Camara et al. Nanoscale Research Letters 2011, 6:141 http://www.nanoscalereslett.com/content/6/1/141 N A N O E X P R E S S Open Access Multidimensional characterization, Landau levels and Density of States in epitaxial graphene grown on SiC substrates Nicolas Camara1, Benoit Jouault1*, Bilal Jabakhanji1, Alessandra Caboni2, Antoine Tiberj1, Christophe Consejo1, Philipe Godignon2, Jean Camassel1 Abstract Using high-temperature annealing conditions with a graphite cap covering the C-face of, both, on axis and 8° off- axis 4H-SiC samples, large and homogeneous single epitaxial graphene layers have been grown. Raman spectroscopy shows evidence of the almost free-standing character of these monolayer graphene sheets, which was confirmed by magneto-transport measurements. On the best samples, we find a moderate p-type doping, a high-carrier mobility and resolve the half-integer quantum Hall effect typical of high-quality graphene samples. A rough estimation of the density of states is given from temperature measurements. Introduction It is now widely accepted that graphene-based devices are promising candidates to complement silicon in the future generations of high-frequency microelectronic devices. To this end, the most favourable technique to produce graphene for industrial scale applications seems to be epitaxial graphene (EG) growth. This can be done by chemical vapour deposition on a metal [1,2] or by heating a SiC wafer up to the graphitisation temperature [3-6]. In the first case, the disadvantage is the need to transfer the graphene film on an insulating wafer. In the second case, the SiC wafer plays the role of the insulat- ing substrate without any need for further manipulation. Of course, to be suitable for the microelectronics indus- try, these EG layers must be continuous and homoge- neous at the full wafer scale or, at least, on surfaces large enough to process devices. On the Si-face of 6H or 4H SiC substrates, graphitisa- tion at high temperature in an Ar atmosphere close to atmospheric pressure shows promising results for on-axis substrates. In this way, single-layer epitaxial graphene (SLEG) has already been grown at the full wafer scale [7,8] but an open issue remains the 6√3 SiC surface * Correspondence: jouault@ges.univ-montp2.fr 1Laboratoire Charles Coulomb, UMR 5221 CNRS-UM2, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France Full list of author information is available at the end of the article reconstruction which is a C-rich buffer monolayer on top of the SiC substrate. The first “real” graphene layer on top of this buffer layer is strained, not at all free-standing, strongly coupled to the C-rich buffer, heavily n-type doped, with a low-carrier mobility. On the contrary, on the C-face of the same SiC substrates, there is no need of a C-rich buffer layer at the interface before growing the first graphene layer [9-12]. In this way, the mobility could reach 30,000 cm2/V s in the work of Ref. [13]. For a long time, whatever the growth technique, the uniformity and quality of the EG was not good enough to find evidence of the so-called “half integer” quantum Hall effect (QHE). However, recently, large SLEG areas have been produced on the C-face of on-axis SiC sub- strates and, on such monolayer graphene, the carriers were holes with mobility close to the one found in mechanically exfoliated graphene films on SiO2/Si [14]. Consequently, the QHE could be demonstrated [15]. This shows clearly the advantage and quality of SLEG grown on the on-axis C-face of a SiC wafer over the on- axis Si-face. However, for further integration of gra- phene with current SiC technology, 8° off-axis substrates should be also considered since they constitute the stan- dard in modern SiC industry [16]. In this work, we compare the results of graphene growth on semi-insulating, on axis and and 8° off-axis, 4H-SiC substrates. The quality, uniformity and size of © 2011 Camara et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.