Hybrid Lubricant Film With High Bonding Ratio and High Coverage

The frictional properties of a hybrid lubricant film composited from perfluoropolyether (PFPE) lubricant (Moresco DDOH) with single end group and PFPE film deposited from HT170 (Solvay) via photoelectron-assisted chemical vapor deposition (PACVD) were evaluated using a pin-on-disk tester and compared with that of a Z-tetraol dip-coated film. The frictional coefficient of only the HT170 film deposited via PACVD was considerably high; however, the hybrid lubricant film without the mobile fraction showed a friction coefficient equivalent to that of the Z-tetraol film with a mobile fraction of 40%.

TOF-SIMS Analysis of Accumulated PFPE Lubricant Smear Following Laser Heating

The structural and molecular weight changes to lubricant picked up following laser heating in heat-assisted magnetic recording (HAMR) were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The intensity of the ion mass fragments depended on the decomposition pathways and changed drastically, as did the average molecular weight of the picked-up lubricant as heating temperature increased. The fragment series formed by the dissociation of end groups with low molecular weights (CH3O+) showed a high intensity at temperatures under 300 °C, whereas at temperatures over 400 °C, the fragments series formed by the dissociation of the end-group component (C5H9O4F2+) increased. Overall, the results presented herein suggest that the chemical and thermal stability of the hydrocarbon terminal ends of lubricants should be improved in order to decrease depletion of the lubricant film and lubricant pickup by laser heating in HAMR.

Molecular Dynamics Simulation of Ultrathin Perfluoropolyether Lubricant Depletion under Moving Laser Heating

In this work, molecular dynamics simulations of nanostructured perfluoropolyether (PFPE) lubricants were performed to investigate the depletion instability under rapid scanning laser heating. A modified coarse-gained model was utilized to represent the random copolymer structures of PFPEs. In the simulation, only a partial lubricant near the substrate was irradiated by the laser beam to mimic the nano-scale heat transfer from disk to lubricant. During the laser heating, the surface morphological changes of the PFPE lubricant indicated that the lubricant beads initially raise up and diffuse due to thermal expansion, and then evaporate and form circular ridges around the laser beam center, leading to aggravated depletion. Moreover, the lubricant decomposition was subtle and regarded as negligible; while the raised ridges around the depletion area signified that the non-equilibrium thermo-capillary stress plays an important role in lubricant depletion. The surface temperature contour profiles of the lubricant were evaluated as well. It was showed that the increased temperature is centered around the laser beam and quickly decays toward the ambient temperature, forming non-concentric oval shape distributions and ultrahigh lateral thermal gradients. In addition, the maximum temperature (up to 990 K) was also examined and it is consistent with the ones required by HAMR systems to achieve areal densities beyond 1 Tb/in2.