Real-Time Visualization of a Shearing Nanometer-Thick Lubricant Film by Two-Stage Imaging Ellipsometric Microscopy

A two-stage imaging ellipsometric microscopy with high lateral resolution and a wide field of view has been developed that will enable real-time visualization of the dynamic behavior of the nanometer-thick lubricant film used in head-disk interfaces incorporating contact or intermittent contact recording technology when it is sheared by the head. The first stage forms an object image at a low magnification ratio, which reduces the angle between the object image and the image sensor. This enables the first object image to be positioned perpendicular to the optical axis of the second stage. The second stage forms a final image on the image sensor at a high magnification ratio. As a result, both submicrometer lateral resolution and a wide field of view (115 μm × 85 μm) were achieved. A lubricant film sheared by an optical fiber probe with a micro ball at its end was visualized, and a bump due to meniscus formation during the intermittent contact was observed. This ellipsometric microscopy can thus visualize nanometer-thick sheared lubricant film in real time, which will be useful in the development of hard disk drives with higher recording density.