“…Apart from the above, recent studies demonstrate the importance of surface chemistry and tribological environment on the nature of friction and wear [8,12,188,19]. For example, in a humid atmosphere, friction and wear of diamond and tetrahedral amorphous carbon films are significantly reduced due to surface passivation and chemical rehybridization of sp 3 to sp 2 bonding [8,12,18,20,21]. Further, CoF on diamond coatings reduces with decrease in surface roughness as reported by several groups [22,23,24].…”