X-ray and electron beam diffraction analyses have been carried out on thin films deposited from a beam of carbon ions. Results show that the films consist of a polycrystalline background of cubic diamond with a particle size of 50–100 Å with single-crystal regions up to 5 μm in diameter.

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SummaryAn outstanding example of biological pattern formation at the single cell level is the diversity of biomineral structures in the silica cell walls of the unicellular eukaryotic algae known as diatoms. We present a survey of cell wall silica structures of 16 diatom species, which included all major cell wall components (valves, girdle bands and setae), imaged across the nano-, meso-and microscales using atomic force microscopy. Because of atomic force microscopy's superior ability to image surface topology, this approach enabled visualization of the organization of possible underlying organic molecules involved in mineral structure formation. Diatom nanoscale silica structure varied greatly comparing the same feature in different species and different features within a single species, and frequently on different faces of the same object. These data indicate that there is not a strict relation between nanoscale silica morphology and the type of structure that contains it. On the mesoscale, there was a preponderance of linear structures regardless of the object imaged, suggesting that assembly or organization of linear organic molecules or subcellular assemblies that confine a linear space play an essential and conserved role in structure formation on that scale. Microscale structure imparted an overall influence over nanoand mesoscale structure, indicating that shaping of the silica deposition vesicle plays a key role in structure formation. These results provide insights into the design and assembly principles

The linewidth of bulk plasmons in a rapid-quench Al$Mn quasicrystal is found to increase by ~~ 40% as compared with that observed in a thermally annealed crystalline Al 6 Mn sample. A narrower plasmon linewidth is also observed in a sputtered amorphous A^Mn thin-film sample. We believe that the unusual plasmon line broadening in A^Mn quasicrystals is a result of increased interband transitions due to the icosahedral symmetry of the quasicrystal, and not a consequence of lattice disorder.PACS numbers: 7L45. Gm, 71.25.Mg, 79.20.Kz Since the exciting discovery of the isocahedral symmetry in rapidly quenched Al 6 Mn alloys (hAl 6 Mn) by Shechtman et ai} systems with icosahedral symmetry have captured the attention of physicists and material scientists around the world. The appearance of sharp diffraction spots can now be understood by a new class of ordered structures (quasicrystals) with quasiperiodic rather than periodic translational order. 2 Almost all papers published so far in this rapidly growing field have dealt with the lattice structure in one form or another in an attempt to unravel the ultimate mystery, i.e., exactly where the atoms are located in the lattice. On the other hand, experimental probes of the electronic properties of /-A^Mn have so far revealed nothing unusual. In this Letter we report the first experimental observation of the excitation spectra of the electron gas in Al-Mn quasicrystals by high-energy transmission electron-energy-loss spectroscopy (EELS), and we show a significant ( -40%) plasmon line broadening in the icosahedral phase as compared with that observed in its crystalline counterpart (cAl 6 Mn). We argue that this is due to the change of electronic structure in the ^Al 6 Mn phase.Samples of *-Al 6 Mn quasicrystals were made by induction melting of high-purity Al and Mn in boron nitride crucibles under argon atmosphere. Ribbons of -1 mm in width and 30 /xm in thickness were obtained by melt spinning in an argon atmosphere on a copper wheel. The thin-film samples for EELS were prepared by chemical thinning. Amorphous Al 6 Mn samples (-500 A in thickness) were prepared on rock-salt substrate by sputtering. EELS was carried out in a VG H5 100-kV scanning transmission electron microscope equipped with a Gatan 607 electron spectrometer. A 5-10 A electron probe was used to probe the electronic and chemical inhomogeneities in real space. An energy resolution of -0.7 eV was routinely obtained with a collection angle of ~~ 15 mrad. The energy-loss spectra were obtained by electrostatic scanning of the drift tube of the magnetic spectrometer and, therefore, precise peak positions could be determined.The application of microprobe analysis is most suitable for studies of Al-Mn quasicrystals which are formed through complex nucleation and growth FIG. 1. Plasmon spectra for Ai, oAl 6 Mn, #-Al 6 Mn, and /-Al 6 Mn.