Atomic Force Microscopy of Magnetic Rigid Disks and Sliders and Its Applications to Tribology

1991 ◽  
Vol 113 (3) ◽  
pp. 452-457 ◽  
Author(s):  
Bharat Bhushan ◽  
G. S. Blackman
Keyword(s):  
Disk Surface ◽  
Lateral Resolution ◽  
Measurement Tool ◽  
Lubricant Thickness ◽  
Strong Function ◽  
Force Microscopy ◽  
Real Area Of Contact ◽  
Atomic Force ◽  
Rigid Disks ◽  
Real Area

Surface topography measurements of magnetic rigid disks and a slider are made using an atomic force microscope (AFM) and a conventional noncontact optical profiler (NOP). The lateral resolution for the surface topographs spans the range of 1 μm down to 2 nm. Topography measurements are used to predict summit statistics and the real area of contact statistics. We find that contact statistics predictions are a strong function of the lateral resolution of the roughness measurement tool. As the magnetic slider comes into contact with the disk surface, the nanoasperities (detected by AFM) plastically deform instantly and subsequently the load is supported by the elastic deformation of microasperities (detected by NOP). AFM also allows the measurements of lubricant-thickness distributions on smooth surfaces. Examples for magnetic disks are presented.

Dynamic Modeling and Simulation of Rough Cylindrical Micro/Nanoparticle Manipulation with Atomic Force Microscopy

2014 ◽  
Vol 20 (6) ◽  
pp. 1692-1707 ◽  
Author(s):  
Moharam H. Korayem ◽  
Hedieh Badkoobeh Hezaveh ◽  
Moein Taheri
Keyword(s):  
Critical Force ◽  
Cylindrical Particle ◽  
Force Microscopy ◽  
Real Area Of Contact ◽  
Atomic Force ◽  
Rough Substrate ◽  
Simulation Results ◽  
Afm Probe ◽  
Cylindrical Particles ◽  
Simulation Condition

AbstractIn this paper, the process of pushing rough cylindrical micro/nanoparticles on a surface with an atomic force microscope (AFM) probe is investigated. For this purpose, the mechanics of contact involving adhesion are studied first. Then, a method is presented for estimating the real area of contact between a rough cylindrical particle (whose surface roughness is described by the Rumpf and Rabinovich models) and a smooth surface. A dynamic model is then obtained for the pushing of rough cylindrical particles on a surface with an AFM probe. Afterwards, the process is simulated for different particle sizes and various roughness dimensions. Finally, by reducing the length of the cylindrical particle, the simulation condition is brought closer to the manipulation condition of a smooth spherical particle on a rough substrate, and the simulation results of the two cases are compared. Based on the simulation results, the critical force and time of manipulation diminish for rough particles relative to smooth ones. Reduction in the aspect ratio at a constant cross-section radius and the radius of asperities (height of asperities based on the Rabinovich model) results in an increase in critical force and time of manipulation.

Tapping-mode AFM - Force Measurement Capabilities on Compliant Surfaces

2003 ◽  
Vol 790 ◽  
Author(s):  
Ijeoma M. Nnebe ◽  
James W. Schneider
Keyword(s):  
Force Measurement ◽  
Viscous Medium ◽  
Measurement Tool ◽  
Tapping Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Quantitative Extraction ◽  
Compliant Surfaces ◽  
Force Curves ◽  
Molecular Layers

ABSTRACTWe investigate the feasibility of tapping-mode atomic force microscopy (TM-AFM) as a force measurement tool for compliant surfaces. For quantitative extraction of the tip-sample interactions, numerical modeling of the cantilever dynamics is required using a defined form for the interaction, with the results compared to experiment. Through TM force measurements on silicon, we illustrate that a forced damped harmonic oscillator model sufficiently represents the motion of the cantilever. Particularly for liquid operation, distance-dependent dissipation must be included in the model for accurate quantification of the tip-sample interactions and for successful reproduction of experimental force curves. This dissipation is not due to damping from the bulk viscous medium, but is likely frictional in origin. This investigation shows that TM force measurement in liquid is feasible and could be particularly advantageous for the measurement of intermolecular interactions from soft and easily deformed molecular layers.

Effects of High Current Density at Nanoscale Point Contacts

2008 ◽  
Author(s):  
Hsinyi Lo ◽  
James A. Bain
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Thermal Contact ◽  
Initial Contact ◽  
Point Contacts ◽  
Conductive Atomic Force Microscopy ◽  
Strong Function ◽  
Force Microscopy ◽  
Au Film ◽  
Atomic Force

We examine the electrical/thermal contact between Pt-coated pyramidal Si probes and a 100 nm thick Au film using conductive atomic force microscopy (C-AFM). For all tips, the series resistance after initial contact was not a strong function of applied force over the observed range. Mechanical contact in this range of forces without an applied voltage between tip and Au film did not produce any observable tip deformation or wear as determined by SEM examination. Changes in tip morphology after applying voltage between the tips and Au film can be attributed to two different mechanisms. At relatively high applied voltages, evidence for tip melting was observed. Increases in tip/film contact resistance as a function of applied power allows an estimate of the thermal resistance experienced by heat generated at the tip and flowing to thermal ground. In addition to tip damage caused by melting, evidence was also seen of current induced welding of the Pt coating to the Au film in the absence of any significant heating at low applied voltages (10 mV). To explain the observation in the absence of sufficient temperature rise to induce melting, we characterize electromigration in the C-AFM and examine the maximum permissible current density of tips with different sizes as a function of stress.

Microstructures in Lubricant Thin Layers at the Magnetic Disk Surface, Observed Using Cryogenic Atomic Force Microscopy

2006 ◽  
Vol 59 (6) ◽  
pp. 394
Author(s):  
Teiji Kato ◽  
Takayuki Nakakawaji
Keyword(s):  
Atomic Force Microscopy ◽  
Disk Surface ◽  
Thin Layers ◽  
Solid Surfaces ◽  
Carbon Overcoat ◽  
Magnetic Disk ◽  
Force Microscopy ◽  
Atomic Force ◽  
Pfpe Lubricant ◽  
Atomically Flat

Cryogenic Atomic Force Microscopy (AFM) was used to observe perfluoropolyether (PFPE) lubricant molecules at atomically flat solid surfaces and at a magnetic disk surface to understand the lubricity of ultra-thin (1 nm) lubricant layers at the hard disk surface. Molecular imaging of PFPE lubricant molecules reveals the formation of reversed micelle structures at comparatively non-polar solid surfaces such as gold or the carbon overcoat of magnetic disks.

Role of Mechanical Properties and Surface Texture in the Real Area of Contact of Magnetic Rigid Disks

1989 ◽  
Vol 111 (3) ◽  
pp. 452-458 ◽  
Author(s):  
B. Bhushan ◽  
M. F. Doerner
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Surface Texture ◽  
Three Dimensional ◽  
Effective Elastic Modulus ◽  
The Real ◽  
Real Area Of Contact ◽  
Disk Structure ◽  
Rigid Disks ◽  
Real Area

The analysis of real area of contact for particulate and thin-film rigid disks is presented. The mechanical properties (hardness and modulus) of the disk structure are measured by a nanoindentation apparatus and the surface texture is measured by a three-dimensional noncontact optical profiler. For typical rigid disks selected for this study, we find that most contacts are elastic; the same observation was made by Bhushan (1984) for flexible media. In the case of elastic contacts, the real area of contact is governed by the effective elastic modulus of the disk structure and its surface summit distribution. Typical values for the fractional real area of contact, number of contacts per unit area, mean asperity diameter, and mean real pressure for a thin-film disk are calculated to be of the order of 5 × 10−5, 20/mm2, 1μm, and 200 MPa, respectively.

The effect of deformation on the lateral resolution of atomic force microscopy

1996 ◽  
Vol 182 (2) ◽  
pp. 106-113 ◽  
Author(s):  
J. YANG ◽  
J. MOU ◽  
J.-Y. YUAN ◽  
Z. SHAO
Keyword(s):  
Atomic Force Microscopy ◽  
Lateral Resolution ◽  
Force Microscopy ◽  
Atomic Force

A Method to Measure the Media Lubricant Loss After HAMR Recording

2016 ◽  
Author(s):  
Dongbo Li ◽  
Shaomin Xiong ◽  
David Braunstein ◽  
Xingcai Guo ◽  
Sripathi Canchi ◽  
...  
Keyword(s):  
Hard Disk Drives ◽  
Areal Density ◽  
Disk Surface ◽  
Thickness Variation ◽  
Laser Exposure ◽  
Lubricant Thickness ◽  
Thickness Change ◽  
Force Microscopy ◽  
Magnetic Switching ◽  
The Media

Heat assisted magnetic recording (HAMR) is anticipated to increase the areal density in hard disk drives to multiple Tb/in2. During HAMR recording, as a near filed laser light heats the media to the temperature above Curie point to assist magnetic switching, the lubricant that is typically applied to the disk surface will be under an intensive thermal stress, which will lead to the lubricant desorption and/or decomposition, and frequently accompanied with the underneath carbon overcoat (COC) graphitization and oxidation. Due to the optical properties change of the COC at such a high temperature, the traditional optical techniques are not appropriate to measure the lubricant thickness post HAMR recording. In this paper, we introduce a new method based on atomic force microscopy (AFM) in different imaging modes to detect the lubricant and also COC thickness change as a result of laser heating with a vertical resolution at the angstrom scale. Using AFM in a soft tapping mode, we can also characterize the lubricant thickness variation with time after laser exposure, which enables the measurement of the lubricant reflow kinetics on HAMR media.

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