Diamond-like carbon thin films grown by large-area surface-wave mode microwave plasma CVD: Effects of stage distance to microwave window

Diamond-like carbon (DLC) thin films were grown on silicon and quartz substrates by using large-area surface-wave mode microwave plasma chemical vapor deposition at different distances from microwave quartz window. The chemical, optical, bonding and structural properties of the films were characterized by X-ray photoelectron spectroscopy, UV/VIS/NIR spectroscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. Nitrogen atomic concentration (%) of the films increased with decreasing the distance of substrate to microwave quartz window. Optical band gap of the films decreased from 2.7 to 2.4 eV when the substrate to microwave quartz window decreased from 12 to 3 cm. The FT-IR absorbance peaks of the DLC films in the region 2800–3000 cm− 1 became more and more prominent as the distance of substrate to the microwave quartz window increased from 3 to 12 cm, suggesting the formation of crystalline structure in the films. The increase of sp2 fraction with decreasing the distance of substrate to the microwave quartz window (i.e. increasing the electron density of the plasma) was conformed by Raman spectra of the films.