Structure and properties of diamond-like carbon thin films synthesized by biased target ion beam deposition

Abstract

Biased target ion beam deposition (BTIBD) was firstly used to synthesize hydrogen free diamond-like carbon (DLC) thin films. The structure and properties of the synthesized films were characterized by atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation, and ball-on-disk testing. The effect of target bias voltage, ranging from −200 to −1000V, on the structure and properties of the films was investigated. The results show that the sp3 bonding content increases from 20% to 60%, the root-mean squared (RMS) roughness decreases from 0.2nm to 0.05nm, the coefficient of friction (COF) decreases from 0.3 to 0.06, the hardness increases from 4.5GPa to 15GPa, and the Young's modulus increases from 65GPa to 170GPa with increasing the absolute value of target bias voltage from 200V to 800V. However, when the target bias voltage further increased to −1000V, the sp3 bonding content decreases to 44%, RMS roughness increases to 0.09nm, COF raises to 0.11, hardness decreases to 12.9GPa and Young's modulus is lowered to 150GPa. It has been found that the higher the fraction of sp3 bonds, the lower the surface roughness and friction coefficient, and the higher the hardness and Young's modulus.