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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Coverage and properties of a-SiNx hard disk overcoat

Bing K. Yen, Richard L. White, Robert J. Waltman, C. Mathew Mate, Yoshiaki Sonobe, and Bruno Marchon

J. Appl. Phys. 93, 8704 (2003); http://dx.doi.org/10.1063/1.1543136 (3 pages) | Cited 24 times

Online Publication Date: 9 May 2003

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Amorphous silicon nitride (a-SiNx) overcoats are deposited on magnetic disks by rf-reactive sputtering to study their coverage and properties. According to the x-ray photoelectron spectroscopy analysis, a-SiNx has a low coverage-limit of ∼10 Å compared with that of the reference a-CNx (∼20 Å). The lower coverage-limit of a-SiNx may be attributed to its high density of 3.2 g/cm3, which corresponds to 93% bulk density. By contrast, the density of diamond-like carbon is only 54% that of diamond. This is in agreement with the results of coverage simulation, which reveal that the film coverage thickness decreases by ∼3 Å per 10% increase in the relative density. Compared with 45 Å a-CNx coated disks, 15 Å a-SiNx coated disks have fewer pinhole defects and are more durable in the accelerated flyability test. The superior performance of a-SiNx disk overcoat may be attributed to its dense structure and high hardness (25 GPa). © 2003 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
79.60.Dp Adsorbed layers and thin films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
79.60.Ht Disordered structures
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Surface morphology and molecular conformation for ultrathin lubricant films with functional end groups

Qian Guo, Satoru Izumisawa, David M. Phillips, and Myung S. Jhon

J. Appl. Phys. 93, 8707 (2003); http://dx.doi.org/10.1063/1.1540169 (3 pages) | Cited 30 times

Online Publication Date: 9 May 2003

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Using molecular simulation techniques based on a coarse-grained, bead-spring model, we examined the static and dynamic properties of linear perfluoropolyethers (PFPEs) in a nanoscale lubricant film on a solid wall. The conformation of the PFPEs, as predicted by the anisotropic radius of gyration, exhibits an oblate structure near the wall, but recovers a spherical shape as the distance from the wall increases. The density profile of the functional end groups for the PFPE molecules shows a characteristic oscillation as a function of the distance from the wall, indicating molecular layering. We also used the simulated surface morphology to examine the PFPE film roughness. Our preliminary dynamic simulations indicate that the wall interaction produces an anisotropy in the self-diffusion coefficient. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Pq Friction, lubrication, and wear
66.30.H- Self-diffusion and ionic conduction in nonmetals

Thin CNx overcoats deposited using various sputtering gases

G. Wei, J. Gong, G. Zangari, M. L. Weaver, and J. A. Barnard

J. Appl. Phys. 93, 8710 (2003); http://dx.doi.org/10.1063/1.1558185 (3 pages)

Online Publication Date: 9 May 2003

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This work presents systematic studies of the effect of various sputtering gases (Ar, Kr, and Xe) on the roughness, density, coverage, stress, and nanomechanical properties of CNx thin films. CNx (1–11 nm) was deposited on Si (100) substrates using dc magnetron sputtering. A three-parameter roughness analysis was carried out using atomic force microscopy. Film thickness and density were measured by x-ray reflectivity. Nanoindentation hardness and modulus were measured using a Hysitron TriboScope® nanomechanical system, while stress measurements were performed using a Flexus thin film stress measurement system. The coverage of CNx is assessed using a pinhole-decoration technique. As the mass of the sputtering gases increases, the density and hardness of CNx increases, while the deposition rate, surface roughness, and compressive stress decrease. Using Kr or Xe, a 3-nm-thick dc-sputtered CNx overcoat displaying good coverage is obtained. © 2003 American Institute of Physics.
Show PACS
68.55.-a Thin film structure and morphology
68.60.Bs Mechanical and acoustical properties
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.37.Ps Atomic force microscopy (AFM)
62.20.M- Structural failure of materials
62.20.Qp Friction, tribology, and hardness

Media tribology design to improve flyability at low flying height

Z. F. Li, C. Y. Chen, J. J. Liu, and S. A. Pirzada

J. Appl. Phys. 93, 8713 (2003); http://dx.doi.org/10.1063/1.1557721 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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As the head media separation (HMS) continues to decrease with increasing areal density, maintaining good flyability performance is crucial to ensure the robustness of the head-disk-interface. Carbon wear and lubricant pickup on the slider surface are found to be the main contributors to flyability degradation. The effects of carbon overcoat and lubricant on load/unload flyability were investigated at the near-contact flying height by either reducing the environmental pressure or slowing down the disk rotating speed. Changing lubricant process and X-1P additive amount can affect lubricant pickup. In order to reduce the head wear, a thin layer of softer functional carbon layer was applied on the top of plasma-enhanced chemical vapor deposition carbon. However, carbon and lubricant modification has some limitations on improving flyability as HMS continues to drop. As an alternative approach to minimizing slider pickup at low flying height, landing the head in the laser textured contact-start-stop zone serves the function of cleaning the head and removing head smear. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness

Writing induced nanodeformation and its effects on head-disk clearance

B. Liu and Y. F. Han

J. Appl. Phys. 93, 8716 (2003); http://dx.doi.org/10.1063/1.1558194 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2003

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Further reducing the head-disk spacing down to 3–4 nm will be needed for future extremely high-density magnetic recording systems of areal densities of 800–1000 Gbits/sq2. On the other hand, it is important to not only reduce the head-disk spacing but also retain the stability of the head-disk interface. This article reports an observation of the spacing change caused by thermal induced nanodeformation of the slider body even when writing current and the writing frequency are just within their value range in normal writing operations. Results indicate that the combination of the internal heating generated by writing operation with the cooling effect of the airflow over the air-bearing surface leads to not only local protrusion of the area around the transducer but also the variation of the crown value of the slider and, therefore, the change of the head-disk spacing. A crown deformation model is proposed and the validity of the proposed model is confirmed by both computer modeling and experimental observations. © 2003 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Precision in situ flying height measurement during track seeking process with intersymbol interference compensation

Lei Wan, Zhimin Yuan, and Bo Liu

J. Appl. Phys. 93, 8719 (2003); http://dx.doi.org/10.1063/1.1555854 (3 pages)

Online Publication Date: 9 May 2003

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In order to use the harmonic ratio to measure the flying height with wide usable bands and high signal to noise ratio for ultrahigh density magnetic recording systems, the harmonic selection channel should be made narrow. But intersymbol interference (ISI) could be, therefore, introduced when this setup is used in the track seeking process. As a result, the measurement accuracy deteriorates significantly. Due to the band-limited nature of the harmonic selection channel, a linear equalizer based on the minimum mean-square error algorithm can be adopted to compensate for ISI and the accuracy achievable is 99%. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
02.70.Rr General statistical methods

Self-assembled monolayers on ta-C surfaces: Effect of sp3/sp2 ratio on adsorption rate and friction

Junho Choi and Takahisa Kato

J. Appl. Phys. 93, 8722 (2003); http://dx.doi.org/10.1063/1.1540170 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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Self-assembled monolayers of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS), CF3(CF2)7(CH2)2SiCl3 were deposited on tetrahedral amorphous carbon (ta-C) surfaces by immersion process. The ta-C films were deposited on silicon substrates by using a filtered cathodic arc system and the sp3/sp2 ratios of the ta-C films were controlled by changing the sample bias voltage. In results of the x-ray photoelectron spectroscopy measurements, it was found that the adsorption rate of silane molecules on sample A (whose sp3 content is about 85%) was higher than that of on sample B (whose sp3 content is about 65%). This trend was qualitatively the same as that found for water contact angle measurement. The friction forces of FDTS/sample A and FDTS/sample B measured by lateral force microscope show FDTS/sample A has lower friction value than that of FDTS/sample B. We conclude the following: the density of dangling bonds, which are effective adsorption sites for silane molecules, increases with sp3 content. Consequently, the adsorption rate of silane molecules increases with increasing sp3 content. The friction force decreases with increasing sp3 content of the ta-C film since more of a close-packed self-assembled monolayer can be formed. © 2003 American Institute of Physics.
Show PACS
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.43.Mn Adsorption kinetics
62.20.Qp Friction, tribology, and hardness
68.03.Cd Surface tension and related phenomena
79.60.Dp Adsorbed layers and thin films
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