Observation and Analyses of Nano-Spreading Molecularly Thin Functional Tribo-Film

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A novel method for measuring lubricant film thickness distribution has been developed based on the Michelson interferometry using the Linnik microscopy. The purpose of this measurement is to clarify the spreading phenomenon of giant molecular lubricant coated over magnetic disks. Optical interferencial fringes were formed across the boundary between with-lubricant and without-lubricant regions. A cross section of the lubricant was detected as a ridgeline of the fringe through image processing. First, a fringe following technique which enabled us to fix the image on a CCD frame and a noise cancellation technique by subtracting the image noise from the measured image, resulted in an increased accuracy through suppressing various kinds of image noise. Next, formulation for a calibration curve was derived, and a powerful method of utilizing the back reflection was proposed wherein the inner back surface reflection of a glass disk having a lubricant on its back surface was detected from the front side. This method has an advantage of no decreasing resolution different from the case of using the front reflection. A high resolution of 2 nm was achieved for the back reflection, while that of 8 nm for the front reflection. Finally, the phase shift method was applied to the present method by using the 7 buckets technique for unwrapping and the phase shift-supported method was confirmed to exhibit useful applicability to a three-dimensional measurement of the spreading phenomenon arising over the magnetic disks.