What triggers epitaxial growth of GaN on graphene?
C. Barbier, L. Largeau, N. Gogneau, L. Travers, M. Morassi, A. Cattoni, C. David, M.
Tchernycheva, F. Glas and J.-C. Harmand, Université Paris-Saclay, CNRS, Centre de Nanosciences et de
Nanotechnologies (C2N), 10 Boulevard Thomas Gobert 91120, Palaiseau, France
C. Durand, J. Eymery, T. Zhou and G. Renaud, Université Grenoble Alpes, CEA, IRIG, 17 avenue
des Martyrs, 38000 Grenoble, France
H. Montigaud, Saint-Gobain, CNRS, Surface Verre & Interfaces, Aubervilliers, France.
Graphene can impose an epitaxial relationship to GaN without any other bulk crystalstructure underneath1. This offers a very attractive possibility to use graphene as a low-cost, compliant and easily transferable substrate for growing III-nitride heterostructures. Moreover, selective GaN growth can be achieved on graphene patterned on a carrier SiO2 layer2. Organized arrays of high-quality nanostructures can thus be obtained.
In the present study, we explore the mechanisms that govern this epitaxial growth by plasma-assisted molecular beam epitaxy. Graphene reactivity being weak, GaN nucleation is not detected before a long incubation time, typically 1 hour in our experimental conditions at 815°C. We seek for surface changes that may occur during this incubation period and that could trigger GaN nucleation. Our studies indicate that the exposure to N plasma can produce small pits in the graphene layer (Figure 1a). In addition, we find that N atoms become incorporated into pyridinic sites (Figure 1b), which could be the anchor points of GaN nuclei. Next, we follow the nucleation stage by in situ X-ray diffraction. We monitor the GaN in plane lattice parameter. The first nuclei are tensely strained on the graphene and the GaN nanocrystals relax as they grow 3 . All these observations tend to show that, in our case, the cohesion of the GaN/graphene interface is not only due to van der Waals interactions. It is likely that chemical bonds are
involved in the epitaxial relationship.
This work is financially supported by the French RENATECH network and the French National
Research Agency (GaNEX).
1 V. Kumaresan, L. Largeau, A. Madouri, F. Glas, H. Zhang, F. Oehler, A. Cavanna, A. Babichev, L. Travers, N.
Gogneau, M. Tchernycheva and J.-C. Harmand, Nano Lett. 2016, 16 (8), 4895–4902.
2 M. Morassi, N. Guan, V. Dubrovskii, Y. Berdnikov, C. Barbier, L. Mancini, L. Largeau, A. V. Babichev, V. Kumaresan,
F. H. Julien, L. Travers, N. Gogneau, J.-C. Harmand and M. Tchernycheva, Cryst. Growth Des. 2020, 20, 2, 552–559
3 C. Barbier, T. Zhou, G. Renaud, O. Geaymond, P. Le Fèvre, F. Glas, A .Madouri, A. Cavanna, L. Travers, M. Morassi,N. Gogneau, M. Tchernycheva, J.-C. Harmand and L. Largeau, Cryst. Growth Des. 2020, 20, 6, 4013–4019
