Potential-dependent structure and dynamics of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([BMIM][TFSA]) on an Au electrode have been investigated by using surface-enhanced infrared absorption spectroscopy (SEIRAS). In situ, real-time IR measurements during potential scans enable us to probe a hysteretic exchange and reorientation of both the cation and anion at the interface simultaneously owing to the high interface selectivity and sensitivity of SEIRAS. Our experimental results reveal that during potential scans, the ion density in overlayers changes first, and then the exchange of the ions in the first ionic layer occurs to compensate the changes in surface charge.

The emission spectra from the solid-liquid interface irradiated by a pulsed laser were studied. The solid target used in this study was graphite and boron nitride, and the liquid in which the target was immersed was water, benzene, n-hexane, and carbon tetrachloride. The results showed strong continuous spectrum immediately after a pulse shot, whereas after Ϸ100 ns later from the irradiation it was greatly reduced, and instead, the emission from small molecules dominated the spectra. The line spectra of small molecules observed in the later time range indicate the chemical reaction between the ablated species and the species originated from the liquid molecules. The intensity of the continuous spectrum was very prominent compared to what has been observed for solid-gas interfaces. This is due to rapid electron ion recombination or bremsstrahlung due to highly confined interface plasma.

Immersion plating of metals (Ag, Cu, Ni) onto a porous silicon (PS) layer from aqueous and nonaqueous solutions has been studied. The modified PS layers after the immersion plating were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. Fourier transform infrared spectroscopy and scanning electron microscopy were also performed to investigate the structural changes and microstructure of PS samples after the plating process. In both solutions, the deposition of metal oxidizes PS simultaneously to SiO2. The different deposition behaviors are discussed in terms of different rest potentials of PS in these solutions and electrode potential of each metal. Immersion plating in nonaqueous organic solutions shows that a trace of residual water affects the metal deposition. Based on the results obtained, the mechanism of metal deposition is proposed. The metal deposition proceeds by nucleation and growth via the local cell mechanism. It is also found that metal deposition proceeds very differently on Si wafer and PS surfaces. The different deposition behaviors on both surfaces are discussed. © 2002 The Electrochemical Society. All rights reserved.

The oxidation process of porous silicon in wet air at 323 K was investigated by infrared spectroscopy, particularly focusing on the behavior of the stretching vibrations of Si-H. The fine structure of the absorption bands were clarified with help of vibrational analysis by ab initio molecular orbital calculations. Absorption bands at 2150-2300 em i are assigned to the Si-H vibrations due to OSiH3, O2SiH2, and O3SiH in order of increasing frequency, respectively. The presence of H20 causes St-St bond breaking with dissociative adsorption of H20, resulting in an increase in the amount of Si-H species, which is readily oxidized. The bond breaking causes a prominent enhancement of QSiH in the oxidized states. This contrasts with the behavior of the oxidation in dry air where the introduction of oxygen keeps the amount of Si-H species constant in the course of the oxidation and the growth of QSiH2 and OSiH3 in addition to O3SiH.

Infrared spectra of thin films (a few micrometers) of hydrated sodium silicate glasses after heating at temperatures from 100" to 400°C were measured in the spectral region from 400 to 4300 cm-'. Also, Raman spectra of hydrated glasses were measured in the region from 100 to 1400 cm-'. Water molecules in hydrated glasses were classified into three types by the bonding configuration: water molecules interacting with Si-OH groups, nonbridging oxygens, and bridging oxygens. On the basis of the fundamental bands observed here, we calculated the wave numbers of the combination-overtone bands of water molecules and SiOH groups in hydrated glasses. The calculated wave numbers satisfactorily agreed with observed wave numbers in the nearinfrared region. [