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Case Study : Diamond Like Carbon

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6.5.2. Diamond-Like Carbon
Diamond-like carbon (DLC), exhibits a number of properties similar to diamond. DLC is a family of amorphous carbon materials, existing in seven different forms that contain sp2 and sp3 hybridised carbon atoms. Sp2 refers to the graphite bonding structure, whilst sp3 refers to a diamond bonding structure. Graphite and diamond have very similar structures, but the bonding type differentiates them. By altering the ratio of sp2 to sp3 bonding and hydrogen content, different mechanical properties in DLC films are observed. Figure 6.26 shows a phase diagram illustrating different DLC coating structures and their bonding type. More sp2 bonding gives rise to films of lower hardness and abrasion resistance, but improved tribological properties. Films containing a higher proportion of sp3 bonding and less hydrogen have a tetrahedral structure similar tantamount to diamond, exhibiting high surface toughness but reduced ductility.56 The relative proportion of the two bonding types is highly dependent on the deposition method and processing parameters.57 Values of Young’s modulus have above 900GPa have been obtained.58 Nuclear magnetic resolution (NMR) and electron energy loss spectroscopy (EELS) are common techniques to characterise the hybridization of DLC films.59

Many potential applications exist due to the unique combination of properties DLC exhibits. Antireflective and abrasion resistant coatings for IR optics and smartphone touchscreens make use

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