Paul H. Kasai

Degradation of perfluoropolyethers Catalyzed by Aluminum Oxide

Thermal stabilities of perfluoropolyethers, Fomblin Z, Fomblin Y, Krytox, and Demnum in the presence of Al2O3 were examined. Fomblin Z was found to degrade at 200°C in two stages, the slow first stage, and the vigorous second stage leading to complete loss of fluid. It is concluded that oxide-to-halide conversion occurs on Al2O3 surface during the first stage. The second stage is attributed to a catalytic process induced by Lewis acid AlF3. Based on NMR and mass spectroscopic evidences the following reaction mechanism is advanced for the second stage: (1) a bidentate linkage is formed between an acidic aluminum and two oxygen atoms of an acetal unit (-O-CF2-O-) of Fomblin Z chains, and (2) the partial positive charge thus developed at the acetal carbon induces a fluorine atom transfer from the adjacent CF2 unit onto the acetal carbon and results in chain scission with transformation of the acetal sector into a methoxy end-group (-O-CF3) and the adjacent unit into either an acylfluoride end-group (FCO-CF2-), or a fluoroformate end-group (FCO-O-CF2-). Lacking acetal units Krytox and Demnum are stable against this degradation process. In the case of Fomblin Y, owing to the paucity of acetal units, no reaction was observed when heated in the presence of Al2O3; when heated with AlCl3, removal of acetal units and consequential formation of functional end-groups were observed.

Copper carbonyls, Cu(CO) and Cu(CO)3: matrix isolation ESR study

Determination des facteurs g et des tenseurs de couplage hyperfin des noyaux Cu et 13 C. Interaction quadripolaire du noyau Cu dans le cas de Cu(CO) 3 . Liaison dative σ entre doublet libre de CO et orbitale (s) sp hybride (s) vacante (s) de Cu et retrodonation π de Cu vers les orbitales π* vacantes de CO

Carbon Overcoat: Structure and Bonding of Z-DOL

Carbon films (∼100 Å thick) sputter-deposited on silicon coupons were examined by ESR. Based on the results obtained and conclusions reported earlier in the literature, it is concluded that sputter-deposited carbon films are best described as stacks of closely packed spheroidal granules with diametric dimension of several nanometers. Individual granules would have either the graphitelike or diamondlike bonding scheme, and dangling bonds are hosted in the diamondlike granules. Z-DOL bonding occurs when a hydrogen atom is transferred from the hydroxyl group of Z-DOL to a dangling bond. The effect of exposing freshly prepared carbon film to Z-DOL vapor without prior exposure to air, the effect of argon pressure during sputtering, the effect of discharge current, and the effect of hydrogen or nitrogen in the discharging media (argon) are discussed and/or analyzed in terms of the granular structural model.

Z-DOL and carbon overcoat: bonding mechanism

It has been postulated earlier that the bonding between Z-DOL and sputtered carbon occurs when a hydrogen atom is transferred from a hydroxyl end of Z-DOL to a dangling bond site shielded inside the sp/sup 3/ (diamondlike) granules of the carbon film, and the Z-DOL moiety is linked to the carbon as an alkoxyl group, HO-CH/sub 2/-CF/sub 2/-O-(-CF/sub 2/-CF/sub 2/-O-)/sub m/-(-CF/sub 2/-O-)/sub n/-CF/sub 2/-CH/sub 2/ -O-[carbon]. The postulated mechanism predicts that the Z-DOL bonding should occur spontaneously if freshly sputtered carbon were exposed to Z-DOL molecules without prior exposure to air, and that, for disks lubricated with Z-DOL, there would be less hydroxyl hydrogens, and there would exist the alkoxyl units depicted above. A recent reported result on vacuum deposition of Z-DOL (without prior exposure to air) clearly revealed the predicted spontaneous bonding, and analyzes by TOF-SIMS of disks lubricated with Z-DOL demonstrated the predicted decrease of the hydroxyl hydrogen and emergence of the predicted alkoxyl units as the bonding fraction of Z-DOL increases.

Microstructure and properties of ultrathin amorphous silicon nitride protective coating

The effect of N content on the structure and properties of rf reactively sputtered amorphous silicon nitride (a-SiNx) has been studied by Rutherford backscattering spectrometry, x-ray reflectivity, ellipsometry, and nano-indentation. The N content in the film increased with the N2 concentration in the sputtering gas until the Si3N4 stoichiometry was reached. The hardness of a-SiNx increased with density, which in turn increased with the N content. The maximum hardness of 25 GPa and density of 3.2 g/cm3 were attained at the stoichiometric Si3N4 composition. With the application of a protective overcoat for magnetic disks in mind, thin a-SiNx films were deposited on CoPtCr media to examine their coverage, pinhole density, and wear resistance. According to x-ray photoelectron spectroscopy, the minimum thickness of a-SiNx required to protect the CoPtCr alloy from oxidation was 10 A, which was 10 A thinner than that of the reference amorphous nitrogenated carbon (a-CNx). A statistic model showed this lower thi...

Effect of N doping on structure and properties of DLC films produced by plasma beam deposition

A novel plasma beam source for the deposition of DLC films is described. Wide ranges of ion energy (130-250 eV) and C/sub 2/H/sub 2//N/sub 2/ flow conditions have been used to investigate the effect of N doping an the structure and properties of DLC films. The resulting films are characterized by their chemical composition, Raman spectra, electron spin density, mass density, and hardness, which critically depend on the N content. The addition of N causes the sp/sup 2/ carbon content in the DLC films to increase and results in lower density and hardness. The film density also decreases with increasing ion energy at high N concentrations. Carbon films with maximum density and hardness of 2.1 g/cm/sup 3/ and 25 GPa, respectively, can be produced using the plasma beam source.

Acid generation and acid diffusion in photoresist films

Triarylsulfonium salts have been widely used as acid photogenerators in chemically amplified photoresists. A technique was developed for measuring the amount of acid which is generated on irradiation of polymer films containing sulfonium salts and the results of these measurements were used to obtain an understanding of the importance of acid chemistry on the lithographic performance of acid-catalyzed resists. The results from both electron beam and ultraviolet irradiations suggest that polarity effects are very important factors in determining the efficiency of acid generation. The effect of sulfonium salt loading percentage on acid generating efficiency was also studied. Thermal analysis of polymer films containing sulfonium salts has shown greater plasticization effects for sulfonium salts in polar polymer films indicating that the interaction between sulfonium salts and polymers is better for polar polymers. ESR experiments have determined the nature of the radicals which are produced following irradiation and these results suggest a mechanistic understanding of the polymer structural effects. In the case of acid-sensitive polymers, it has been possible to determine the extent of acid-catalyzed chemistry which, in turn, provides a means of estimating the acid diffusion range in this polymer film.

Perfluoropolyethers with Dialkylamine End Groups: Ultrastable Lubricant for Magnetic Disk Application

It has been shown earlier that addition of X1P (partially fluorinated hexaphenoxy cyclotriphosphazene) to the lubricant Z-DOL markedly increases the durability of the magnetic disk system. Its efficacy has been attributed to the strong nucleophilic property of the triphosphazene ring. It follows that perfluoropolyethers terminated with nucleophilic end groups should exhibit a durability comparable to that of the Z-DOL/X1P mixture. To this end perfluoropolyethers with dialkylamine end groups were conceived and synthesized as better alternatives to Z-DOL or to the Z-DOL/X1P mixed system. Examination of the newly synthesized lubricant revealed that (1) perfluoropolyethers with dialkylamine end groups are resistant to the degradation process catalyzed by Lewis acid (e.g., aluminum oxide), (2) disks lubricated with these lubes have durability significantly better than those lubricated with Z-DOL, (3) in the drive system with disks lubricated with these lubes, the issue of the silicon oxide formation from siloxane contaminant is effectively contained (owing to the absence of degraded lube), and (4) the HDI system with disks lubricated with these lubes performs well even in the most aggressive atmospheric condition, i.e., nitrogen with 0% relative humidity.

Degradation of Disk Lubricant: Ramification in Disk Drives and Direct Detection by TOF-SIMS

The degradation of Z-dol catalyzed by Lewis acid centers on the slider surface leads to chain scission forming one type of fragment terminated with a fluorocarbonyl end-group and the other with a trifluoromethoxy end-group. The former, in contact with humid air, converts to a fluorinated carboxylic acid Z-COOH. Z-COOH is an excellent scavenger for alkali or alkaline earth metal ions. Z-COO-M+ thus formed is a strong surfactant, and, in a humid environment, forms microdroplets embodying water in the core. Metal ions thus scavenged on a disk surface can be readily detected by TOF-SIMS, and the microdroplets by optical microscopy in the dark-field mode. The presence of fragments having a trifluoromethoxy end-group on the disk surface can also be established by TOM-SIMS. A careful intensity analysis of peaks due to anions having a trifluoromethoxy end-group permits a semi-quantitative assessment of the extent of degradation. The study has also shown that degradation is caused by such production processes as tape-polishing and by such disk drive operations as the head flying over a single track or over a band in a seek-mode.

MAS-NMR spectroscopic study of water in zeolites

Abstract Using the magic-angle spinning technique, ‘high-resolution’ proton NMR spectra of water in fully hydrated zeolites have been examined. The chemical shift of water was noted to vary in correlation with the Si/Al ratio. The variation is shown to reflect the composite effect of the disruption of hydrogen bonding between water molecules, and the interaction of water molecules with the lattice oxygen. The study also showed that the interparticle diffusion occurs at ambient temperature, while the intraparticle diffusion depends on the number and size of the cations. For highly siliceous zeolites (ZSM-5 and silicalite), it was shown that, while water molecules are located interstitially in ZSM-5, they are located on the extracrystalline surface of silicalite. The study has also demonstrated that water molecules in ZSM-5 zeolite are driven out of crystals by polar organic molecules, but not by non-polar organic molecules.