Electrical conductivity improvement by iodine doping for diamond-like carbon thin-films deposited by microwave surface wave plasma CVD

We report the effects of iodine (I) doping on the optical and structural properties, and electrical conductivity of diamond-like carbon (DLC) thin-films grown on silicon, glass and quartz substrates by microwave surface wave plasma chemical vapor deposition at low temperature (< 100 °C). For film deposition, we used argon and methane as plasma source gases. The films were characterized by UV/VIS/NIR spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and current–voltage (I–V) characteristics. The optical band gap of the films decreased from 3.5 to 1.9 eV corresponding to non-doping to I-doping conditions. The XPS results confirm the successful doping of I in the films. The FTIR result shows the effect of I-doping on reduction of sp3-bonded carbon in the film. The I–V measurement shows I-doping induced electrical conductivity of the DLC film.