Si, Ge, SiC, and diamond samples were implanted with H 2 ϩ at 120-160 keV with 5.0 ϫ10 16 ions/cm 2 ͑corresponding to 1.0ϫ10 17 H ϩ ions/cm 2) and annealed at various temperatures to introduce hydrogen filled microcracks. An effective activation energy was determined for the formation of optically detectable surface blisters from the time required to form such blisters at various temperatures. The measured effective activation energies are close to the respective bond energies in all four materials. The time required to completely split hydrogen implanted layers from bonded silicon substrates and to transfer them onto oxidized silicon wafers is a factor of about 10 longer. Both processes, blister formation and layer splitting, show the same activation energy.

Abstract:The fabrication of a supported and insulated quantum wire would be of great interest, especially if electronic information could be accessed to determine charging and conductivity profiles. The feasibility of forming one-dimensional configurations of zz 15 nm gold colloids and 2.4 nm gold clusters via template methods of synthesis has now been demonstrated. The template host material consisted of porous alumina membranes formed by an electrochemical anodic process. The pores of the membrane, and hence the parallel pore channels, were packed in a hexagonal array. Alumina membranes are excellent template materials because of their high degree of order, thermal and chemical stability, and optical clarity. Pore diameter was controlled by regulation of the applied anodic potential (ca. 1.4 nm V -I ) . The pore channels were filled by one of three methods: vacuum induction (colloids only), electrophoresis (clusters only), or immersion (clusters, which were then converted into colloids by heating). Rudimentary wires consisting of colloids and clusters were successfully formed. In both cases, the diameter of the pore channel exceeded that Keywords clusters * colloids * goldnanostructures * quantum wires of the clusters or colloids. The wires thus formed conformed to the pore channel by forming helical secondary structures. It was not possible to form contiguous wires of clusters by immersion, or of colloids formed from clusters after heating. Composites (consisting of the gold-alumina system) were a bright scarlet color with an absorption maximum (A, , , , , ) at 519.5 nm. This is an unexpected result for spherical and small-diameter (10 nm) gold colloids, which normally absorb at i , , , 525-530 nm, a ruby-red color. Possible causes of this small but remarkable blue shift are discussed below. A new Au,, cluster ligand system consisting of a silsesquioxanederivatized thiol is also described.

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Ordered gold nanoparticle arrays with high lateral density of 6.87 × 1010 nanoparticles cm−2, which are stable up to temperatures of 600 °C, were fabricated. To this end, nanoparticles formed by thermal vacuum evaporation of Au were immobilized within the pores of nanoporous silicon wafers prepared by block copolymer lithography coupled with dry plasma etching. Even after high-temperature treatment the degree of order imposed by the block copolymer template was retained. Optionally, a nanoporous silicon nitride mask can cover the nanoporous silicon.

Persistent form modifications of silver nanoparticles in glass and the resulting dichroitic color changes induced by irradiation of a single intense femtosecond laser pulse were studied by means of high-resolution electron microscopy and spatially resolved optical transmission spectroscopy. Electron microscopy reveals a variety of morphological changes of the silver particles, in particular irregularly shaped particles surrounded by halolike structures consisting of very small silver clusters. The spectral analysis suggests that at lower intensities preferably desorption of silver into the glass matrix occurs producing isotropic spectral changes, while at higher intensities anisotropic spectra caused by particle deformation are observed. An analysis of the effects produced by different laser wavelengths allows one to correlate these findings with the variations of particle sizes depending on their penetration depth.