| AVS 56th International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS-ThP |
| Session: | Surface Science Poster Session |
| Presenter: | T. Yamada, RIKEN, Japan |
| Authors: | T. Yamada, RIKEN, Japan M. Kawai, The University of Tokyo, Japan |
| Correspondent: | Click to Email |
Passivation of clean Al(111) has been attempted against oxidation in O2 or air at room temperature by various kinds of adlayers prepared on the surface. The goal of this attempt is to block the growth of oxide layer by introducing a covering monolayer or thin multilayer, whose thickness is smaller than 1 nm. Metallic aluminum surfaces stored in air are usually covered with more than a few nm of Al oxide layer, which prevent us from fabrication of nanostructures and nanoparticles of pure metallic Al. If an ultrathin passivation layer, composed of inorganic or organic materials in a controlled manner, can inhibit oxidation of Al substrate, it will help enhancing the accuracy and precision of nano-scale fabrication. This approach was successful in passivating Si wafer surfaces [1]. When a clean Al(111) surface was exposed to pure O2 gas at room temperature, the surface was covered with an amorphous oxide layer observed by low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) [2]. The thickness of oxide layer was calculated from XPS signal intensities, with referring to spectra of a cleaned sapphire (γ-Al2O3) surface. The process of oxide accumulation was once saturated below ~10-1 Torr of O2 pressure, at which the thickness of oxide layer was <0.5 nm. Formation of such oxide layers was blocked with various kinds of thin adlayers, such as fluoride thin layers, alkanethiol monolayers etc., similarly to the formerly reported C60 layer [3]. At O2 pressures higher than 10-1 Torr, another sort of rigorous oxidation process took place. The thickness of oxide layer was approximately proportional to the logarithm of O2 exposure, reaching a few nanometers. Most of the monolayers from small precursor compounds could not block this process of oxidation. This process seems to involve penetration of O atoms deeply into the Al substrate. Practically, it is desirable to inhibit this rigorous process of oxidation. In this talk, we will present our attempts using monolayers including long linear molecules anchored on Al(111). The oxidation process was examined in the air up to the atmospheric pressure, involving O2 and H2O. Some kinds of adlayers on Al(111) were vulnerable in contact with H2O. It is probably important to involve hydrophobic compounds to build a firm, oxidation-resistant monolayer.
[1] T. Yamada et al., J. Electroanal.Chem. 532 (2002) 247, T. Yamada et al., J. Chem. Phys. 121 (2004) 10660.
[2] H. Brune et al., J. Chem. Phys. 99 (1993) 2128, V. Zhukov et al., Surf. Sci. 441 (1999) 251.
[3] A. V. Hamza et al., Surf. Sci. 318 (1994) 368.