Spreading characteristics of thin liquid films of perfluoropolyalkylethers on solid surfaces. Effects of chain-end functionality and humidity

Min, Byoung‐Chul; Choi, Jeong Woo; Brown, Hugh R.; Yoon, Do Y.; O’Connor, Teresa; Jhon, Myung S.

doi:10.1007/bf00209777

Cited by 80 publications

(53 citation statements)

References 3 publications

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“…In other words, the interaction between the lubricant molecules and the hard disk surface is much stronger than that between the lubricant molecules themselves, and the nonfunctional lubricant film of PFPE Z25 has a layered structure on the hard disk surface. This is a quite different finding from that in the diffusion experiment where the nonfunctional lubricant does not show a layered structure [4][5][6][7]. The mechanism for the difference is not clear, but the difference in the flow rate of lubricant between the diffusion and the spin-off may be one of possible explanations for the same.…”

Section: Resultscontrasting

confidence: 67%

“…It is found that the end group of PFPE molecules has a determinant effect on the film structure. Lubricants with functional end groups, such as Zdol (terminated with hydroxyl groups) [4][5][6], Ztetraol (propylene glycol) [6], AM2001 (piperonyl) [6], A20H (cyclotriphosphazine) [5], show a layered structure on a solid surface. On the other hand, nonfunctional lubricant of Fomblin Z has no step-like profile in the spreading front, and therefore it is concluded that the film of nonfunctional lubricant is continuous across the thickness and has no layered structure [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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The Rheological Behavior of the Nano-Meter Film of Non-Functional PFPE on Hard Disk Surfaces during Spin-Off

2009

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Spin-off experiments were conducted at different temperatures for a nonfunctional PFPE Z25 film with an initial thickness of 2.4 nm, and comparison with the diffusion experiments was carried out. It is found that PFPE Z25 shows completely different rheological behaviors in spin-off and diffusion. Theoretical model based on the Fick law of diffusion was proposed, which is called the Layer Molecular Dynamic Diffusion (LMDD) model. The proposed model results in a much better agreement with the spin-off experimental results than the continuum theory being used at present. Contrary to the results in the diffusion experiment, the nanometer film of nonfunctional PFPE Z25 also shows a layered structure in the spin-off.

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Section: Resultscontrasting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

The Rheological Behavior of the Nano-Meter Film of Non-Functional PFPE on Hard Disk Surfaces during Spin-Off

2009

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“…It was also found that the probe touchdown occurred earlier as the humidity increased and that the attractive force also increased with the humidity. This may be because the mobile fraction of the lubricant increased with the humidity due to the specific interactions of OH end groups with the water molecules (Min et al 1995), resulting in an early meniscus formation. Figures 8 and 9 indicate the effects of humidity and lubricant film thickness on the adhesive force.…”

Section: Resultsmentioning

confidence: 99%

Effect of humidity on the interactions between probes and ultra-thin liquid lubricant films in an environmentally controlled atomic force microscope

2009

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To achieve a magnetic recording density of 1 Tb/in 2 , the required head-disk spacing is expected to be less than 2-3 nm. However, a critical issue in achieving such an ultra-low spacing is the dynamic instability of the head-disk interface (HDI), that is, the experimentally observed hysteresis of the flying sliders. It is important to clarify the interactive forces between the sliders and disk surfaces in a nanometer HDI. In addition, the adhesive forces between the thermally protruding magnetic head writer pole tip, which exists in the most commercially available recording head, and the lubricant film have also become very important. Therefore, in this study, the interactions between the probes of an environmentally controlled atomic force microscope (AFM) and ultra-thin liquid lubricant films were studied as a model experiment, resulting in the acquisition of fundamental knowledge related to the adhesive forces as well as the slider hysteresis. Subsequently, the effect of humidity on the force curve characteristics was investigated by varying the lubricant film thickness. As a result, it was found that the probe touchdown occurred earlier as the humidity increased, with its driving force suggested to be the force of the lubricant meniscus formed on the AFM probe. The probe touchdown occurred earlier for lubricants with a higher mobility. The adhesive force gradually increased with the humidity and was at its minimum for a one monolayer film thickness, independent of the lubricant materials. On the other hand, the elongation of the lubricant meniscus increased with the humidity. Therefore, the probe takeoff occurred later as the humidity increased. Accordingly, the hysteresis increased with the humidity and was mainly dependent on the elongation of the meniscus.

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“…Typical SME thickness profiles for monodisperse Z and Zdol, as analyzed by O'Connor et al [6,7], are shown in figure 1 (a) and (b). As the film spreads with time, the spreading front travels along the surface of the silicon wafers.…”

Section: Scanning Microellipsometrymentioning

confidence: 98%

“…He found that the surface diffusion coefficient increased as the film thickness decreased down to 1 nm and remained constant below that thickness. Subsequent investigations focused on the effects of initial film thickness, endgroup functionality, molecular weight, relative humidity, and temperature for silica surfaces were performed by Min et al [6] and O'Connor et al [7] and for amorphous carbon surfaces were conducted by Ma et al [8,9].…”

Section: Introductionmentioning

confidence: 99%

Spreading and dewetting in nanoscale lubrication

Karis

Kim

2005

Tribol Lett

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This article critically reviews the fundamental scientific tools, as well as constructs cohesive schemes for potential applications, relevant to the molecularly-thin liquid film technology. Our focus is to understand the nanoscale dynamic behavior of thin lubricant films, relevant to the emerging field of nanotechnology, especially for achieving durability and reliability in the nanoscale devices. Our goal is to present a unified and hybrid description of perfluoropolyether (PFPE) experiment, mesoscopic interpretation, microscopic simulation tools, and molecular design tools available up to now. The experimentation and theory for the physicochemical properties of ultra-thin PFPE films are used to examine liquid film in the sub-monolayer to multilayer regime. Methods for extracting spreading properties from the scanning microellipsometry (SME) for various PFPE/solid surface pairs and the surface rheological characterization of PFPEs are examined. The interrelationships among SME spreading profiles, rheology, surface energy, and tribology, are given. Mesoscopic theories, including thermodynamics of evaporation and flow, stability analysis, microscale mass transfer, and capillary waves are introduced to describe thin PFPE film dynamics. Estimation of thin film viscosity enhancement from vapor pressure suppression by dispersion force is reviewed. The method for experimental derivation of lubricant spreading profiles from contact angles is summarized. The implications of capillary waves, or thermal fluctuations, at the surface of polymeric lubricant films are also discussed. The lattice-based, simple reactive sphere Monte Carlo (MC) technique for examining the fundamentals of PFPE dynamics is illustrated. An off-lattice based bead-spring MC model is also introduced to capture a detailed internal structure of the PFPE molecules, and the molecular dynamics method is implemented for a full-scale nanostructural analysis of PFPE ultra-thin films. By systematically tuning the endgroup strengths of PFPE, we examined the physicochemical properties for thin liquid films of the various PFPE/solid surface pairings. These tools accurately describe the static and dynamic behavior of ultra-thin liquid films consistent with experimental findings and thus are suitable for examining the fundamental mechanisms of lubrication in nanoscale devices. Application of the next generation head-disk interface design in information storage device is briefly considered.

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Spreading characteristics of thin liquid films of perfluoropolyalkylethers on solid surfaces. Effects of chain-end functionality and humidity

Cited by 80 publications

References 3 publications

The Rheological Behavior of the Nano-Meter Film of Non-Functional PFPE on Hard Disk Surfaces during Spin-Off

The Rheological Behavior of the Nano-Meter Film of Non-Functional PFPE on Hard Disk Surfaces during Spin-Off

Effect of humidity on the interactions between probes and ultra-thin liquid lubricant films in an environmentally controlled atomic force microscope

Spreading and dewetting in nanoscale lubrication

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