▎ 摘　　要

To fabricate stable and high-quality graphene-silicon (Si) heterojunctions, it is of paramount importance to grow high-quality graphene on pristine Si surfaces directly and understand its growth mechanism. The performance of graphene-Si-based hybrid electronic/optoelectronic devices depends on the quality of such heterojunctions. Herein, we have carried out detailed density functional theory (DFT) and molecular dynamics (MD) simulation studies related to the metal-catalyst-free direct chemical vapor deposition (CVD) growth mechanism of graphene on the Si(100) surface, which is hardly reported to date. The DFT results suggest that the direct CVD growth of graphene on Si substrates is possible at high temperatures, and hydrogen passivation of Si surfaces does not affect the graphene growth. Moreover, X-ray photoelectron spectroscopy analyses of the direct thermal CVD-grown graphene on the Si(100) substrates reveal that the formation of silicon carbide (SiC) takes place even at 900 degrees C. This is in stark contrast to the results reported so far, where the graphene growth temperature exceeded 900 degrees C. It is concluded that high-temperature (>= 900 degrees C) direct CVD growth of graphene takes place on a self-limited thin SiC buffer layer instead of the actual Si substrate underneath, which is undesirable for fabrication of graphene-Si-based hybrid electronic/optoelectronic devices. Hence, high-temperature metal-catalyst-free direct growth of graphene on Si substrates using thermal CVD systems needs a revisit.