| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Monday Sessions |
| Session GR+SS+TF+EM-MoM |
| Session: | Epitaxial Graphene on SiC |
| Presenter: | C.R. Eddy, Jr., Naval Research Laboratory |
| Authors: | J.K. Hite, Naval Research Laboratory J.C. Culbertson, Naval Research Laboratory J.L. Tedesco, National Institute of Standards and Technology M.E. Twigg, Naval Research Laboratory A.L. Friedman, Naval Research Laboratory P.M. Campbell, Naval Research Laboratory R.L. Myers-Ward, Naval Research Laboratory C.R. Eddy, Jr., Naval Research Laboratory D.K. Gaskill, Naval Research Laboratory |
| Correspondent: | Click to Email |
Epitaxial graphene (EG) has lately garnered enormous interest, due to its high free-carrier mobility and compatibility with semiconductor processing. In fact, the first EG RF field effect transistor has been demonstrated.1 However, the growth mechanism of this material is not well understood. Current RF device work has been on the Si polar face of (0001) semi-insulating SiC substrates as EG on this face mainly consists of 1 monolayer of graphene. In contrast, the C-face consists of a dozen or more graphene layers and has a rougher morphology. Yet, there is significant interest in obtaining few layer, smooth EG on the C-face of SiC due to its better electrical properties as compared to the Si-face. Recently, it was shown that C-face EG grown in Ar ambient slows the growth rate, and under certain conditions results in islanding of the graphene on the C-face.2 These islands open the possibility of investigating the initial stages of graphene growth.
Electron channeling contrast imaging (ECCI) has previously been used to investigate threading dislocations in semiconductors such as GaN and SiC.3,4 In this work, ECCI is used for the first time to investigate graphene island morphology as a function of island size and growth conditions. Using this characterization tool, single threading screw dislocations (TSDs) have been found in the center of small EG islands (>20μm diameter). ECCI images confirm that these small graphene islands are forming in hexagonal recesses below the surface of the SiC substrate. For larger islands, the evidence of TSDs disappears suggesting that as the islands grow or coalesce to larger diameters either the TSD becomes buried or no longer contributes to growth. Once the islands become this large, the graphene begins to grow above the SiC surface, unlike the smaller islands. After removal of the EG by various methods, TSDs are still observed in the centers of the pits formed by the small island graphene growth. After some removal efforts, many pits retained small triangles of graphene around the TSD . These results are consistent with Raman and AFM maps of the islands that demonstrate that the centers of the islands are much deeper and the graphene thicker than the surrounding graphene. The evidence of TSDs in the centers of these C-face EG islands strongly suggests that these dislocations serve as nucleation sites for EG growth, where the TSD may provide an escape pathway for sublimated silicon atoms during the growth process.
1J.S. Moon et al., IEEE Electron Dev Lett 31, 260, 2010
2J.L. Tedesco et al., Appl Phys Lett, in press
3Y.N. Picard et al., Scripta Materiala 61, 773, 2009
4Y.N. Picard et al., Appl Phys Lett 90, 23401, 2007