High-quality graphene on SiC(000$\overline{1}$) formed through an epitaxial TiC layer

The formation of large-area homogeneous graphene on a C-terminated SiC (000$\overline{1}$) surface was achieved via decomposition of the SiC (000$\overline{1}$) surface covered with an ultrathin but much more stable TiC layer than the reactive SiC(000$\overline{1}$). By heating the SiC (000$\overline{1}$) surface with a mixed powder of TiO${}_2$ and carbon at 1500–1550 °C in vacuum, an extremely homogeneous, epitaxial 0.75-nm-thick TiC(111) layer was grown on the SiC(000$\overline{1}$) surface over a millimeter-scale area. Graphitization of the TiC-masked SiC surface led to the growth of high-quality graphene layers, which consist of TiC- and SiC-derived carbon. High-resolution transmission electron microscopy revealed the presence of disordered stacking of graphene layers on SiC through an amorphous layer at the interface. This unique method will promise further progress of relatively high carrier mobility of graphene formed on the SiC (000$\overline{1}$) surface.

Figure 1

TEM image of graphene layers formed on the facets grown around a TiC particle annealed at 1700 °C in a vacuum.

Figure 2

Projected sites of (a) Si atoms (or C atoms) on 6H-SiC(000$\overline{1}$) and (b) Ti atoms (or C atoms) on TiC(111).

Figure 3

TiC blocks and layer formed on the SiC(000$\overline{1}$) at 1600–1650 °C for 1 h. (a) SEM image of the TiC connected blocks. (b), (c) TEM images of the TiC blocks and the electron diffraction pattern. (d) The high-resolution TEM image, (e) the electron diffraction pattern, and (f) the FFT pattern of the TiC layer formed on the SiC(000$\overline{1}$) face.

Figure 4

Ultrathin TiC layer formed on the SiC(000$\overline{1}$) C-face at 1500–1550 °C for 1 h. (a) Low-magnification TEM image and (b) high-resolution TEM image of the ultrathin TiC layer on SiC observed along the cross-sectional direction. AFM images of (c) the mechanically polished surface of the as-received SiC(000$\overline{1}$) C-face and (d) the ultrathin TiC-layered SiC surface. Optical microscopy images of (e) uncontrolled and (f) well-controlled TiC-layered SiC surfaces of millimeter size.

Figure 5

EELS mapping images of the TiC/SiC substrate. (a) The bright field TEM image; (b) C mapping; (c) Ti mapping.

Figure 6

TEM images of homogeneous high quality graphene layers formed by graphitization of the TiC/SiC(000$\overline{1}$) C-face at 1500 °C (a) for 0.5 and (b) for 1.5 h in Ar gas at 6 atm pressure. (c) AFM topographic image with the cross-sectional cut along the line A-B, and (d) the corresponding phase image of the same sample shown in (b). (c) Heights of the steps sandwiched by red, green, and blue parallel lines were 0.93, 1.55, and 1.51 nm, respectively. (e) Raman spectrum at 532 nm for the graphene layers shown in (b), (c), and (d).

Figure 7

(a) High-resolution TEM image of the graphene formed from the ultrathin TiC layer/SiC(000$\overline{1}$) C-face observed along graphene [11$\overline{2}$0] direction//SiC[1$\overline{1}$00]. (b) FFT pattern of the disordered stack-structured graphene layers on SiC.