Investigation of superfast deposition of metal oxide and Diamond-Like Carbon thin films by nanosecond Ytterbium (Yb+) fiber laser

Abstract

Metal oxide (MOx, M: titanium, magnesium) and Diamond-Like Carbon (DLC) thin films were synthesized by Pulsed Laser Deposition (PLD) at room temperature and low vacuum of 2Pa for MOx and vacuum of 4×10−3Pa for DLC films. A fiber based Ytterbium (Yb+) laser operating in the nanosecond regime at a repetition rate of 20kHz was used as an ablation source. Dense and smooth thin films with a thickness from 120 to 360nm and an area of up to 10cm2 were deposited on glass and stainless steel substrates at high growth rates up to 2nm/s for a laser intensity of 10–12J/cm2. The thin films synthesis was compared for two fiber laser modes of operation, at a repetition rate of 20kHz and with an additional modulation at 1kHz. The morphology, chemical composition and structure of the obtained thin films were evaluated using optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Raman spectroscopy. The morphology of the MOx thin films and the deposition rate strongly depend on the fiber laser mode of operation. Very smooth surfaces were obtained for the metal oxide thin films deposited at lower deposition rates in the modulation mode at 1kHz. The effect of the substrate on the DLC film structure was studied. The films deposited on dielectric substrates were identified as typical tetrahedral (ta-C) DLC with high sp3 content. DLC films on metal substrates were found typical a-C amorphous carbon films with mixing sp2/sp3 bonds.