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

In this study, we prepared Q-carbon by adjusting the sp(3) 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 (lambda = 248 nm). The sp(3) 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/cm(2). The prepared films were characterized using scanning electron microscopy, Raman spectroscopy, and magnetization measurements. Consequently, for the combination of 20% sp(3) content and laser density of 1.0 J/cm(2), as well as 42% sp(3) and 0.5 J/cm(2), 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% sp(3) content. The results indicate that Q carbon can be obtained by using a proper combination of sp(3) content in DLC films and an appropriate PLA energy density. This study provides important guidance for establishing a preparation method for Q carbon. (C) 2020 Elsevier Ltd. All rights reserved.