STM 10

Epitaxial graphene growth on porous 4H-SiC(0001)

Nanoporous materials represent a versatile solution for many applications ranging from sensing, energy applications, catalysis, drug delivery, and many others. The growth of epitaxial graphene in a 3D arrangement on the contour of a porous backbone allows the realization of a high quality graphene three-dimensional structure. Indeed, the synergy between the outstanding properties of graphene with a three-dimensional porous structure, circumventing the limits of the 2D nature of graphene, constitutes therefore a breakthrough for many fields.

The porous SiC material is obtained via a sequence of metal-assisted photochemical and photoelectrochemical etching in hydrofluoric acid based electrolytes. The fabrication process has already been optimized and allows to control the local definition of the pores as well as the degree of porosity with depth. Moreover, the porosification technique allows obtaining stacked layers of different porosity, increasing the versatility of this material.


Figure 1: SEM images of the porous 4H-SiC substrate. (a) Sample surface and (b) cross section.

The graphene growth is performed by thermal decomposition of the SiC, annealing the samples in an UHV environment with a base pressure of 5 × 10−11 mbar. The growth has been performed on both Si-face and C-face substrates in a temperature range 1200-1400°C. The graphene growth inside the pores is uniform as confirmed by Transmission Electron Microscopy (TEM) analysis. Raman spectroscopy confirms the high quality of the graphene with a 2D/G intensity ratio > 1 and an average graphene crystal size of ≈ 100 nm. Furthermore, it demonstrates a uniform coverage of graphene across the whole sample area accessible to the Raman probe.


Figure 2: (a) Raman spectrum of graphene on the top surface of the sample. (b) TEM image of the pore structure, inset: electron tomography reconstruction of the pore structure; light blue: pores volume, and yellow: SiC substrate. (c) High resolution TEM image of part of a pore with stacked graphene layers.

Publications:

  1. Stefano Veronesi, Georg Pfusterschmied, Filippo Fabbri, Markus Leitgeb, Omer Arif, Daniel Esteban Arenas, Sara Bals, Ulrich Schmid, Stefan Heun: 3D arrangement of epitaxial graphene conformally grown on porousified crystalline SiC, arXiv:2112.11319 [cond-mat.mtrl-sci].
  2. S. Veronesi, G. Pfusterschmied, F. Fabbri, M. Leitgeb, O. Arif, D. A. Esteban, S. Bals, U. Schmidt, S. Heun: 3D arrangement of epitaxial graphene conformally grown on porousified crystalline SiC, Carbon 189 (2022) 210 – 218.
  3. CNR Press Release
  4. Press Coverage in the Italian Newspaper La Repubblica
  5. Interview of Italian TV RAI 3 TGR Leonardo with Stefano Veronesi (08 March 2022 at 14:50). [Video]
  6. Press Coverage in the Italian Newspaper FORTUNE
  7. Stefano Veronesi, Ylea Vlamidis, Letizia Ferbel, Carmela Marinelli, Chiara Sanmartin, Isabella Taglieri, Georg Pfusterschmied, Markus Leitgeb, Ulrich Schmid, Fabio Mencarelli, Stefan Heun: Three-dimensional graphene on a nano-porous 4H-SiC backbone: a novel material for food sensing applications, arXiv:2309.13431 [physics.app-ph].

Presented at:

  1. Stefano Veronesi: Immagazzinamento di idrogeno in materiali 2D e 3D basati su grafene, RE-TECH, Pisa, Italy, 1-2 October 2022. [Talk]