We have studied van der Waals epitaxy of indium nitride (InN) on graphitic substrates using radio frequency plasma assisted molecular beam epitaxy (RF-MBE) and droplet elimination by radical ion beam (DERI) method. InN nanocrystals smaller than ~ 100 nm were densely grown on the single layer graphene supported on SiO2/Si while larger hexagonal shape nanocrystals larger than 500 nm were obtained on the thick graphite. Our result suggested that both defects on the graphitic substrate and flatness plays important role to limit the crystal size, such that these parameters act on the In droplet coverage at initial growth stage. With inserting aluminum nitride (AlN) buffer layer, the coalescent of these crystals can be improved and highly oriented wurtzite structure becomes dominant. These findings give the new insights for the improvement of the crystal growth of InN thin film.

We demonstrated that repetition of gallium deposition and nitrogen-rich supply is a superior approach to fabricate gallium nitride (GaN) thin films on graphene by electron-cyclotron-resonance plasma-excited molecular beam epitaxy. The gallium layer, which covered the surface at the initial growth stage, reduced nitrogen-plasma-induced damage to the graphene. It thereby might suppress the nucleation of misoriented crystals and enabled the growth of c-axis-oriented GaN films. This approach was more effective on graphene transferred onto a GaN template, which suggests the possibility of remote-homoepitaxy reflecting the electric potential of the GaN template unscreened by graphene.