Formation of Q-carbon by adjusting sp3 content in diamond-like carbon films and laser energy density of pulsed laser annealing

Abstract In this study, we prepared Q-carbon by adjusting the sp3 content in diamond-like carbon (DLC) films and the laser energy density of pulsed laser annealing (PLA). The amorphous DLC films were fabricated on sapphire Al2O3(0001) substrates using a pulsed laser deposition technique with a KrF excimer laser (λ = 248 nm). The sp3 content in the films varied between 20% and 42% by changing the laser energy density. Subsequently, PLA was performed on the DLC films by using the KrF excimer laser with energy densities between 0.5 and 1.2 J/cm2. The prepared films were characterized using scanning electron microscopy, Raman spectroscopy, and magnetization measurements. Consequently, for the combination of 20% sp3 content and laser density of 1.0 J/cm2, as well as 42% sp3 and 0.5 J/cm2, the films showed the characteristic features of Q-carbon: filamentary nanostructures, the presence of a T band in the Raman spectrum, room-temperature ferromagnetic behavior, and ∼80% sp3 content. The results indicate that Q-carbon can be obtained by using a proper combination of sp3 content in DLC films and an appropriate PLA energy density. This study provides important guidance for establishing a preparation method for Q-carbon.