We report a novel approach for fabricating gold nanostar-functionalized substrates for highly sensitive surface enhanced Raman spectroscopy (SERS)-based chemical sensing. Gold nanostars immobilized on a gold substrate via a Raman silent organic tether serve as the SERS substrate, and facilitate the chemical sensing of analytes that can either be chemisorbed or physisorbed on the nanostars. Our SERS substrates are capable of detecting chemisorbed 4-mercaptobenzoic acid at a concentration as low as 10 fM with a reproducible SERS enhancement factor of 10(9), and enable the semi-quantitative multiplexed identification of analytes from mixtures in which they have been dissolved in variable stoichiometry. Most importantly, they afford the detection of physisorbed analytes, such as crystal violet, with an excellent signal-to-noise ratio, hence serving as a versatile platform for the chemical identification of in principle any molecular analyte. These characteristics make a strong case for the use of our nanostar-based SERS substrate in practical chemical sensing applications.

We report on the concentration, chemical bonding, and etching behavior of N at the SiC(0001)/SiO 2 interface using photoemission, ion scattering, and computational modeling. For standard NO processing of a SiC MOSFET, a sub-monolayer of nitrogen is found in a thin inter-layer between the substrate and the gate oxide (SiO 2). Photoemission shows one main nitrogen related core-level peak with two broad, higher energy satellites. Comparison to theory indicates that the main peak is assigned to nitrogen bound with three silicon neighbors, with second nearest neighbors including carbon, nitrogen, and oxygen atoms. Surprisingly, N remains at the surface after the oxide was completely etched by a buffered HF solution. This is in striking contrast to the behavior of Si(100) undergoing the same etching process. We conclude that N is bound directly to the substrate SiC, or incorporated within the first layers of SiC, as opposed to bonding within the oxide network. These observations provide insights into the chemistry and function of N as an interface passivating additive in SiC MOSFETs. V

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In the present work we report on the energy loss ratio R n of fast H 2 + clusters in thin films ͑30-50 Å͒ of LaScO 3 and HfO 2 . The medium energy ion scattering technique was employed covering a broad energy range ͑40-200 keV/amu͒. The energy loss ratio data showed no clear evidence of collective excitations in these materials. The experimental results were interpreted in terms of three different theoretical approaches: the dielectric formalism with the Brandt-Reinheimer theory for semiconductor materials; the detailed simulation of the molecular fragments dynamics through the target; and finally the unitary convolution approximation adapted for hydrogen molecules. Only the simulation agrees with the experimental results for both oxides. The unitary convolution approximation works quite well for HfO 2 but overestimates slightly the LaScO 3 data. The overall results indicate that the energy loss ratio depends critically on the description of the electronic properties of such oxides.

We present experimental and theoretical results of vicinage effects due to the interaction of H

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We have performed proton irradiation of W and W-5wt.%Ta materials at 350°C with a step-wise damage level increase up to 0.7 dpa and using two beam energies, namely 40keV and 3MeV, in order to probe the accumulation of radiation-induced lattice damage in these materials. Interstitial-type a/2 <111> dislocation loops form under irradiation, and their size increases in W-5Ta up to a loop width of 21(4) nm at 0.3 dpa, where loop saturation takes place. In contrast, the loop length in W increases progressively up to 183(50) nm at 0.7 dpa, whereas the loop width remains relatively constant at 29(7) nm and ≥0.3 dpa, giving rise to dislocation strings. The dislocation loops and networks observed in both materials at later stages act as effective hydrogen trapping sites, so as to generate hydrogen bubbles and surface blisters. Ta doping delays the evolution of radiation-induced dislocation structures in W, and consequently the appearance of hydrogen blisters.

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