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Observations of Depth-Sensing Reciprocating Scratch Tests of DLC and Nitrogenated-DLC Overcoats on Magnetic Disks

Published online by Cambridge University Press:  10 February 2011

T.W. Scharf ,
R.D. Ott ,
D. Yang  and
J.A. Barnard
T.W. Scharf
Affiliation:
Department of Metallurgical and Materials Engineering and The Center for Materials for Information Technology, The University of Alabama, Tuscaloosa AL 35487-0202.
R.D. Ott
Affiliation:
Department of Metallurgical and Materials Engineering and The Center for Materials for Information Technology, The University of Alabama, Tuscaloosa AL 35487-0202.
D. Yang
Affiliation:
Department of Metallurgical and Materials Engineering and The Center for Materials for Information Technology, The University of Alabama, Tuscaloosa AL 35487-0202.
J.A. Barnard
Affiliation:
Department of Metallurgical and Materials Engineering and The Center for Materials for Information Technology, The University of Alabama, Tuscaloosa AL 35487-0202.
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Abstract

In this investigation, the wear durability of existing and candidate protective overcoats and substrates was examined. Specifically, 5 nm thick diamond-like carbon (DLC) and nitrogenated diamond-like carbon (N-DLC) overcoats were deposited by sputtering onto glass, glass-ceramic, and NiP/AlMg substrates. The magnetic medium was a 15 nm thick layer of CoCrPt deposited on a 50 nm thick underlayer of CrV. The wear resistance of the hard disks was determined by a recently developed depth sensing reciprocating scratch test using the Nano Indenter© II. During the scratch tests, a constant normal load of 30 jtN was maintained at an indenter velocity of 2μm/sec. It was found the N-DLC/CoCrPt/CrV/glass disk exhibited the most wear resistance and least amount of plastic deformation after the last wear event. Conversely, the NDLC/CoCrPt/CrV/NiP/AiMg disk displayed the least wear resistance even though the magnitude of the elastic recovery was the greatest. This amount of recovery was influenced by the high elastic modulus of the NiP/AIMg substrate. Consequently, the scratch test failed to isolate the intrinsic properties of the overcoat, however it provided a very powerful means of quantitatively assessing the overall response of the whole magnetic disk. This is more relevant since it simulates the response the disks see in performance. In addition, a discrete amount of nitrogen up to 14 atomic % incorporated into the amorphous network resulted in an increase in overcoat durability compared to the DLC overcoat. This was attributed to an increase in the XPS determined number of N-sp3 C bonded sites in a predominantly N-sp2 C bonded matrix. However, with increasing nitrogen concentrations ≥18%, the film structure was weakened due to the micro-Raman spectroscopy determined formation of terminated sites in the amorphous carbon network since nitrogen failed to connect the sp2 domains within the network.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 517: Symposium F – Wide Bandgap Semiconductors for High Power, High Frequency , January 1998 , 389
Copyright
Copyright © Materials Research Society 1998

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