Improvement of measurement sensitivity near contact in intensity-interferometry flying height testers

Microsystem Technologies, April 2014.

Korakoch Phetdee, Alongkorn Pimpin, Werayut Srituravanich.

 Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University, Pathumwan, Bangkok, 10330, Thailand.

 

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 DLC2of 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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