Iodine doping in amorphous carbon thin-films for optoelectronic devices

We report the effects of iodine doping on the optical and structural properties of amorphous carbon thin-films grown on silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (CVD) at low temperature (<100 °C). For film deposition, we used Ar and CH4 as plasma source gases. The films were characterized by UV/Vis/NIR spectroscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements. The optical band gap of the films decreased from 3 to 0.8 eV corresponding to non-doping to iodine doping conditions. The XPS results confirm the successful doping of iodine in the films. The Raman results show that iodine doping induced more graphitization in the films.