Interaction of Alcohols and Ethers with a-CF_x Films

Abstract

The surfaces of the magnetic data storage hard disks used in computers are coated with a thin film of amorphous carbon and a layer of perfluoropolyalkyl ether (PFPE) lubricant. Both protect the surface of the magnetic layer from contact with the read-write head flying over the disk surface. Although the most commonly used carbon films are amorphous hydrogenated carbon, a-CH(x), it has been suggested that the thermal properties of amorphous fluorinated carbon films, a-CF(x), might be superior. This work has probed the interaction of small fluorinated ethers and alcohols with the surfaces of a-CF(x) films to understand the effects of carbon film fluorination on the interaction of the lubricant with its surface. Temperature-programmed desorption was used to measure the desorption energies of small fluorocarbons from the a-CF(x) surface and to compare their desorption energies with those from the surfaces of a-CH(x) films. These measurements reveal that, similarly to a-CH(x) films, a-CF(x) films expose a heterogeneous surface on which fluorocarbons adsorb at sites with a range of binding energies. The fluorocarbon ethers all have lower heats of adsorption than their hydrocarbon counterparts, suggesting that the ethers adsorb by donation of electron density from the oxygen lone-pair electrons to sites on the surface. Fluorinated alcohols have roughly the same heats of adsorption as their hydrocarbon counterparts. There is little significant difference between the interactions of fluorinated ethers (or alcohols) with the surfaces of either a-CF(x) or a-CH(x) films.

Vibrational and Photoelectron Investigation of Amorphous Fluorinated Carbon Films

“…added to carbon allotropes can furthermore have a critical influence on the structures and properties of carbon-based materials, leading to a variety of one- to three-dimensional structures. In this respect fluorinated amorphous carbon (a-C:F) is one of the most promising materials for interlevel dielectric films due to its low dielectric constant (lower than silicon). − Most studies suggest wide potential applications of the a-C:F thin films due to the improvements achieved with respect to carbon films in the nonwetting and mechanical properties, , not far from those of polytetrafluoroethylene (PTFE). Partially or totally fluorinated carbon films have been produced in a variety of ways, from radio frequency plasma deposition to plasma enhanced or hot-wire chemical vapor deposition − and magnetron sputtering …”

Vacuum vapor deposition of PFPE molecules on CHxNy and CHxFy amorphous carbon surfaces

“…Therefore, the increase in the bonded fraction will be caused by the change in the number of dangling bonds induced by doping F into the film (Lim et al 2006), i.e., it will be based on the increase in the doping F, at first, the CF and CF 2 portions increase (C=C portions remain), then the CF and CF 2 portions decrease and the CF 3 portions increase (C=C portions decrease). Although this description is similar to the case of the CHx film and is reasonable, the nature of the bonding mechanism is unclear, therefore, further research is necessary for confirmation of the bonding mechanism because it depends on several complex factors such as the polar factor, resonance factor, steric factor, and hybrid orbital.…”

Effect of Heat Treatment Temperature on PFPE Molecules Bonded on DLC Surface

“…For vacuum vapor deposition, the PFPE film can be lubricated on the DLC surface without exposure to the atmosphere, therefore, contamination from the atmosphere does not affect the adsorption between the PFPE molecules and the active sites of the DLC surface during the lubrication process. On the other hand, in the traditional dip-coating method for PFPE lubrication, the heat treatment process can effectively increase the thickness of the bonded layer of the PFPE film [6][7][8][9][10][11] . In this study, the PFPE bonded layer is formed on the DLC surface as a function of the heat treatment time by the dip-coating method and compared to that by the vacuum vapor deposition method.…”