Comparative Surface Study on Silicon Dioxide Film Covered with Alcohols

Abstract

We investigated the relative coverage of an alcohol adsorbed on silicon dioxide (SiO2) film by angle resolved X-ray photoelectron spectroscopy (ARXPS). We found that both Si 2p (103.3 eV; Si-O) and O 1s (532.5 eV; Si-O) spectra decreased in order of IPA > ethanol > methanol through all takeoff angles. In addition, both spectra decreased as the takeoff angle decreased in these alcohol treatments. The C 1s (284.6 eV; C-H) spectrum increased in order of IPA < ethanol < methanol through all takeoff angles, and increased as the takeoff angle decreased. Both Si 2p and O 1s signal intensities could be affected by the amount of carbon on the surface during takeoff of the X-ray. We hypothesize that alcohols are adsorbed on the outermost surface of SiO2 film and that the surface may be sufficiently covered with methyl groups or methanol. However, the surface is not completely covered with ethyl groups or propyl groups. The relative coverage of alcohols adsorbed on the SiO2 film in addition to their water contact angles are discussed in greater detail.

Comparative Surface Study on Hydrogen Terminated Si Surface Covered with Alcohols

“…In other words, methanol can easily adsorb to the SiO 2 surface compared to IPA or ethanol. 31 Note: the treatment time is quite different in between alcohol dipping (10 min) and water rinse (several second). In addition, it was observed that there is a different wettability in between water and alcohols onto the H-terminated surface.…”

“…XPS detected O1s signal from the bulk thermal SiO 2 10 nm. 31 Comparison of the C 1s /Si 2p ratio on the H-terminated Si and SiO 2 surfaces.-A comparison of the C 1s /Si 2p ratio on the H-terminated Si and SiO 2 surfaces is shown in Figure 8. Analysis of SiO 2 surfaces is described in detail in a previous study, 31 and the alcohol coatings on the SiO 2 surfaces in that study were performed in the same manner as this study.…”

“…We previously reported that the relative coverage of an alcohol adsorbed on silicon dioxide (SiO 2 ) film by angle resolved X-ray photoelectron spectroscopy (ARXPS). 31 Both Si 2p (103.3 eV; Si-O) and O 1s (532.5 eV; Si-O) spectra decreased in the order of IPA > ethanol > methanol through all takeoff angles. In addition, both spectra decreased as the takeoff angle decreased in these alcohol treatments.…”

“…The C1s /Si 2p ratios on the SiO 2 surface were referred to the previous study 31. Note: the ratio of Si 2p Si-Si signal intensity for H-terminated Si surface to SiO 2 surface was approximately 5 to 4. )…”

“…The WCA on the SiO 2 surface increased in order of methanol, ethanol, and IPA, since an alcohol with a high carbon number can increase the distance between the surface (polar molecule: oxygen of SiO 2 as well as OH groups) and a water droplet (polar molecule). 31 The adsorption states on an H-terminated Si surface require further detailed clarification, and therefore in this study we used ARXPS to compare the relative coverage of methanol, ethanol, and IPA adsorbed on the surface. We also discuss the relationship between their coverage and WCA, and compare the relative coverage to previous data obtained from SiO 2 film surfaces.…”