The Instability of Angstrom-Scale Head-Disk Interface Induced by Electrostatic Force

When the storage density is several Tb/in², the head-disk spacing will drop into an angstrom-scale regime. At such small clearance, the electrostatic force (EF) becomes increasingly significant. However, the electrostatic-induced head-disk interface (HDI) instability and the relevant reliability were not well addressed in the past. Therefore, this paper investigates the instability of angstrom-scale HDI induced by the EF. First, the hysteresis effect of the touchdown-takeoff was investigated with/without eliminating the surface potential difference. The electrical powers of thermal flying-height control head were 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 for over 60 h was performed when the head-disk clearance was set at an angstrom scale. 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.