We report the spontaneous formation of large spatial ordered patterns in a continuous aluminum ͑Al͒ film system deposited on silicone oil surfaces by a thermal evaporation method. The growth mechanism of the ordered patterns can be traced to a three-stage process, the first of which involves nucleation and growth of strips with a characteristic domain structure in the films. In the subsequent stage, triangle-shaped domains with different sizes appear in the strips. Then the domains grow and finally form the ordered and band-shaped patterns. The experiment shows that the ordered patterns result from the spontaneous ordered organization of the Al atoms and atomic clusters driven by the internal stress in this nearly free sustained film system.Spontaneous generation of complex order in apparently simple systems is of long-standing and continuing interest not only for its aesthetic appeal, but also for its fundamental and technological relevance. [1][2][3][4][5][6][7][8][9] In natural systems there are large varieties of self-organized phenomena that potentially span a wide range of scales, from macroscopic ground surface morphologies 1 and granular materials 2 to nanometerscale structures such as microporous materials, 3 nanocrystals ͑including nanoclusters, nanowires, nanotubes, etc.͒ in semiconductors, 4 nanostructure arrays on strained crystal surfaces, 5 and complex biological and nonbiological structures organized with supramolecules ͑or molecules͒. 6,7 Some previous studies demonstrated that the ordered patterns existing in thin films deposited both on solid substrates 5,10,11 and on soft polymer substrates 8,9 are induced by the buckling of the films owing to the relief of the internal stress.Vapor phase deposition of metals on liquid substrates was studied in a number of recent investigations. 12-15 It is observed that atoms, atomic compact clusters, and branched islands on liquid substrates possess large mobility and they can diffuse, rotate, and aggregate on the liquid surfaces freely. In principle, the phenomena resulted from the internal stress in continuous thin films deposited on liquid surfaces can emerge obviously because of the weak interaction between the films and the liquid substrates. Therefore it is expected that various characteristic patterns caused by the internal stress relief may appear apparently in these nearly free sustained films. 12 Here we report the spontaneous formation of large spatial ordered stress relief patterns existing in continuous aluminum ͑Al͒ films deposited on silicone oil surfaces. We anticipate that this nearly free sustained metallic film system subjected to the distinctive effect of the underlying liquid layers will provide a test bed not only for the fundamental research on the internal stress in the films, but also for the technological application of various free sustained films on liquid substrates.The samples were prepared by thermal evaporation of 99.999% pure Al in a vacuum of 6ϫ10 Ϫ4 Pa at room temperature. Commercial silicone oil ͑Dow Corning 705 Diffusion ...
We report on the spontaneous formation of hierarchical wrinkling patterns in Cr films deposited on silicone oil drops with constrained edges. The appearance of the wrinkling patterns is strongly dependent on the film thickness and the size of the silicone oil drop. Because the Cr film at the drop edge is constrained due to the strong adhesion between the film and the glass surface, the wrinkle wavelength merely depends on the distance starting from the drop edge. When the distance increases, the wavelength increases quickly first, and then it slows down gradually in compliance with a simple power law. The evolution of the wrinkle amplitude is similar to that of the wavelength, but it is also closely related to the film thickness and the oil drop size. Based on the fact that the silicone oil is polymerized to form an elastic layer during deposition, the formation and evolution of the hierarchical wrinkling patterns have been analyzed in detail.
We report the experimental observations of large spatially disk-shaped patterns in an iron (Fe) film system deposited on silicone oil surfaces by a DC-magnetron sputtering method. These disk patterns form spontaneously during deposition and grow successively in vacuum condition after deposition. Their nucleation, growth and evolution are strongly dependent on the sputtering power, deposition period and growth time. The experiment indicates that they may result from the spontaneous organization and gathering of the Fe atoms and atomic clusters driven by the internal stress.
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