Figure 1

(Color online) Morphology of SiC surfaces during graphitization. (a) Atomic force microscope (AFM) image $\left(26\times 26\mu {\text{m}}^2\right)$ using phase contrast imaging (Ref. 12). Graphene layers (dark gray) are formed at the upper sides (left side in the presented image) of the bunched steps (indicated as SB). A tall bunched step often appears as a black line in an AFM phase image. “Arrow features” and “finger features” are highlighted by the blue and green boxes, respectively. (b) LEEM image of the “arrow features” $\left(4.2\times 4.2\mu {\text{m}}^2\right)$ using incident electrons of $E_{vac}+2.85\text{eV}$, where $E_{vac}$ is the vacuum level. The dark gray regions consist of a graphene monolayer, and the light gray regions are buffer layer. (c) STM image ($1.8\times 1.05\mu {\text{m}}^2$, tip bias of $-2.5\text{V}$, and tunneling current of 0.2 nA) with the cross section along the yellow line. (d) Red and black hatched boxes in (d) illustrate a proposed step structure with the cross sections of graphene (1 ML) and buffer layer (0 ML) regions with their thicknesses of 0.33 and 0.25 nm, respectively (Ref. 22).Reuse & Permissions

Figure 2

(Color online) Schematic of the formation of an arrow feature. The insets show static LEEM images of SiC bilayer steps at similar stages of evolution. LEEM images are (c) $2\times 2\mu {\text{m}}^2$, (d) $2\times 2\mu {\text{m}}^2$, and (e) $4\times 2\mu {\text{m}}^2$.Reuse & Permissions

Figure 3

(Color online) (a) The calculated surface C adatom concentration map derived by solving the time-dependent diffusion equation for the arrow geometry. (b) Profile of the carbon flux along the shaft of the arrow feature.Reuse & Permissions

Figure 4

(Color online) Step flow growth of graphene. (a) and (b) Growth observed in LEEM $\left(3.5\times 3.5\mu {\text{m}}^2\right)$. The dark gray regions consist of $>2\text{ML}$ of graphene, the medium gray regions are graphene monolayer, and the light gray regions are buffer layer. (c) Schematic of the step flow. Triple bilayers of SiC (dotted lines) are transformed into a single graphene layer. (d) The cross section of the STM image in (e). The step bunch and the lower terraces are omitted. Red and black hatched boxes and white boxes indicate 1 ML graphene, buffer layer, and SiC bilayer, respectively (Ref. 28). (e) STM image ($4\times 2\mu {\text{m}}^2$, tip bias of 1.7 V, and tunneling current of 0.1 nA) of the sample with monolayer and bilayer graphene growing from the step bunch.Reuse & Permissions