THERMAL-TREATMENT OF N-ALKANETHIOLATE MONOLAYERS ON GOLD, AS OBSERVEDBY INFRARED-SPECTROSCOPY

In the present work, we have used reflection-absorption infrared spect roscopy (RAIRS) to investigate the temperature behavior of n-alkanethi ols adsorbed on gold substrates. A careful examination of the spectra (frequencies, integrated intensities, and link widths) reveals at leas t two different types of thermally induced disorder as the temperature is increased. These observations are discussed in light of other rece nt studies using complementary techniques. The overall picture that em erges is that an initial stage is characterized by a gradual untilting of the alkyl chain and the appearance of gauche conformational defect s near the surface, and both of these effects are largely reversible. The subsequent nonreversible disordering of the monolayer is character ized by a large number of defects located below the surface. Infrared spectroscopy is particularly well suited for detecting these changes.