The structure and orientation within prototype self-assembled monolayers (SAMs) containing aromatic subunits absorbed on Au substrates has been investigated using infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). Several oligophenyl(di)thiols, namely biphenylthiol (HS-C6H4-C6H5, BPT), biphenyldithiol (HS-C6H4-C6H4-SH, BPDT), biphenyldimethyldithiol (HS-CH2-C6H4-C6H4-CH2-SH, BPDMT), and terphenyldimethyldithiol (HS-CH2-C6H4-C6H4-C6H4-CH2-SH, TPDMT) have been studied. At least one of these molecules, BPDT, has recently been discussed in connection with the fabrication of a simple electronic device using the aromatic oligophenylthiolate SAM as an active component. Our results reveal that organodithiols with a short oligophenyl backbone, that is, BPDT and BPDMT, do not form well oriented layers but demonstrate that longer backbones, for example, a terphenyl unit, do indeed lead to the formation of SAMs with a high degree of molecular orientation.

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The oxidation behavior of i-A163Cu25Fe12 at 800°C in air was investigated by means of TGA, XRD, SEM and TEM. In the beginning a homogeneous oxide layer is formed by the subsequent growth of metastable γ-Al2O3 and Θ-Al2O3. Nucleation of the thermodynamical stable α-Al2O3 occurs at the interface oxide/quasicrystal. The following growth of α-Al2O3 through the oxide layer leads to the formation of oxide nodules. The high growth rate of the α-Al2O3 can be explained by the incorporation of copper ions. The oxidation resistance of the quasicrystal is insufficient at high temperatures, because no protective oxide layer is formed. The high temperature oxidation behavior of Al-Cu-Fe quasicrystal and the aluminides β-FeAl and β-NiAl is compared regarding the oxidation rate, the oxide phases and the concentration changes in the material due to selective oxidation of aluminum.

We have used thermal desorption spectroscopy to carry out a comparative study of potassium adsorption on Al(111) and on the fivefold Al-Pd-Mn surface. Potassium adsorption on the quasicrystal was found to be different than on Al(111). The potassium monolayer desorbed from fivefold Al-Pd-Mn at lower temperatures than from Al(111). Potassium is known to form a dense monolayer on Al(111), with an ideal coverage of 0.33, but for the monolayer on fivefold Al Pd Mn we find that the saturation coverage is only one twelfth. Disciplines Metallurgy CommentsThis article is from MRS Proceedings 643 (2000) ABSTRACTWe have used thermal desorption spectroscopy to carry out a comparative study of potassium adsorption on Al(111) and on the fivefold Al-Pd-Mn surface. Potassium adsorption on the quasicrystal was found to be different than on Al(111). The potassium monolayer desorbed from fivefold Al-Pd-Mn at lower temperatures than from Al(111). Potassium is known to form a dense monolayer on Al(111), with an ideal coverage of 0.33, but for the monolayer on fivefold Al Pd Mn we find that the saturation coverage is only one twelfth.