Papers by Keyword: Self-Organization

Abstract: The self-organized nanotube arrays were fabricated in glycerol electrolyte containing different additives, such as deionized water or ethylene glycol. The effects of anodization conditions, including anodic voltage, electrolyte viscosity, additives and ion concentration on the pores size and morphology were studied. Combined with preoxidation process, high aspect ratio titania nanotube arrays were formed rapidly in glycerol and saturated NaF solutions at 60 V for 1 h. SEM observation showed that a film with the thickness of about 10μm was obtained. A possible mechanism of the nanotubes growth was presented.

Abstract: The substructure evolution was observed in the range of scales from dozens nanometers to millimeters on the surface of the aluminum single crystalline plates under restricted cyclic tension. The self-similar systems of crossing bands that create the grid-like ordered structures on different scales are assumed to be clear manifestation of their self-organization. The selforganization of these grid-like structures is assumed to be inevitably related to the crystal structure defects (dislocations, point-like defects and their ensembles). The model is proposed for explanation of 2-dimensional rectangular "tweed" and 3-dimensional rhombic "pullover" pattern formations which are related to cooperative arrangement of crystal structure defects.

Abstract: In this work, a methodology, based on a self-organization process, to form gold nanoclusters on the 6H-SiC surface, is illustrated. By scanning electron microscopy and atomic force microscopy the gold self-organization induced by annealing processes was studied and modelled by classical limited surface diffusion ripening theories. These studies allowed us to fabricate Au nanoclusres/SiC nanostructured materials with tunable structural properties. The local electrical properties of such a nanostructured material were probed, by conductive atomic force microscopy collecting high statistics of I-V curves. The main observed result was the Schottky barrier height (SBH) dependence on the cluster size. This behaviour is interpreted considering the physics of few electron quantum dots merged with the ballistic transport. A quite satisfying agreement between the theoretical forecast behaviour and the experimental data has been found.

Abstract: This paper describes our recent achievements in fabricating various kinds of nanowires of silicon-based materials including beta iron-silicide, silicon carbide, and silicon germanium. Some of them can be grown directly at one-step process, while the others can be fabricated using nanowire templates. We discuss their structures, growth mechanisms, and properties based on electron microscopy observations.

Abstract: The growing importance of high integration on electronics demands novel interconnection methods replacing high-cost solder bumping or less reliable conductive adhesives. Self-organizing interconnection process using resin containing solder fillers has a possibility to achieve high-density joints satisfying both needs. Numerical study visualized the process and revealed that surface tension of molten fillers and resin viscosity determine the speed of conductive path formation.

Abstract: Thin-film titania templates were fabricated under different processing conditions. The dependencies of pore morphology and pore formation rate on process parameters were evaluated. It was found that under optimized electrolyte condition and anodizing voltage, a self-organized nanostructure consisting of porous TiO2 was obtained. 1 M Na2SO4 solution with the addition of 0.35 wt.% NaF and voltage potential of 30V were used. SEM images of templates showed very thin layer of ~70 nm thickness with worm-like pores. Pore diameter and average pore spacing of center to center on the surface were ~10 nm and 20 nm, respectively. The nanoporous TiO2 thin film will be very useful gas sensing and photocatalytic materials due to their large surface areas and high reactivities.

Abstract: Soft-nanotechnologies are based upon the synthesis technologies of nanomaterials and construction technologies of nanostructures by life forms. They are expected as new preparation methods for biomaterials that could be recognized as regular extracellular matrices (ECM) in our body by cells. We applied the soft-nanotechnology to synthesis of artificial bones made of HAp and collagen with bone-like nanostructure and examined their physical and biological properties. The nanocomposite obtained indicates bone-like nanostructure. Computer simulation and FT-IR suggested that the self-organization of HAp and collagen is based on chemical interaction between calcium ions on HAp surface and carboxy groups on collagen. After implantation in rats and dogs, the nanocomposites are resorbed by osteoclasts followed by osteogenesis; therefore, the nanocomposites are recognized as bone in the living body. Resorption rate can be controlled by crosslinkage. We also prepared sponge-like elastic porous body by gel-lyophilization technique using additional small amount of collagen solution. Bone tissue reactions of it are the same as the nanocomposites as prepared. The nanocomposites are now in clinical research in Japan to be commercialized in near future by Pentax Co.

Abstract: The novel selective interconnection using the resin containing low-melting-point-alloy fillers was developed as a high density assembly method of a low-temperature and highly reliable electronic interconnection. By means of the coalescence of fillers and wetting onto the terminal material due to the Laplace pressure of the fillers, self-organization onto the terminals was formed. The influence of the filler volume ratio and resin viscosity on the self-organized interconnecting was investigated by the numerical analysis with a multi-filler dispersion model corresponding to a real process, and was evaluated by using the normalized parameter (self-organization ratio). We clarified the existence of the optimal value of the filler volume ratio. The rate controlling factor transferred from the filler volume to the inflow velocity by the increase of the viscosity.

Abstract: The paper gives an overview of recent research activities that explore new pathways to achieve selective structurization of semiconductor surfaces by electrochemical deposition or dissolution techniques. Of a particular emphasis are pathways that are based on a two step procedure: First, locally a semiconductor surface is selectively activated (or de-activated) using techniques with a high lateral resolution (focussed ion electron beam, or AFM). In a second step, an electrochemical reaction (dissolution or material deposition) is selectively carried out at sensitized surface locations. Different examples of this strategy are given including selective suppression of a surface by damage induced amorphization. Additionally, smart structuring approaches involving self-organization of deposition or dissolution processes are shortly discussed.

Abstract: A self-organization model for repartition of dislocation cell structures and transition of subgrains on a three-stage hardening of single crystal are developed. Stress-effect coefficients models are proposed in order to introduce stress information into the reaction-diffusion equations. A FD simulation for dislocation patterning and a FE one for crystal deformation are simultaneously carried out for an FCC single crystal. It is numerically predicted that a cell structures are repartitioned and the generated dislocation pattern in stage III can be regarded as a subgrain.