Nanoindentation and Nanoscratching of Hard Coating Materials for Magnetic Disks
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at. Res. Soc. Symp. Proc. Vol. 356 ©1995 Materials Research Society
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Figure 1. Nanoindentation measurements of (a) hardness and (b) elastic modulus. 608 nm. The film was predominantly amorphous and contained a nitrogen concentration in the range 23-28 atomic %. An electron cyclotron resonance (ECR) microwave plasma system at the Oak Ridge National Laboratory was used produce the boron suboxide film (BOx). A high temperature effusion cell injected boron into an Ar/0 2 ECR plasma for deposition of the boron suboxide onto a silicon substrate maintained at temperatures in the 75-300*C range. The film was deposited at a microwave power of 1000 W, an oxygen concentration of 0.7%, a total gas pressure of 0.55 mTorr, and no rf bias. The 210 nm thick film contained 11 atomic % oxygen as determined by Rutherford Backscattering Spectrometry methods. Details of the system and processing conditions are given elsewhere 161. The mechanical behavior of the films was investigated using nanoindentation and nanoscratching techniques. Nanoindentation tests were conducted using a sharp Berkovich diamond to measure the hardness, H, and elastic modulus, E, of the films using the method developed by Oliver and Pharr [7]. Nanoscratching experiments were performed using a system described elsewhere [81 to qualitatively assess the relative resistance of the materials to scratching and to measure friction coefficients. The scratch experiments were performed with a Berkovich diamond oriented in a face-forward direction, i.e., with a face of the diamond, rather than an edge, in the direction of scratching. The diamond was not as sharp as those used in the nanoindentation testing, having been blunted by previous scratch experiments in hard ceramics. During each scratch test, the diamond was passed three times along the same 1000 gm long track at a constant velocity of 10 gm/sec while the normal displacements of the tip were monitored and recorded as a function of position along the track. In the first pass, hereafter referred to as the initial scan, an extremely light, constant load of 20 gN, which produced no damage or permanent deformation in any of the films, was applied to the diamond to map the slope and contour of the surface. The scratch was then produced in the second pass by linearly ramping the load from a minimum value of 20 LtN to a maximum of 100 mN as the specimen was translated underneath. After the load-ramped scratch was produced, a third pass, called the post-scratch scan, was used to trace the surface once again and establish the damage done to the film during the formation of the scratch. RESULTS AND DISCUSSION Nanoindentation Results of the nanoindentation tests are shown in Figs. la and b. S
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