Comparative study between erbium and erbium oxide-doped diamondlike carbon films deposited by pulsed laser deposition technique

Abstract

Diamondlike carbon (DLC) films doped with the same fraction of erbium and erbium oxide were prepared by using 248 nm KrF pulsed laser deposition system. The effects of erbium and erbium oxide on the surface morphology, microstructures, and mechanical property of DLC were investigated. Transmission electron microscopy showed that both erbium and erbium oxide retained their initial oxidation states while embedded as metal or metal-oxide nanoclusters in an amorphous matrix. Atomic force microscopy showed that erbium-doped and erbium oxide-doped DLC films were smooth with rms of less than 0.2 nm and closely resembled pure DLC film. The Raman analysis showed broad peaks centering around 1550 cm−1 on both samples. The deconvoluted Raman spectra showed that the ID/IG value of DLC film increased from 0.38 to ∼0.55 in the presence of erbium and erbium oxide, and the estimated sp3 content for the DLC nanocomposite films was ∼56%–57%. X-ray photoelectron spectroscopy (XPS) confirmed that the C 1s peaks for DLC nanocomposite were slightly shifted from 285.2 eV (diamond) to 284.5 eV (graphite). The deconvolution of XPS spectra further confirmed the amount of sp3 content and revealed the presence of a higher fraction of SiC bonding in erbium oxide-doped DLC film. Microscratch tester results showed that the presence of erbium oxide improved the adhesion strength of DLC film from ∼1.72 to ∼2.19 N, which was more effective than erbium at the same concentration (∼1.89 N). The coefficients of friction of the erbium-doped DLC and erbium oxide-doped DLC films were similar to that of pure DLC. Erbium and erbium oxide showed similar influence on the surface roughness, coefficient of friction, and sp3 content on DLC films, but improved adhesion strength, which was correlated with the SiC bonding states, was observed on erbium oxide-doped DLC.