P. N. T. Van Velzen

The structures of C2H4O+ ions: Evidence suggesting the occurrence of radiative relaxation of vibrationally excited ethylene oxide molecular ions

Abstract C 2 H 4 O + ions from various sources have been studied by photodissociation in an ICR spectrometer. Molecular ions of ethylene oxide ring open directly after ionization. The radiative relaxation lifetime of the resulting vibrationally excited ions is ≈ 350 ms. Similar effects are observed for the C 2 H 4 O + ions from 1,3-dioxolan.

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.

The relation between lift‐off of photoresist and the surface coverage of trimethylsiloxy groups on silicon wafers: A quantitative time‐of‐flight secondary ion mass spectrometry and contact angle study

In this paper the interaction between a trimethylsilylated silicon substrate and diazonaphthoquinone–novolak photoresist material has been examined. Time‐of‐flight secondary ion mass spectrometry (TOF SIMS) and contact angle measurements of water have been used to determine the surface coverage of trimethylsiloxy (TMS) groups on cleaned and subsequently treated silicon wafers. A linear relation is obtained between the relative surface coverage as measured by TOF SIMS and the cosine value of the contact angle. The surface coverage of the TMS groups has to exceed a value of about 50% of a monomolecular layer to assure the absence of lift‐off of photoresist. Contrary to the common belief that trimethylsilylation of silicon substrates improves the adhesion between photoresist and the silicon substrate, it rather deteriorates the adhesion. This is further corroborated by experiments on silica particles. It is proposed that the low‐surface energy of the trimethylsilylated surface prevents the penetration of the...

The kinetics of a surface-chemical reaction: A time-of-flight secondary ion mass spectrometry study

Abstract Time-of-flight secondary ion mass spectrometry, in combination with neutron activation analysis, has been used to study the kinetics of a surface-chemical reaction, namely the bromomethyldimethylsilylation of oxidized silicon wafers at room temperature in toluene. The anticipated quasi-first-order kinetics are not observed over the entire surface-coverage range. Instead, the apparent rate constant of this “two-dimensional” reaction appears to decrease gradually with increasing coverage up to one third of the maximum packing of one monomolecular layer. Two factors that can contribute to this phenomenon are elaborated in detail. From the calculations presented it can be concluded that the presence of two types of hydroxyl sites (geminal versus lone) at the surface can adequately explain the observed kinetics. On the other hand, a description of the steric hindrance by means of a coverage-dependent energy barrier for molecules approaching the surface also yields reasonable results. On the basis of the data available a distinction between these two extremes cannot be made.

Surface Characterization of Particulate Video Tapes by Static SIMS

In this paper detailed analysis of the surface chemical composition of the outermost molecular layers of CrO2 video tapes is presented. To study this complex metal oxide-organic system, the versatile and sensitive surface analytical technique of Time-of-Flight Secondary Ion Mass Spectromerty (TOF-SIMS) has been applied. The positive and negative spectra of the individual components of the magnetic lacquer as well as the spectra of specially prepared tapes are discussed. Conclusions concerning surface composition, mutual interaction of the various components and effects of calendering are drawn from these spectra. A model to explain the effect of calendering on the surface chemical composition is presented.

Surface science letterAn IETS study of the silylation of plasma aluminium oxide with four trimethylsilylamines and hexamethyldisiloxane

Abstract Inelastic electron tunnelling spectroscopy (IETS) has been applied to study the reaction of four trimethylsilylamines and hexamethyldisiloxane with plasma-grown aluminium oxide. From the spectra it is concluded that both the silylamines and the disiloxane undergo dissociative adsorption onto the oxide surface, resulting in a monolayer coverage of chemically bonded trimethylsilyl groups. Only for the case of trimethylsilylimidazole is residual adsorption of the product amine observed.