Solid State Phenomena Vols. 124-126

Abstract: We introduce a novel and versatile approach for controlling anti-reflective (AR) properties of multilayer films based on layer-by-layer (LbL) self-assembly (SA) method. For the fabrication of these films, blend (i.e., mixed) layers containing both polyanions (i.e., titanium precursor (TALH) and poly(sodium 4-styrenesulfonate) (PSS)) were assembled with polycation (i.e., poly(diallyldimethylammonium chloride) (PDAD)) for the formation of the high refractive index multilayers and on the other hand, the negatively charged silica particles with the diameter of about 100 nm were employed for low refractive index layer. The refractive index of TALH:PSS/PDAD multilayer was controlled by blending ratio and annealing temperature as TALH has the relatively high refractive index (n = 1.68) in comparison with that (n = 1.46) of conventional polyelectrolytes (PEs) at room temperature and furthermore these titanium precursors are partially changed into TiO2 with relatively high refractive indices (n = 1.50 ~ 1.81) at annealing temperature of 250 oC. In the case of silica particle layer used for low refractive index layer, the calculated refractive index was about 1.35 due to much vacancy among the adsorbed silica colloids although the inherent refractive index of silica material is about 1.45. As a result, the films composed of TALH:PSS/PDAD multilayers with tunable refractive index and silica colloidal layer can easily modulate the optical properties of multilayer films by blending ratio and heat treatment.

Abstract: Well-controlled cubic nanocrystal of TMA-A zeolite with a size of 60~100 nm were synthesized by a hydrothermal method in a solution having a Al(i-pro)3 : 2.2 TEOS : 2.4 TMAOH: 0.3 NaOH : 200H2O composition. The single TMA-A nanocrystals has an average lattice constant of 24.61 Å having a surface area of 742.36 m2/g. Thermal treatment of TMA zeolite crystals results in the formation of an amorphous above 900oC. Environmental scanning electron microscopy (ESEM). high resolution transmission electron microscopy(HRTEM), X-ray powder diffraction(XRD), fourier transform infrared(FT-IR) spectroscopy, DTA/TGA and BET analysis were used to characterize the initial materials and the obtained products after various heat treatments.

Abstract: The high-resolution scanning electron microscopy (HRSEM) image showed that selfassembled ZnSe small quantum dots (QDs) and large nanodots with a pyramid shape were formed in the Cl-doped ZnSe epilayers grown on GaAs (100) substrates. The formation of the ZnSe QDs was attributed to three-dimensional growth controlled by distribution of the impurities in the Cldoped ZnSe epilayrs. Cathodoluminescence (CL) measurements at room temperature revealed the emission peak at 3.1 eV corresponding to the blue shift approximately 400 meV from the near band edge emission of 2.7 eV in the bulk ZnSe. The blue shifted CL peak indicates the quantum confinement effect resulting from the formation of the ZnSe QDs in the Cl-doped ZnSe thin film. While the peak position of the donor-acceptor pair emission shifted to higher energies with decreasing temperature, the band-edge emission peak for the QDs did not significantly change.

Abstract: In this study, morphology control of ZnO was performed by a wet chemical processing without templates at room temperature. In special, the effect of aging time and pH of this wet processing on ZnO morphologies was in detail investigated. As a result, products composed of a single phase of ZnO with a unique morphology like a hollow tube were obtained. Then, it was found that an aging process played an important role on controlling morphology of ZnO during this wet chemical process. Furthermore, it was found that this hollow-tubular ZnO had a high transparency.

Abstract: ZnO nanostructures have been synthesized on graphite substrates by thermal evaporation of ZnO powder without a metal catalyst at a temperature of 1300
. The colors of the as-synthesized products gradually change from white and brown to gray as the distance from the source material increases. ZnO particles were formed at higher temperature region. ZnO particles gradually changed into ZnO nanowire as the temperature decreased. Finally, ZnO nanowires disappeared completely and only Zn particles were observed at lower temperature region.

Abstract: We synthesized the polymer brushes by conventional free radical polymerization and investigated the morphology evolution of block copolymer nanostructure on the brush treated surfaces. Our simple approach utilized a functionalized free radical initiator to add hydroxyl group to a chain end and an excess amount of a chain transfer agent to control the molecular weights of the brushes. The synthesized polymer brushes had narrow molecular weight distribution as well as hydroxyl end group and were successfully grafted onto silicon oxide layer by simple spin-coating and annealing process. The orientation of poly(styrene-block-methyl methacrylate)s (PS-b- PMMAs) coated on the brush grafted surface was finely controlled by the surface modification by polymer brushes.

Abstract: We present a phase field model for coherent phase transition and its application to the self-assembled arrangement of second phase particles in coherent phase transition. The model developed here is free from the interface instability due to the contribution of chemical free energy and correctly describes elastically inhomogeneous system. It is observed that coherent misfit strain and anisotropy of elastic constants induce the interface instability that brings about the particle splitting and the self-assembled alignment of second phase particles. Their arrangement to the elastically soft direction occurs only in the system where the elastic contant of the precipitates is larger than that of the matrix phase.

Abstract: The ZnO seed precursor was prepared by sol-gel reaction. ZnO nanorod arrays were fabricated by solution chemical deposition on ZnO coated seed substrates. The substrates used are Si wafer, glass and PET. The fabricated ZnO nanorod had hexagonal morphology, length of 400~500 nm and diameter of 25~50 nm. The ZnO seeds were indispensable for the aligned growth of ZnO nanorod. The ZnO nanorod growth was dependent on the seeding method used but independent of the substrates. The structure of ZnO nanorod was characterized by FE-SEM, XRD and FE-TEM. This method enables large scale growth of ZnO arrays on all kinds of substrates including polymers.

Abstract: We investigate the electrical conductive poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms and micropatterning prepared by vapor-phase polymerization method using self-assembling teacnique. The thin conductive films were uniformly fabricated between 20 and 100 nm, there surface resistance wasenhanced until to 102
/square, and the light-transmittance were also increased as up to 95 %. We report a fabrication of electrically conducting PEDOT pattern on a electrically insulating substrate using a microcontact printing method. Then, patterns are successfully obtained with line widths down to 3
.

Abstract: We synthesized a symmetric, fluorine-containing diblock copolymer of polypentafluorostyrene-b-poly(methyl methacrylate) (PPFS-b-PMMA) by atom transfer radical polymerization (ATRP). The PPFS macroinitiator was also synthesized by ATRP by using 1-phenylethyl bromide initiator. The chemical structure of the polymer was confirmed by GPC, 1H-NMR and DSC measurements. Due to the chemical dissimilarity between the PPFS and PMMA blocks, the microphase-separation was occurred during annealing at high temperature, displaying a lamellar morphology with a thickness of approximately 35 nm.