Tuning the optical, electrical, and structural properties of Cu-DLC thin films via simultaneous DC-RF unbalanced...

This study evaluates the deposition of diamond-like carbon (DLC) films with copper impurities on a glass substrate using simultaneous direct current (DC) and radio frequency (RF) magnetron sputtering. The structural, optical, electrical, and mechanical properties, as well as the surface topography of the films, were investigated under various DC power levels using Raman spectroscopy, ellipsometry, UV-VIS, I-V measurements, nanoindentation, AFM, and FESEM. Results indicate that increasing the DC power to the graphite target from 60 to 120 W, while maintaining a constant 10 W of RF power to the copper target, enhances the optical absorption coefficient of the films and increases the optical bandgap from 0.95 eV to 1.55 eV. Concurrently, the refractive index decreases from 1.84 to 1.64. Raman spectra reveal that the G peak position and the I_D/I_G ratio decrease, suggesting an increase in sp³ bonds relative to sp² bonds in the film structure. The surface topography shows increased deposition power raises the surface roughness of the films. Optical emission spectroscopy (OES) during deposition indicates that higher DC power reduces the relative intensity of Cu active species, leading to less Cu embedded in the film structure. Additionally, the emission spectrum shows an increase in hydrogen-containing species, suggesting a rise in sp³ C-H bonds compared to sp³ C-C bonds in the film structure.