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TECHNICAL PAPERS

# Modeling of the Effect of Preferential Texturing on the Interfacial Forces in Sub-$5nm$ Ultralow Flying Head-Disk Interfaces

[+] Author and Article Information
Allison Y. Suh1

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Andreas A. Polycarpou2

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801polycarp@uiuc.edu

1

Currently with Seagate Technology.

2

Corresponding author.

J. Tribol 129(3), 553-561 (Jan 26, 2007) (9 pages) doi:10.1115/1.2736440 History: Received May 21, 2006; Revised January 26, 2007

## Abstract

Preferential surface texturing is expected to significantly improve tribological performance of ultralow flying magnetic storage head-disk interfaces (HDIs) by modifying the roughness and reducing the contact area preferentially, thereby reducing the relevant interfacial forces, such as friction, contact, and adhesive forces. Because of the different etch rates in the titanium carbide (top surface) and alumina (bottom surface) portions of the slider air-bearing surface (ABS), during reactive ion etching the surface heights possess a distinct bimodal distribution. In order to accurately and realistically capture the interfacial phenomena of the ultralow flying HDI with a preferentially textured slider ABS, a probability density function was proposed by linking two different Gaussian asperity distributions. The proposed bimodal asperity distribution was then directly incorporated into a previously developed rough surface contact model to calculate the corresponding interfacial forces. The results were then directly compared to a single Gaussian approximation (ignoring the bimodality) as well as a high-order polynomial curve-fit approximation (encompassing the bimodality). Comparative studies revealed that the proposed bimodal distribution method has a main advantage of being able to resolve the top and bottom asperity contributions separately, which is physically more accurate, and thereby providing interfacial force estimates that are more physically accurate. Other simpler methods, by assuming a single continuous distribution over the entire surface, are not able to isolate the top and bottom asperity distributions and thus are more likely to overestimate the interfacial forces in sub-5 nm flying HDIs.

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## Figures

Figure 1

20μm×20μm AFM roughness image of a preferentially textured slider surface: (a) top view, (b) isometric view, and (c) surface histogram with Gaussian distribution and Pearson curve fit with respect to surface heights

Figure 2

Normalized histogram of a preferentially textured slider (previously shown in (3)) with a single Gaussian and ninth-order polynomial fit over the total surface height distribution, as well as a single Gaussian fit over the top 31% surface heights with zero mean as used in (3)

Figure 3

(a) Bottom surface Gaussian distribution, (b) top surface Gaussian distribution, and (c) combined Gaussian distribution from top and bottom surfaces and single Gaussian distribution from top 31% surface heights (mean=0nm)(3)

Figure 4

Effect of surface distribution on the prediction of (a) friction force versus separation and (b) contact force versus separation

Figure 5

Effect of surface distribution on the prediction of (a) friction force versus separation and (b) friction force versus net normal contact force

Figure 6

Effect of surface distribution on the prediction of real area of contact versus net normal contact force

Figure 7

Effect of surface distribution on the prediction of (a) mean contact pressure versus net normal contact force and (b) mean shear stress versus net normal contact force

Figure 8

Equivalent isotropic rough surface in contact with an infinitely smooth surface (Greenwood-Williamson contact model (18))

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