The instability of angstrom-scale head-disk interface induced by electrostatic force

When the storage density is coming into several Tb/in², the head-disk spacing will drop into angstrom-scale regime [1]. At such small clearance, the electrostatic and intermolecular forces have become increasingly significant. It was reported that the electrostatic force produced by electronic potential difference between head and disk can be larger than the van der Waals force even if the slider and disk are both grounded[2],[3]. However, the electrostatic induced head disk interface instability and the relevant reliability were not well addressed in past. Therefore, this work investigates the instability of angstrom-scale head-disk interface induced by electrostatic force. First, the hysteresis effect of the touchdown-takeoff was investigated with/without eliminating the electronic potential difference. The electrical powers of thermal flying-height control (TFC) [4] head was supplied and then released to capture the hysteresis effect. It is found that a significant improvement of the hysteresis effect has been achieved when the electrostatic potential was eliminated. Second, a wear test over 60 hours when the head-disk clearance was set at an angstrom scale was performed. It is also found that the wear robustness has been greatly improved by eliminating the electrostatic potential. This study will help the design of the head-disk system for better reliability, especially for wear and flying stability.