▎ 摘　　要

Graphene films were grown onto two different thickness levels of SiO2/Si substrates, with the help of Ni film from highly ordered pyrolytic graphite through pulsed laser deposition. In this work, the influence of thickness of buffer layer of SiO2 on quality, growth, and crystallinity of graphene films in terms of substrate temperatures has been studied. All graphene samples were characterized by using Raman spectroscopy, Scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). The micro-Raman spectroscopic results clearly reveal that each SiO2/Si substrate does not behave in same manner during PLD growth process. From the Raman spectra, it was noticed that the quality, growth and crystallinity of graphene films was rapidly improved on commercially available SiO2 (100 nm)/Si substrates, while gradually improved on thermally grown SiO2 (400 nm)/Si substrates upon increasing growth temperature from 700 degrees C to 800 degrees C. Moreover, it was also observed from the Raman spectra that the number of graphene layers was found to be quite similar on both SiO2 layer at higher temperature of 800 degrees C. The microstructure of the as-synthesized graphene films also confirmed that the quality of graphene layers continuously improved over commercially available SiO2 substrates with the increment in substrate temperature. XPS results obviously verify that crystallinity and carbon-carbon bond strength increased while defects reduced on SiO2 (100 nm)/Si substrates with the increase growth temperature from 700 degrees C to 800 degrees C. Thus, the presented study provides a facile, rapid, and effective technique to control the quality, growth, and crystallite size of graphene films onto different thickness SiO2 layer on Si.