Layer-number determination in graphene on SiC by reflectance mapping
2014 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 77, 492-500 p.Article in journal (Refereed) Published
We report a simple, handy and affordable optical approach for precise number-of-layers determination of graphene on SiC based on monitoring the power of the laser beam reflected from the sample (reflectance mapping) in a slightly modified micro-Raman setup. Reflectance mapping is compatible with simultaneous Raman mapping. We find experimentally that the reflectance of graphene on SiC normalized to the reflectivity of bare substrate (the contrast) increases linearly with similar to 1.7% per layer for up to 12 layers, in agreement with theory The wavelength dependence of the contrast in the visible is investigated using the concept of ideal fermions and compared with existing experimental data for the optical constants of graphene. We argue also that the observed contrast is insensitive to the doping condition of the sample, as well as to the type of sample (graphene on C- or Si-face of 4H or 6H SiC, hydrogen-intercalated graphene). The possibility to extend the precise layer counting to similar to 50 layers makes reflectivity mapping superior to low-energy electron microscopy (limited to similar to 10 layers) in quantitative evaluation of graphene on the C-face of SiC. The method is applicable for graphene on other insulating or semiconducting substrates.
Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 77, 492-500 p.
IdentifiersURN: urn:nbn:se:liu:diva-110689DOI: 10.1016/j.carbon.2014.05.054ISI: 000340689400054OAI: oai:DiVA.org:liu-110689DiVA: diva2:749471
Funding Agencies|GRAPHIC-RF project within the EuroGRAPHENE program of the European Science Foundation (ESF); EPIGRAT project within the EuroGRAPHENE program of the European Science Foundation (ESF)2014-09-242014-09-192014-11-04