Molecular Dynamic Simulation Of The Tribological Properties Of Ultra-thin Films Of Hard Disk Drives

Hard disk drives (HDDs) using magnetic storage technology are widely used,because of its excellent properties of storage security, storage capacity and economy.Currently, Winchester technology is widespreadly adopted in HDDs with a sealedstructure consisting of a disk for storing data and a head for reading and writtingdata. To increase the storage density, the head flying height has been reduced to5nm, and the head and the disk are in quasi-contact state. When an accidental shockor vibration happens to a working hard disk, the protective films of the head anddisk easily contact and rub with each other directly, which would cause a wear ofthe film and make its protection fail, and even destroy the hard disk and make thedata loss. Therefore, the study of the tribological properties of the protective film ofthe hard disk could help to increase the work reliability and extend its service life.So far, therer are a lot of researches on the mechanical and tribological properties ofDLC films under the conventional magnetic storage technology, but no enoughinvestigation about the effect of heat-assisted magnetic recording technology on theprotective properties of DLC films has been done; With the decreasing of DLC filmthickness, the defects of large internal stress and poor adhesion are more obvious,experimental study shows that the incorporation of impurities can improve the DLCfilm defects, but the studies of the tribological properties of doped DLC are notsufficient; Due to excellent features, SiNx films is extremely suitable as a newgeneration protective film of hard disk. However, the preparation technology limitsits practical application, and the awareness of its tribological properties in ultrathinstate is lack. In this paper, the following studies were conducted using moleculardynamics simulations in view of the present research situation:Firstly, amorphous DLC film was model, and the microstructure changes ofthe DLC film was studied under the impact of the laser heating of heat-assistedmagnetic recording technology using molecular dynamic simulation. Then, afriction model of a sphere rubbing with a flat was established, and the tribologicalproperties of DLC films were studied at different temperature. Finally, theinfluence of different loads and the substrate on the triboligical properties of DLCfilms were investigated. And a qualitative approach was come up to describe thefriction strength.Si-DLC models with different Si content and different density were eatablished,respectively. Firstly, the microstructure of Si-DLC film was annlyzed. And themechanical properties of the Si-DLC films were studied by nanoindentation using molecular dynamic simulation. Then, the tribological properties of the Si-DLCfilms with different Si content and different density were investigated, respectively.Finally, the surface morphologies of Si-DLC films after friction were analyzed tostudy the wear properties of Si-DLC.According to the form of Tersoff potential, a modified potential function wasused to describe the interaction among C, Si and N atoms during the simulation.Firstly, the crystalline and amorphous silicon nitride films were modeled. Then, theimpact of different loads, friction direction and velocity, the film thickness on thetribological properties of crystalline silicon nitride films were studied. Finally, theinfluences of the normal load, the ratio of Si and N atomsand indenter radius on thetribological properties of amorphous silicon nitride films were investigated.