Camara et al. Nanoscale Research Letters 2011, 6:141 http://www.nanoscalereslett.com/content/6/1/141 the growth products will be compared using optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spec- troscopy (μR). Then, Hall effect measurements will be done at different temperature in order to extract the density of states in the epitaxial monolayers. Graphene growth, microscopy and Raman studies To produce SLEG, in both cases of on axis and 8° off-axis SiC substrates, we used the recipes of Ref. [12]. On the on-axis material, this produces long, self-ordered, gra- phene ribbons which are typically 5 μm wide and several 100 μm long. This has been described at length in the work of Ref. [16]. On the off-axis substrates, this resulted also on SLEG islands but the morphology is completely different This is shown in Figure 1. Instead of narrow rib- bons, after 30 min graphitisation at 1700°C, large SLEG islands can be obtained which can reach 300 μm long and 50 μm wide for the biggest ones. See Figure 1a and 1b. They can have a trapezoidal or triangular shape, see Figure 1a-c and 1f and, usually, nucleate from a defect on the surface. See Figure 1e and 1f. This may be either an Page 2 of 6 unintentional particle remaining on the surface, a crystal- lographic defect such as a threading dislocation or a sim- ple scratch made by a diamond tip. Whatever the origin, the growth starts from one nucleating centre and expands in a two-dimension carpet-like way. All resulting triangles are then self-oriented, with the longest side following the (11-20) plane direction. In Figure 2a we show a typical AFM image of such a SLEG islands. When zooming, wrinkles become clearly visible in Figure 2 and show evidence of the continuity and strain-free character of the monolayers. Below the graphene islands, the step-bunched areas of the SiC sur- face are also clearly visible in both SEM and AFM pic- tures. The corresponding terraces are typically 100 nm wide and less than 2 nm high. A last evidence of the fact that the first layer of graphene is not coupled with the substrate and continuous despite the step-bunched surface is the facility with which we can remove the SLEG layer with an AFM tip. The result presented with the AFM picture of Figure 2c demonstrates the almost free-standing and continuous character of the grown SLEG. Figure 1 SEM images of a monolayer graphene islands grown on the C-face of an 8° off-axis 4H-SiC substrate. (a, b) Images of the largest homogeneous SLEG islands, (c) early growth, (d) zoomed image with visible wrinkles, (e, f) example of starting nucleation point by a surface defect with step bunching clearly visible in (f).