Ellipsometric measurement accuracy of ultrathin lubricant thickness on magnetic head slider
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The quantitative analysis of lubricant transferred from disk to slider is important in understanding the interaction in head-disk interface and designing a stable head-disk system. When applying ellipsometric technology to determine the lubricant thickness on slider, the measurement accuracy is of concern due to the location-to-location variations of slider optical constants. This paper carried out a systematic and quantitative study on how the variations of slider optical constants affect the measurement accuracy of lubricant thickness. In this study, the distribution of slider optical constant was obtained; a differential method was used to calculate the uncertainty in lubricant thickness and the calculated results were experimentally verified. The results show that for the state-of-art sliders, the uncertainty in lubricant thickness is about 20 % for below 2 nm thicknesses and less than 15 % for around 3 nm thicknesses when measured at 632.8 nm wavelength. The results of this study might be also useful for the other optical instruments used to determine the amount of the transferred lubricant.
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