The potential dependent structure change and mass transport at an 11-ferrocenyl-1-undecanethiol (FcC 11 SH) self-assembled monolayer on a gold electrode with various coverages were investigated by simultaneous Fourier transform infrared reÑection absorption spectroscopy (IRRAS) and electrochemical quartz crystal microbalance (EQCM) measurements in 0.1 M solution. As soon as the terminal ferrocene group was HClO 4 oxidized to a ferricenium cation (Fc`), a number of upward and downward IRRAS bands were observed and the surface mass was increased. The intensity of the IRRAS bands corresponded well with the mass change. This behavior is attributed to the redox reaction induced orientation change in the monolayer and FcC 11 SH ion pair formation between the Fc`cation and the perchlorate anion in solution. The monolayer FcC 11 SH with a lower coverage was less stable and was decomposed at a less positive potential than that with a high coverage. Models are proposed to explain the coverage dependent behavior of the monolayer FcC 11 SH induced by the redox reaction of the terminal ferrocene moiety.

The electrochemical deposition of platinum on an Au(111) single-crystal electrode in acidic solutions containing H 2 PtCl 6 was studied using an electrochemical scanning tunneling microscope (STM) and electrochemical quartz crystal microbalance (EQCM). The STM investigation showed an ordered adlayer of PtCl 6 2-on the electrode surface during the electrochemical deposition of platinum and a Pt(111)-(1×1) structure on the electrode surface after the electrode was rinsed with a Pt complex-free solution. Formations of the Pt(111) bulk phase and surface structure of Pt (111)- (1×1) were confirmed by X-ray diffraction (XRD) and the underpotential deposition of copper and hydrogen, respectively.

The potential dependent structural change and irreversible anodic decomposition of the self-assembled monolayers of 3-mercaptopropanenitrile (HSC2CN) and of 8-mercaptooctanenitrile (HSC7CN) on gold electrode were investigated by two modes of electrochemically modulated infrared spectroscopy, namely, the subtractively normalized interfacial Fourier transform infrared reflection-absorption spectroscopy (SNIFTIRS) and the difference spectra with only one potential alteration. In addition to the bands due to water molecules around 3100-3500 cm -1 and 1600-1700 cm -1 , bands were observed around 2930, 2850, 2342, and 2250 cm -1 at both the HSC7CN and HSC2CN modified gold electrodes. Except for the band at 2342 cm -1 , all the bands were observed only by using p-polarized light, suggesting these bands are due to adsorbed species. The 2930 and 2850 cm -1 bands are of the asymmetric and symmetric C-H stretching modes of methylene groups, respectively. The intensities of these two bands decreased a little as potential became more positive. These results suggest that the alkyl chain stands closer to surface normal when potential became more positive. The peak position of the 2250 cm -1 band shifted slightly to lower frequency than that of the same band in neat liquid of corresponding mercaptoalkanenitrile and was not affected by potential so much. On the basis of these results the 2250 cm -1 band was assigned as the CN stretching mode of the terminal CN group, which has no direct interaction with gold. The fact that the absorbance decreased as potential became more positive suggests that the orientation of the terminal nitrile group became closer to parallel to the surface. The 2342 cm -1 band is due to CO2 in solution generated by an irreversible oxidative decomposition of monolayer as this band was observed even by using s-polarized light and grew in the potential region where anodic current flowed. The irreversible anodic decomposition of the monolayer in positive potential region was confirmed by XPS measurements. Effects of alkyl chain length on both the potential dependence of peak position and intensity and the nature of anodic oxidation were also discussed.

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Grain size distributions and average grain sizes in the longitudinal direction of the Cu interconnect in 50-, 70-and 80-nm-wide Cu interconnects were evaluated and compared with the resistivities of each interconnect. After annealing, the standard deviation of grain sizes for 50-nm Cu interconnect increased to 27.5, and the average grain size microstructure grew to larger than that of as-deposited 50-nm Cu interconnects. The value of standard deviation of grain sizes in the normal distribution histogram for a 50-nm wire was found to be much smaller than those for 70-and 80-nm Cu wires after annealing. This implies that adequate grain growth should not be expected in the very narrow Cu interconnects (less than 50-nm) of the future if they are made with the conventional annealing process.