Epitaxial Graphene Grown on 4H-SiC with Excess Electrons Injected by Electron Beam Irradiation

Abstract

It is experimentally demonstrated that epitaxial graphene (EG) films with high crystallinity can be grown on a semi-insulating 4H-SiC(0001) substrate by irradiating electron beam (e-beam) onto the surface. The growth temperature is estimated to be ~850 ℃ significantly lower than the conventional thermal annealing in vacuum or Ar atmosphere. The excess electrons injected in the shallow region near the 4H-SiC surface are found to reduce the binding energy between Si and C atoms from density functional theory calculation. This reduced binding energy can initiate the sublimation of Si atoms, the trigger of EG growth, at such low temperature mentioned previously. Raman spectrum analysis and atomic force microscopy images show that monolayer graphene forms with e-beam being irradiated at 8 kV acceleration voltage and 7 mA current for 5 min, corresponding to electron fluency ~3.281020 e/cm2. The charge carrier (electron) density and its Hall mobility of EG grown at 7 mA current for 7 min (electron fluency ~4.591020 e/cm2) were found to be ~3.081012 cm-2 and ~994 cm2/Vs, respectively. The electrical properties of EG grown on a semi-insulating 4H-SiC substrate appear improved noticeably compared to EG grown also by e-beam irradiation on an amorphous SiC film and n-type doped 6H-SiC substrate [1,2].

[1] Go, H., Kwak, J., Jeon, Y., Kim, S. D., Cheol Lee, B., Suk Kang, H., ... & Park, K. Applied Physics Letters, 101(9), 092105 (2012). [2] Jin, H., Lee, J. Y., Kim, J., Jung, S., Mo, K., & Park, K. Current Applied Physics, 18(3), pp. 335-339 (2018).