AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Monday Sessions
       Session AS+MI+VM-MoM

Paper AS+MI+VM-MoM4
Tribochemistry of Monodispersed ZDOL with Hydrogenated Carbon Overcoats

Monday, October 25, 1999, 9:20 am, Room 610

Session: Magnetic Recording: Chemical Integration and Tribology
Presenter: C.-Y. Chen, University of California, Berkeley
Authors: C.-Y. Chen, University of California, Berkeley
W. Fong, University of California, Berkeley
D.B. Bogy, University of California, Berkeley
Correspondent: Click to Email
Tribo-chemical studies of the lubricant molecular weight effect on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disks coated with ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated Al2O3-TiC sliders and thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. The studies showed that the lubricant interaction with the carbon overcoat varies as a function of lubricant molecular weight. The friction coefficient increases as the molecular weight increases. The higher friction is due to the higher viscosity. The friction and catalytic decomposition mechanisms of ZDOL are described. In general, the PFPE polymers are decomposed by chain scission involving the breakage of the backbone bonds to yield free-radical segments. Chain scission can occur by three mechanisms: (1) random degradation, (2) depolymerization, and (3) weak-link degradation. Our studies further support previous observations that catalytic reactions occurred at the endgroup functionals. The lower number of endgroup functionals for ZDOL with higher molecular weight reduces the possibility of the occurrence of catalytic reactions. Moreover, the ZDOL desorbed peak temperatures shifted to lower temperatures with increasing molecular weight in thermal desorption tests. The spreading diffusion coefficient of ZDOL decreases with increasing molecular weight. As the mobility of the lubricant chain decreases, the desorption energy needed to break the lubricants increases, resulting in higher desorption peak temperatures. In addition, the longer chain length of the higher molecular weight ZDOL causes higher degrees of crosslinking. The crosslinking restricts chain mobility and causes an increase in the desorption peak temperatures.