Characterization of boron-doped diamond-like carbon prepared by radio frequency sputtering

Instead of the sophisticated deposition processes and boron sources reported in literature, the study used the radio frequency magnetron sputtering method to prepare boron-doped diamond-like carbon (DLC) films with p-type conduction. The adopted sputtering targets were composed of boron pellets buried in a graphite disc. The undoped DLC films prepared exhibited n-type conduction, based on the Hall-effect measurement. For boron content ≥ 2.51 at.%, the films showed semiconductor behavior converted from n-type to p-type conduction after annealing at 450 °C. B-DLC films with a boron content of 5.91 at.% showed a maximum carrier concentration of 1.2 × 10¹⁹ cm⁻³, a mobility of 0.4 cm²/V s, and an electrical resistivity of 1.8 Ω cm. The results of XPS and Raman spectra indicated that the motion of boron atoms was thermally activated during post-annealing, helping promote the formation of C-B bonds in the films. Moreover, the doping of boron in DLC films decreased sp³ bonding and facilitated carbon atoms to form sp² bonding and graphitization.