Abstract
In the hard disk drive, the spacing between the read/write head and the magnetic disk or flying height has been greatly reduced to a few nanometers to achieve ultrahigh-density magnetic storage. At flying heights below 10 nm, intensity-interferometry flying height tester, the major technique for flying height measurement suffers from low measurement sensitivity. This paper reports a simple and inexpensive method to improve the sensitivity of intensity-interferometry method for measuring flying heights down to contact by using a glass disk coated with multiple layers of silicon and diamond-like carbon (DLC) films. The optimum film thicknesses were selected in order to improve the measurement sensitivity by theoretically analyzing the light interference at the head-disk interface. The improved sensitivity was confirmed in experiments performed in a flying height tester. It was found that the measurement sensitivity at very low flying heights (0–20 nm) was improved by 85 % using a glass disk coated with four layers: Si1 of 1 nm, DLC1 of 55 nm, Si2 of 3 nm and DLC2 of 25 nm. The proposed method not only significantly improves the sensitivity, but it also considerably increases the durability of glass disks promising the application of the intensity-interferometry flying height tester for measuring flying heights down to contact.
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Acknowledgments
The authors would like to thank the following people at Western Digital (Thailand) for support in sample preparation and experiment: Theerasak Sa-nguanmanasak, Payung Muangngam, Theerawat Kaewmanee, Sonthirat Klankrong, Phuwanai Bunnak and Latchanan Rakkhatham. This work was supported by Industry/University Cooperative Research Center (I/UCRC) in HDD Advanced Manufacturing, Institute of Field Robotics, King Mongkut’s University of Technology Thonburi and National Electronics and Computer Technology, National Science and Technology Development Agency under the grant no. HDD 04-01-52. This work was also supported by Special Task Force for Activating Research (STAR) of Chulalongkorn University, Thailand through Micro-Nano Fabrication Technology Research Group (GSTAR 56-005-21-002).
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Phetdee, K., Pimpin, A. & Srituravanich, W. Improvement of measurement sensitivity near contact in intensity-interferometry flying height testers. Microsyst Technol 21, 49–53 (2015). https://doi.org/10.1007/s00542-014-2146-3
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DOI: https://doi.org/10.1007/s00542-014-2146-3