Preparation of Titanium-Doped Diamond-Like Carbon Films With Electrical Conductivity Using High Power Pulsed Magnetron Sputtering System With Bipolar Pulse Voltage Source for Substrate

Abstract

Titanium-doped diamond-like carbon (DLC) films with electrical conductivity are prepared by plasma-enhanced chemical vapor deposition using high-density pulsed Ar/C2H2 plasmas. Those plasmas are produced by high-power pulsed magnetron sputtering (HPPMS) system, whereas the titanium dope into the DLC films is carried out through titanium sputtering. A bipolar pulse voltage source is connected to the substrate and its holder. The HPPMS plasma temporally evolves during a pulse-on time of an HPPMS power source after the discharge is ignited. Then, the negative pulse voltage with a magnitude of 1.5 kV is applied for $10~\mu \text{s}$ before the application of the positive pulse voltage with the magnitude lower than 1 kV and the pulsewidth of 10– $15~\mu \text{s}$ . The fraction of the intensity related to sp2 carbon bond in X-ray photoelectron spectroscopy (XPS) C 1s spectrum is $\sim 80$ % or more for any film. On the other hand, the fraction of the intensity related to sp3 carbon bond is $\sim 20$ %, resulting in the preparation of the films with moderate hardness. The fraction of the intensity related to the titanium component in the overall XPS spectrum is lower than 8%, whereas that of titanium–carbon bond component in the overall XPS spectrum is lower than 1.5%. The conductivity of the prepared films markedly increases to 609 S/cm and its value depends on the amount of titanium–carbon bond. On the other hand, the film hardness ranges between 10 and 15 GPa and it does not strongly depend on the content of titanium.