Frictional characteristics of diamond sliding on as-grown surfaces of large GEM quality single crystal synthetic diamond

Sliding friction measurements are reported on {{111}} and {{001}} surfaces of synthetic diamonds in the as-grown condition. The measurements were done in ambient air, and the lowest friction coefficient observed was 0.004 on {{111}} faces in 〈112〉 directions. The friction coefficient varies with sliding direction, as has been previously reported. The frictional energy loss is primarily associated with adhesion. Polished surfaces of natural diamonds were also measured for comparison. Ultra-fine polishing of a surface reduces the friction compared with a conventional polish. Synthetic diamonds with different dopants were investigated, but no correlation between friction and dopant was found.