Characterization of PTFE on Silicon Wafer Tribological Transfer Films by XPS, Imaging XPS and AFM

Beamson, G.; Clark, D. T.; Deegan, David; Hayes, Neil W.; Law, Derek; Rasmusson, Johan; Salaneck, W. R.

doi:10.1002/(sici)1096-9918(199603)24:3<204::aid-sia90>3.0.co;2-c

Cited by 34 publications

(18 citation statements)

References 18 publications

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“…It has been well established that under slow (< 10 mm Á s À1 ) sliding speeds, the transfer of PTFE can provide an aligned, thin, transfer film for low shear sliding. [85][86][87][88][89] The relationship between transfer film thickness and wear rate suggests that extremely thin and uniform films of PTFE might also be very wear resistant. Recently, experiments were conducted to quantify the tribological properties of model PTFE films to test the hypothesis that thin aligned PTFE films can support low wear sliding.…”

Section: Quantifying Transfer Filmsmentioning

confidence: 99%

Polymeric Nanocomposites for Tribological Applications

Burris

Boesl

Bourne

et al. 2007

Macro Materials & Eng

237

120

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Composites in TribologyPolymer composites are well known for offering engineers high strength-to-weight ratios and flexibility in material design. [1,2] The physical properties of a composite can be tuned to satisfy various functional requirements of a target application, including stiffness and strength, thermal and electrical transport, and wear resistance to name a few. Often, composites are designed to fulfill several functions simultaneously.One area of engineering that is particularly invested in the development and design of high performance polymer composites is tribology, the science related to interacting surfaces in relative motion. Bearings are systems that contain sliding interfaces, and are relied upon by nearly all moving mechanical systems. Though rarely recognized, Feature ArticlePolymer nanocomposites operate in applications where fluid and grease lubricants fail, and have superior tribological performance to traditional polymer composites. Nanoparticle fillers have been a part of notable reductions in the wear rate of the polymer matrix at very low loadings. Despite instances of remarkable wear reductions at unprecedented loadings (3 000 times at 0.5% loading in one case), there is a lack of general agreement within the literature on the mechanisms of wear resistance in these nanocomposites. In addition, results appear to vary widely from study to study with only subtle changes of the filler material or blending technique. The apparent wide variation in tribological results is likely a result of processing and experimental differences. Tribology is inherently complex with no governing laws for dry sliding friction or wear, and the state of the art in polymeric nanocomposites tribology includes many qualitative descriptors of important system parameters, such as particle dispersion, bulk mechanical properties, debris morphology, and transfer film adhesion, morphology, composition, and chemistry. The coupling of inherent tribological complexities with the complicated mechanics of poorly characterized nanocomposites makes interpretation of experimental results and the state of the field extremely difficult. This paper reviews the state of the art in polymeric nanocomposites tribology and highlights the need for more quantitative studies. Examples of such quantitative measurements are given from recent studies, which mostly involve investigation of polytetrafluoroethylene matrix nanocomposites.

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Section: Quantifying Transfer Filmsmentioning

confidence: 99%

Polymeric Nanocomposites for Tribological Applications

Burris

Boesl

Bourne

et al. 2007

Macro Materials & Eng

237

120

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“…[5][6][7][8][9][10][11][12][13] AFM is especially suited to polymer analysis due to the low applied forces in contact mode, which can be further reduced by using tapping mode. These low forces allow the film surface to be imaged without modification by the force of the AFM tip on the surface.…”

Section: Introductionmentioning

confidence: 99%

Surface morphology of PECVD fluorocarbon thin films from hexafluoropropylene oxide, 1,1,2,2-tetrafluoroethane, and difluoromethane

Labelle

Gleason

1999

J. Appl. Polym. Sci.

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Atomic force microscopy (AFM) measurements have been made on a series of fluorocarbon films deposited from pulsed plasmas of hexafluoropropylene oxide (HFPO), 1,1,2,2-tetrafluoroethane (C 2 H 2 F 4 ), and difluoromethane (CH 2 F 2 ). All of the films give images showing nodular growth (cauliflower-like appearance), with the size and distribution of the nodules dependent on both the precursor, the degree of surface modification to which the growing film is exposed, and the substrate surface. Films deposited from C 2 H 2 F 4 showed clusters of smaller nodules around larger nodules, whereas films deposited from CH 2 F 2 were characterized by a uniform distribution of smaller nodules, and films deposited from HFPO had the largest observed nodules. Movchan and Demchishin's structure zone model was applied to the observed films, which were all found to be zone 1 structures, indicating that film growth is dominated by shadowing effects. Increased substrate temperature and incident power per nm of film deposited results in decreased rms roughness, consistent with greater atomic mobility during deposition. Larger nodules in the fluorocarbon films developed on silicon wafer substrates than on rougher Al-coated substrates. Advancing contact angles for all of the films were found to be higher than that of PTFE (108°), indicating both hydrophobic and rough surfaces. Specifically, contact angles of films deposited from HFPO were found to increase with pulse off-time, the same trend observed for both the CF 2 fraction of the film and the rms roughness.

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“…1 Identification of the physical and chemical nature of these interactions has been of great academic as well as commercial importance for more than 5 decades. [1][2][3][4][5][6][7][8][9][10][11][12] Makinson and Tabor studied the transfer and friction of polytetrafluoroethylene (PTFE) sliding on glass using optical and scanning electron microscopic techniques, where they demonstrated that PTFE could be transferred onto other surfaces during sliding motion. 1 They also identified two frictional regimes (low and high) depending on both the temperature at which the sliding was carried out and the speed of the sliding motion.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10] Although many other studies on PTFE transfer to another solid surface have been published, most have focused on improvement of the physical properties of surfaces, i.e., achieving lower friction coefficients and wear rates. [11][12][13][14][15][16][17][18][19] However, the nature of those interactions at the atomic scale has not been completely understood. To this end, applying computational chemistry methods as a tool for analyzing the mechanism of friction and transfer film formation has recently been reported.…”

Section: Introductionmentioning

confidence: 99%

Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

Uçar

Çopuroğlu

Baykara

et al. 2014

The Journal of Chemical Physics

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We investigated the tribological interaction between polytetrafluoroethylene (PTFE) and silicon oxide surfaces. A simple rig was designed to bring about a friction between the surfaces via sliding a piece of PTFE on a thermally oxidized silicon wafer specimen. A very mild inclination (∼0.5°) along the sliding motion was also employed in order to monitor the tribological interaction in a gradual manner as a function of increasing contact force. Additionally, some patterns were sketched on the silicon oxide surface using the PTFE tip to investigate changes produced in the hydrophobicity of the surface, where the approximate water contact angle was 45° before the transfer. The nature of the transferred materials was characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS results revealed that PTFE was faithfully transferred onto the silicon oxide surface upon even at the slightest contact and SEM images demonstrated that stable morphological changes could be imparted onto the surface. The minimum apparent contact pressure to realize the PTFE transfer is estimated as 5 kPa, much lower than reported previously. Stability of the patterns imparted towards many chemical washing processes lead us to postulate that the interaction is most likely to be chemical. Contact angle measurements, which were carried out to characterize and monitor the hydrophobicity of the silicon oxide surface, showed that upon PTFE transfer the hydrophobicity of the SiO2 surface could be significantly enhanced, which might also depend upon the pattern sketched onto the surface. Contact angle values above 100° were obtained.

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Characterization of PTFE on Silicon Wafer Tribological Transfer Films by XPS, Imaging XPS and AFM

Cited by 34 publications

References 18 publications

Polymeric Nanocomposites for Tribological Applications

Polymeric Nanocomposites for Tribological Applications

Surface morphology of PECVD fluorocarbon thin films from hexafluoropropylene oxide, 1,1,2,2-tetrafluoroethane, and difluoromethane

Tribological interaction between polytetrafluoroethylene and silicon oxide surfaces

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