Dirct Visualization of a Molecularly Thin Lubricant Film on a Magnetic Disk with a White Light Source-Based Ellipsometric Microscope

Abstract

In a magnetic disk drive, a molecularly thin film is currently used as a lubricant and controlling its kinetic behaviors is a key technology to design the head disk interface. Direct visualization of molecularly thin lubricant films is useful in investigating the kinetic properties. To meet this demand, we demonstrated that the real time visualization is possible by using the ellipsometric microscope with a laser light source. However, the SNR of the image was limited by noises due to the optical interference and the improvement of the SNR was needed for a thickness resolution of sub-nm. In this paper, we demonstrate that the noises due to the optical interference can be reduced by using a white light source with lower coherence. The achieved SNR for a PFPE film image is about 61.4 in the white light source-based ellipsometric microscope whereas the SNR was about 9.4 in the laser-based one. This result indicates that the white light source based ellipsometric microscope can provide the real time visualization with a sub-nm thickness resolution.