Self-Organized Growth of Nanowires on a Graphene Film

The self-organized growth of nanowires (NWs) on a graphene film is realized through the van der Waals epitaxy mechanism by metalorganic chemical vapor deposition. It is a fundamental phenomenon which is qualitatively different from the known growth mechanisms, such as self- and metal-catalyzed NW growth. We present a theoretical model that explains the self-organized nucleation of InGaAs NWs on graphene, starting from the formation of InAs NW segments. Then, newly formed InAs NWs act just like seeds to initiate the subsequent growth of InAs/In_xGa_1-xAs core-shell NWs with spontaneous phase segregation. The model shows that due to the introduction of the graphene film, the nucleation speed of InAs and InGaAs nanoislands in the horizontal direction far exceeds that of the vertical direction. It also elucidates why the radius of the InAs core is two times larger than the InGaAs shell thickness by considering the adatom collection ability of the InAs core and InGaAs shell, respectively, during the transformative process. Thus, the theoretical analysis of the self-organized NW growth on a graphene film is of vital importance for further optimizing the fabrication procedures of two-dimensional material-based NWs.