM) surfaces. The SAMs used for the experiments were based on the chemisorption of thiol containing compounds onto gold. Long ω-substituted alkanethiols are spontaneously assembled on gold to form highly ordered and densely packed layers with controllable chemical and physical properties. TPPS₄ J-aggregates were dispersed on SAM surfaces, and on plain gold and silicon substrates for comparison. The dimensions of aggregates, measured by means of atomic force microscopy, varied depending on the type of substrate. Long stripe-like aggregates were flattened on the substrate surface, and the height and width of aggregates highly correlated with the polarity of surface groups. For example, the J-aggregates were narrower on hydrophobic substrates (with non-polar groups) and wider on hydrophilic substrates (with polar groups). These observations support the hypothesis, that TPPS₄ forms .soft. cylindrical aggregates, that appear flattened on the substrate.

Abstract: The linear and nonlinear optical properties of pure 3,3'-bis(3-carboxypropyl)-5,5',6,6'- tetrachloro-1,1'-dioctylbenzimidacarbocyanine (C₈O₃) aggregates as well as of C₈O₃ aggregates in the presence of PVA are studied at room temperature. The obtained results reveal that absorption spectra of both aggregates are governed by four absorption bands. Three of these represent transitions having dipole moments oriented parallel to the axis of the aggregate and one oriented perpendicular to it. The two lower energy parallel transitions are found to be weakly coupled which suggests that they represent two excitons located on different walls of the double-wall cylinder. In contrast, the lowest energy parallel transition and the transition having a transition dipole moment oriented perpendicular to the aggregate axis share the same ground state which reveals that they belong to the same exciton band. The manner of modification of the linear absorption with addition of PVA as well as the similarity of the pump-probe spectra of the two investigated aggregates suggests that this exciton band originates from the inner wall of the double-wall cylinder.

Abstract: The structural and optical properties of the gel-forming photochromic switch 1,2-bis(2’-methyl-5’-{{((R) phenylethyl)amino}carbonyl}thienyl-3’-yl)cyclopentene are studied by means of the linear absorption and holographic grating techniques. The use of diffractive optics enables recording of holographic gratings with high long-term phase stability. The diffraction efficiency of the recorded holographic gratings approach values of 30% for low writing beam energies when diffusion is the rate determining factor. At higher writing pulse energies the competition between the diffusion and photodecomposition processes causes lower diffraction efficiencies. At irradiation doses above 10 mJ the spatial profile of the recorded gratings is strongly influenced by saturation effects. Because of the well-determined grating profile the holographic grating technique is potentially applicable for the quantitative characterisation of the diffusion process in photochromic gels.

Abstract: The model of the evolution of nano- and microstructures in the self-formation process of underetching (lateral etching) layers was created for analysis and design of new self-alignment and self-formation technologies semiconductor devices and integrated circuits. The program was realized on the basis of a personal computer with the processor INTEL PENTIUM 4 and MATLAB 5.3 software. The results of the simulation were given for the different initial configurations of nanostructures. The experimental investigations evolution of microstructures in lateral etching processes of amorphous and polycrystalline films were performed and the results presented.

Abstract: An understanding of both the interactions between the adsorbate molecules and the interactions between adsorbates and the surface is a prerequisite to eventually controlling the selfassembly process in supramolecular aggregation. Here we report the formation of supramolecular structures (J-aggregates) whose size and aggregation pattern are controlled by changing the number of polar sulfonic groups of meso-tetra (4-sulfonatophenyl) porphine. Using atomic force microscopy we show that substituted porphyrin molecules (5,10,15,20-tetrakis(4-sulfonatophenyl) porphine (TPPS₄), 5,10,15-tris(4-sulfonatophenyl)-20-phenyl porphine (TPPS₃), 5,15-bis(4-sulfonatophenyl)- 10,20-diphenyl porphyne (TPPS_2op) - SO₃ groups are opposite each other, and 5,20-bis(4- sulfonatophenyl)-10,15-diphenyl porphyne (TPPS2a) . SO₃ groups are adjacent each other) form different spatial structures. Our findings suggest that placement of functional groups that are participating in direct noncovalent interactions will allow design and construction of different supramolecular structures adsorbed to surfaces.

Abstract: The mechanism and conditions of meso-tetra (4-sulfonatophenyl) porphine (TPPS₄) molecular aggregate formation and their geometrical structure are investigated by methods of molecular mechanics and quantum chemistry. J- type aggregates are formed of zwitterionic forms of TPPS₄ via interaction of their positively charged porphyrin rings and negatively charged SO₃ - groups. According to ab initio and PM3 calculations it was found that TPPS₄ zwitterion has asymmetrical structure (parts of porphyrin ring are asymmetrically bent out of plane), although the porphyrin ring of TPPS₄ molecule in neutral aqueous solution (at pH 7) is flat and the planes of phenyl rings are nearly perpendicular to the porphyrin plane. We propose that asymmetrical porphyrin rings are able to form bent threads. The thread is bent approx. 5° for each monomer, so approximately 60 monomers should form the loop (diameter ~20 nm).

Abstract: The analysis for basic processes of self-formation microstructure in technologies of manufacturing semiconductor devices and integrated circuits (IC) have been made and the requirements have been formulated. The results of the implementation of self-formation processes for creating new technologies of manufacturing semiconductor devices and IC have been presented.

Abstract: A model of the evolution geometry technological masks and underlaying layers in the lateral etching processes is created for analysis and design of new self-alignment and self-formation technologies semiconductor devices and integrated circuits. The results of the simulation for the different configurations masks and selectivities of the underlaying layers have been presented.

Abstract: Most of researchers at research of "self evicted vibrations" in machining state that they are resulted by passing of force stability boundaries of the mechanical system at which oscillations increase hardly. Explanations of process development from the point of view of grinding dependencies are absent. The article is allotted to analyze the process in time, it is shown how in result of action of forced vibrations with frequencies different from any natural frequency of the system new vibrations with some natural frequency of the system are propagated. New properties of the system are formed. Equations are deduced and calculation results are presented in the article.

Abstract: We have studied transmission and linear dichroism spectra of synthetic opal, refractive index n_- = 1.342, infiltrated with nematic liquid crystal with averaged refractive index n = 1.596 or with water n = 1.30 and alcohol n = 1.28. We demonstrating that the position of the stop band in the visible spectra is shifted by changing infiltrated material, or temperature, or by variation angle of light incidence. Multiple diffraction are discussed.