Contamination of aluminium oxide surfaces in ambient air investigated by FTIR MSR and TOF SIMS. Chemisorption of aliphatic carboxylic acids

Abstract

Contamination in ambient air of freshly evaporated aluminium surfaces covered with a thin layer of native oxide has been studied using Fourier transform infrared multiple specular reflectance (FTIR MSR) and time-of-flight secondary ion mass spectrometry (TOF SIMS). The FTIR MSR experiments yield vibrational spectra than can be attributed to short-chain aliphatic carboxylic acids. Some reference spectra have been measured by FTIR MSR spectroscopy of samples prepared by chemisorption of formic, acetic, lactic, butyric and palmitic acids on oxidized aluminium and (in some cases) silver surfaces. From these data the major contaminant has to be the acetate ion. Saturation of the spectral intensities is observed within an hour after exposure to air. The TOF SIMS spectra confirm the conclusion with respect to the acetate ion. Mass peaks belonging to the formate, lactate and some inorganic anions are present in the TOF SIMS spectra.