Investigation of slider surfaces after wear using photoemission electron microscopy

Abstract

The tribo-chemical interactions between the slider and the hard disk surface strongly influence the performance properties of a disk drive. To study these interactions, uncoated and carbon coated sliders were subjected to various wear tests using different disks. After the wear, the test slider surfaces were studied by photoemission electron microscopy (PEEM) using tunable x rays produced by a synchrotron. Using PEEM, one can identify the elemental and chemical state of the surfaces with a high spatial resolution. It was found that wear reduces the thickness of the carbon coating in some local areas of the slider surface. In particular, the coating was removed on elevated areas and in scratches. Scratches were found on the rails of the carbon coated and uncoated sliders after wear that showed the accumulation of a degraded (oxidized) lubricant which was transferred to the slider from the disk. It was also possible to analyze the chemical composition of the debris found on the slider surface. In the present case, the debris had the same chemical composition as the carbon coating of the slider.

Accounting for Nanometer-Thick Adventitious Carbon Contamination in X-ray Absorption Spectra of Carbon-Based Materials

“…For carbon K-edge NEXAFS spectroscopy, in particular, the resolvable energy difference between the resonant X-ray excitations of a core-level (1s) electron to unoccupied molecular orbitals (either π* or σ*) allows the identification of the bonding configuration and hybridization state of carbon atoms in the near-surface region for many materials, including diamond 6,13,21,22,24,25,[33][34][35][36][37][38] , diamond-like carbon [39][40][41][42][43][44][45][46] , graphene 26,47,48 , and polymers [27][28][29][30][31][32] , as well as the determination of the surface molecular orientation of nanomaterials 18,19,49,50 and adsorbates [14][15][16] .…”

Some Applications of Cathodic Arc Coatings

“…Hardness becomes less of an issue since such extremely thin films cannot withstand great mechanical forces: such films serve mainly as a corrosion protection coating. Corrosion can occur as part of the tribological use of the coating, and therefore specific investigations have been made characterizing the abrasion and corrosion behavior in controlled tribological environments [74,75,76].…”

Chemical Modification in Wear Tracks of Chemical Vapor-Deposited Diamond Surfaces Studied with X-ray Absorption Spectroscopy

“…In another study [3], worn amorphous carbon surfaces showed that certain tribochemical reactions took place when lubricants were present. The appearance of extra structures in the NEXAFS spectra were interpreted as the formation of ketone bonds (C=O) and carboxylic bonds (O=C-OH), mainly related to the chemical degradation of the lubricants during the wear process.…”

“…NEXAFS obtained in the total electron yield (TEY) mode probes only a few nanometers deep below the surface [3] and is therefore an excellent tool to study chemical modification close to the surface as is expected to occur in the type of wear processes presented in this work.…”

“…For reference, we have also plotted spectra from (i) graphite (bottom curve) and (ii) a CH x coated slider [3] after a sliding test with a lubricant (''a-C wear track'' in Fig. 2b).…”