Roughness of thin perfluoropolyether lubricant films: influence on disk drive technology

Abstract

Abstract-In disk drive technology, lubricant thickness and roughness are important, but often overlooked, contributors to slider-disk spacing. In this paper, we use X-ray reflectivity to measure the thickness and lubricant-air roughness of a perfluoropolyether lubricant (Fomblin Zdol) on silicon wafers and carbon overcoats. For Zdol on smooth silicon, the roughness increases with increasing lubricant thickness consistent with capillary wave roughening. For Zdol on the rougher surface of amorphous hydrogenated carbon, the lubricant smoothes to a value limited by the capillary wave roughening. We show that the lubricant density above the surface does not reach the density of air until approximately 3 away from the average lubricant thickness. This lubricant-air interface width contributes substantially to current and future slider-disk spacings.

Assessment and Formation Mechanism of Laser-Induced Periodic Surface Structures on Polymer Spin-Coated Films in Real and Reciprocal Space

“…This value of fluence is slightly higher than that corresponding to the experimental threshold for ripple formation for PET and PTT (4 mJ/cm 2 ), but it should be remembered that a simplified temperature calculation was performed. The temperature increase above T g is expected to induce an increase in surface roughness caused by capillary waves, 33 enhancing surface inhomogeneities and facilitating the feedback mechanism involved in LIPSS formation. For PC, as mentioned above, higher fluences and numbers of pulses are needed to induce LIPSSs, as expected due to its higher T g (Table 1).…”

In Situ Monitoring of Laser-Induced Periodic Surface Structures Formation on Polymer Films by Grazing Incidence Small-Angle X-ray Scattering

“…51,52 These random height variations can be envisioned as the superposition of many different Fourier components with different spatial periods. 47,53 In this case the roughness, , is given by:…”

“…The shortest wavelength is of the order of the distance between the atoms or molecules in the liquid and the longest is limited by the attractive interaction with the underlying substrate 53 . Due to the fact that in our case the PTT film at room temperature is below the glass transition temperature T g (44 ºC), the film roughness is then dictated by the complex mechanism of solidification of the liquid solution during spin-coating.…”

Modeling Sliding Contact of Rough Surfaces with Molecularly Thin Lubricants

“…For a discussion on the applicability and limitations of the GW approximation and similar approaches used to model roughness the reader is referred to the extensive literature available on the subject [20][21][22][23][24]. In static measurements of roughness, the sharp AFM tip experiences a meniscus force when brought into proximity with the lubricant layer because of lubricant transfer to the tip [15]; this effect would be larger for thicker films and would affect adhesion. For molecularly thin films, meniscus formation is deemed unfavorable and a Lenard-Jones-type surface potential is used to calculate adhesion; nevertheless, the resulting formulation for the adhesive force on one asperity is equivalent to that of the meniscus force [4,13,14].…”

“…Various effects, such as thermally excited capillary waves [15] and 'lubricant moguls' [16,17], as well as the lubricant thickness itself [18] contribute to the experimentally measured roughness and need to be accounted for within the context of lubricant contact. The ISBL model [3,4] addresses some of these issues by utilizing experimental measurements of roughness under both static and dynamic conditions.…”