Abstract
Fabrication of wear resistant and low friction carbon films on the engineered substrates is considered as a challenging task for expanding the applications of diamond-like carbon (DLC) films. In this paper, pulsed laser deposition (PLD) technique is used to deposit DLC films on two different types of technologically important class of substrates such as silicon and AISI 304 stainless steel. Laser power density is one of the important parameter used to tailor the fraction of sp2 bonded amorphous carbon (a-C) and tetrahedral amorphous carbon (ta-C) made by sp3 domain in the DLC film. The I(D)/I(G) ratio decreases with the increasing laser power density which is associated with decrease in fraction of a-C/ta-C ratio. The fraction of these chemical components is quantitatively analyzed by EELS which is well supported to the data obtained from the Raman spectroscopy. Tribological properties of the DLC are associated with chemical structure of the film. However, the super low value of friction coefficient 0.003 is obtained when the film is predominantly constituted by a-C and sp2 fraction which is embedded within the clusters of ta-C. Such a particular film with super low friction coefficient is measured while it was deposited on steel at low laser power density of 2 GW/cm2. The super low friction mechanism is explained by low sliding resistance of a-C/sp2 and ta-C clusters. Combination of excellent physical and mechanical properties of wear resistance and super low friction coefficient of DLC films is desirable for engineering applications. Moreover, the high friction coefficient of DLC films deposited at 9GW/cm2 is related to widening of the intergrain distance caused by transformation from sp2 to sp3 hybridized structure.
Highlights
Carbon and its allotropes in the form of thin films have enormous applications, including exceptional tribological performance in various extreme operating conditions.[1,2,3,4] The most crucial factors that rules the properties of the carbon films is the distribution and quantification of the different carbon hybridization states viz., linear sp[1], planer sp[2] and three dimensional tetrahedral covalent sp[3] bonds
Laser power density is one of the important parameter used to tailor the fraction of sp[2] bonded amorphous carbon (a-C) and tetrahedral amorphous carbon made by sp[3] domain in the diamond-like carbon (DLC) film
The I(D)/I(G) ratio decreases with the increasing laser power density which is associated with decrease in fraction of a-C/tetrahedral amorphous carbon (ta-C) ratio
Summary
Carbon and its allotropes in the form of thin films have enormous applications, including exceptional tribological performance in various extreme operating conditions.[1,2,3,4] The most crucial factors that rules the properties of the carbon films is the distribution and quantification of the different carbon hybridization states viz., linear sp[1], planer sp[2] and three dimensional tetrahedral covalent sp[3] bonds. In addition to that it is chemically inert and biocompatible.[12,13,14]
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