Manipulation of oxygen atoms on epitaxial graphene by a variable-temperature scanning tunneling microscope

Graphene, consisting of atomically thin honeycomb lattice of sp2-bonded carbon atoms, is one of the most popular 2D materials. To modify electronic properties of graphene, one can chemically functionalize graphene with hydrogen [1,2], fluorine [3], and oxygen [4]. Chemically homogeneous oxidation of epitaxial graphene was realized by depositing atomic oxygen in ultrahigh vacuum (UHV), suggesting a new possibility of nanopatterning on graphene oxide [5]. In this talk, we would like to show electronic properties and atomic structures of oxidized epitaxial graphene, which we measured using scanning tunneling microscopy (STM). To prepare oxidized epitaxial graphene, we generated atomic oxygen beams by passing oxygen molecules through a hot Ir capillary. Then we deposited atomic oxygen beams on the epitaxial graphene substrate. Once the atomic oxygen was identified, we brought a STM tip on it and applied a voltage pulse to manipulate it. This manipulation of oxygen atoms on epitaxial graphene allows us to tailor local electronic properties of graphene in atomic scale. Furthermore, to minimize thermal drift in temperature-dependent STM measurements, we constructed a variable-temperature STM with a small piezoelectric motor called KoalaDrive [6], which has been working well at low temperature. [1] D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. Boukhvalov, M. I. Katsnelson, A. K. Geim, and K. S. Novoselov, Science 323, 610 (2009). [2] R. Balog, B. Jørgensen, L. Nilsson, M. Andersen, E. Rienks, M. Bianchi, M. Fanetti, E. Lægsgaard, A. Baraldi, S. Lizzit, Z. Sljivancanin, F. Besenbacher, B. Hammer, T. G. Pedersen, P. Hofmann, and L. Hornekær, Nat. Mater. 9, 315 (2010). [3] F. Karlický, K. Kumara Ramanatha Datta, M. Otyepka, and R. Zbořil, ACS Nano 7, 6434 (2013). [4] D. R. Dreyer, S. Park, C. W. Bielawski, and R. S. Ruoff, Chem. Soc. Rev. 39, 228 (2010). [5] M. Z. Hossain, J. E. Johns, K. H. Bevan, H. J. Karmel, Y. T. Liang, S. Yoshimoto, K. Mukai, T. Koitaya, J. Yoshinobu, M. Kawai, A. M. Lear, L. L. Kesmodel, S. L. Tait, and M. C. Hersam, Nat. Chem. 4, 305 (2012). [6] V. Cherepanov, P. Coenen, and B. Voigtländer, Rev. Sci. Instrum. 83, 23703 (2012).2