Deposition of hydrogen-free diamond-like carbon film by plasma enhanced chemical vapor deposition

Hydrogen-free diamond-like carbon (DLC) films were deposited by the layer-by-layer technique using plasma enhanced chemical vapor deposition (PECVD), i.e., the alternative deposition of thin DLC layer and subsequent CF4 plasma exposure on its surface. The hydrogen-free DLC could be grown on the Si wafer by repeated deposition of the 5 nm DLC layer and subsequent 200 s CF4 plasma exposure on its surface. On the other hand, the conventional DLC deposited by PECVD contains 25 at. % hydrogen inside. The CF4 plasma exposure on the thin DLC layer appears to etch weak C–C bonds and break hydrogen bonds, resulting in a widening optical band gap and increasing conductivity activation energy.