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The fluorescence recovery after photobleaching technique (FRAP) was used to measure the diffusion coefficients (D) of fluorescein isothiocyanate (FITC)-dextrans in diluted, semidiluted, and concentrated hyaluronic acid solutions. The decrease of the diffusion coefficients as the hyaluronic acid concentration increases was consistent with the universal scaling equation D/Do = exp(-oc'). The diffusion experiments were carried out to obtain structural information on the transient network structure in hyaluronic acid solutions. On the basis of scaling laws, the concentration dependence of the average mesh size £ was determined as £ ~c-0•68*0•07. Additionally, the average £-values were estimated. The concentration dependence of £ and the absolute vlaues for £ were compared with structural information obtained from rheological experiments performed on hyaluronic acid solutions. Even though accurate results were found for the concentration dependence of £, there was a semiquantitative relation between the £-values estimated from the diffusion experiments and the rheological experiments.

Effects of stress on electrical transport properties of nickel silicide thin layers synthesized by Ni-ion implantation J. Appl. Phys. 92, 3778 (2002); 10.1063/1.1503409 Formation of cobalt silicide spikes in 0.18 μm complementary metal oxide semiconductor process Ni-silicide phase formation with and without a Ti capping layer was studied by sheet resistance, x-ray diffraction and transmission electron microscopy. Ni monosilicide is found to be the stable phase in a temperature range from 400 to 600°C. At lower temperatures the Ni 2 Si phase is found to be present. For temperatures higher than 700°C NiSi is converted into NiSi 2 . Pyramidal NiSi 2 precipitates were found to grow epitaxially along the Si͗111͘ planes for annealing temperatures as low as 310°C. The epitaxial NiSi 2 grains were found to disappear when the annealing temperature is increased. Stress buildup during Ni silicidation was measured in situ and could be correlated to the formation of the different Ni-silicide phases. The stress induced by Ni-monosilicide formation compares favorably to the stress induced by Co disilicide and Ti disilicide. The average silicon consumption required to obtain a certain sheet resistance was found to be 35% lower for Ni monosilicide compared for Co disilicide. It was found that a two-step process is needed to obtain complete conversion to the preferred Ni-monosilicide phase without lateral silicide growth. The sheet resistance of Ni-silicided narrow poly-Si and active area lines was found to be low, even when Ni silicide was formed without a Ti cap. No degradation of the Ni silicide on the narrow poly-Si lines was observed when the silicidation temperature was increased to 600°C. The reverse bias leakage of shallow Ni-silicided and Co-silicided square diodes was compared for varying junction depths and varying silicide thicknesses. For similar junction depth and similar sheet resistance, a lower reverse bias leakage current was obtained for a Ni-silicided junction compared to its Co-silicided counterpart. This may be attributed to the reduced Si consumption of Ni monosilicide compared to Co disilicide.

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The formation of Ni silicides is studied by transmission electron microscopy during in situ heating experiments of 12 nm Ni layers on blanket silicon, or in patterned structures covered with a thin chemical oxide. It is shown that the first phase formed is the NiSi 2 which grows epitaxially in pyramidal crystals. The formation of NiSi occurs quite abruptly around 400°C when a monosilicide layer covers the disilicide grains and the silicon in between. The NiSi phase remains stable up to 800°C, at which temperature the layer finally fully transforms to NiSi 2. The monosilicide grains show different epitaxial relationships with the Si substrate. Ni 2 Si is never observed.

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Abstract-We present the data on specific silicide-to-silicon contact resistance (ρ c ) obtained using optimized transmission-line model structures, processed for a broad range of various n-and p-type Si doping levels, with NiSi and PtSi as the silicides. These structures, despite being attractive candidates for embedding in the CMOS processes, have not been used for NiSi, which is the material of choice in modern technologies. In addition, no database for NiSi-silicon contact resistance exists, particularly for a broad range of doping levels. This letter provides such a database, using PtSi extensively studied earlier as a reference.

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