Effects of positively and negatively pulsed voltages on the microstructure of DLC films prepared by bipolar-type plasma based ion implantation

Diamond like carbon (DLC) films were prepared by the bipolar-type plasma based ion implantation, and the microstructure was examined as a function of positively and negatively pulsed voltages ( V p and V n) by transmission electron microscopy (TEM) and Raman spectroscopy. Densities of the films were obtained from Rutherford backscattering spectrometry, elastic recoil detection analysis and surface profilemeter measurements. It was found that the density of the film was approximately 2.0 g/cm 3 and slightly decreased with increasing V p and V n. TEM observation revealed that DLC films were amorphous structure and small size disordered graphite structure appeared as V p increased. With increasing V n, however, turbostratic structure was clearly developed. Raman spectra were fitted by 4 peaks ( D 1: 1190 cm − 1 , D 2: 1380 cm − 1 , G 1: around 1550 cm − 1 and G 2: 1590 cm − 1 ). The G 1 peak shifted to higher wave numbers and the intensity of G 2 peak was increased with increasing V p. In addition, the intensity ratio of D ( D 1 + D 2) to G ( G 1 + G 2) peaks was also increased. These results suggested that graphite structure was formed as V p increased. With increasing V n, on the other hand, the G 1 peak did not shift so much and the intensity of G 2 peak was decreased. This corresponds to the development of the turbostratic form (t-DLC). The influence of electron and ion bombardment induced by V p and V n on the microstructure was discussed.