2012 Volume 10 Pages 292-296
We have developed a low-energy electron diffraction (LEED) apparatus using field emission (FE) from scanning tunneling microscopy (STM) tips. Tips fabricated by field-assisted H2O etching enabled us to observe LEED patterns of few layer graphene grown on SiC(0001) reproducibly. The obtained hexagonal patterns showed a bias dependency and those obtained at sample biases of 93 V, 56 V, and 28 V were interpreted as patterns derived from the graphene, the SiC(0001) substrate, and a (6√3 × 6√3)R30° buffer layer, respectively. The analysis of Ewald sphere construction indicated that the opening angles of FE from the tip could be deduced directly from the LEED patterns, and their experimentally obtained value was ∼13°. From the opening angle of FE and the dataset of tip-to-sample distances, the irradiated areas were estimated at 350 nmφ when the sample bias was 100 V. [DOI: 10.1380/ejssnt.2012.292]
