Laser generation of elliptical nanometre and sub-nanometre bump arrays on NiP/Al data storage disks and their effect on stiction performance

Elliptical nano-bumps on nickel-phosphorus coated aluminium (NiP/Al) hard disks were fabricated by a laser texturing system (maximum power 8 W, maximum frequency 300 kHz). By carefully selecting the level of laser power attenuation and defocus offset distance, bump height can be controlled below 6 nm and down to the sub-nanometre scale. This type of laser-induced texture (elliptical shape) on a disk surface is expected to provide better control of the stiction force along with the smallest separation distance between the head slider and the disk. Quantitative modelling based on the classical Hertzian theory for elliptic contacts has been carried out with the purpose of predicting the stiction behaviour of the presented elliptical shaped sub-10 nm bumps. It has been found that an elliptical shape not only reduces the overall stiction performance of the laser texturing zone (LZT) compared to the conventional circular shape but also extends the occurrence of the 'stiction wall' towards the sub-10 nm regime for ultra-low-glide applications.