As areal density increases and fly height decreases in hard disc drives, it becomes more difficult to achieve a reliable flying interface between the recording head and the disc. Manufacturing variations, environmental conditions and other factors can cause mechanical spacing losses. One method to compensate for these losses is to control slider clearance using electrostatic force. An attractive force between the slider and the disc can be generated by grounding the disc and applying voltage to the entire slider body or a dedicated electrode. If the applied voltage exceeds the breakdown voltage of the head-disc interface (HDI), however, the resulting current flow will cause damage to the head and disc and ultimately cause the head to crash. A series of experiments were performed on flying heads and a MEMS small-gap tester to determine the nature of the current flow and the effects of head coatings and disc lubricant on breakdown voltage. The results support field emission as the current flow mechanism. In addition, a thick diamond-like carbon (DLC) coating on the slider or electrode increases breakdown voltage and may prove to be an enabler for electrostatic fly control. In comparison, lube appears to have only a secondary effect on electrical breakdown.

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