Ambipolar doping in quasifree epitaxial graphene on SiC(0001) controlled by Ge intercalation

Konstantin V. Emtsev, Alexei A. Zakharov, Camilla Coletti, Stiven Forti, and Ulrich Starke
Phys. Rev. B 84, 125423 – Published 9 September 2011
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Abstract

The electronic structure of decoupled graphene on SiC(0001) can be tailored by introducing atomically thin layers of germanium at the interface. The electronically inactive (63×63)R30 reconstructed buffer layer on SiC(0001) is converted into quasi-free-standing monolayer graphene after Ge intercalation and shows the characteristic graphene π bands as displayed by angle-resolved photoelectron spectroscopy. Low-energy electron microscopy (LEEM) studies reveal an unusual mechanism of the intercalation in which the initial buffer layer is first ruptured into nanoscopic domains to allow the local in-diffusion of germanium to the interface. Upon further annealing, a continuous and homogeneous quasifree graphene film develops. Two symmetrically doped (n- and p-type) phases are obtained that are characterized by different Ge coverages. They can be prepared individually by annealing a Ge film at different temperatures. In an intermediate-temperature regime, a coexistence of the two phases can be achieved. In this transition regime, n-doped islands start to grow on a 100-nm scale within p-doped graphene terraces as revealed by LEEM. Subsequently, the n islands coalesce but still adjacent terraces may display different doping. Hence, lateral p-n junctions can be generated on epitaxial graphene with their size tailored on a mesoscopic scale.

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  • Received 1 July 2011

DOI:https://doi.org/10.1103/PhysRevB.84.125423

©2011 American Physical Society

Authors & Affiliations

Konstantin V. Emtsev1,*, Alexei A. Zakharov2, Camilla Coletti1,†, Stiven Forti1, and Ulrich Starke1

  • 1Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
  • 2MAXLab, Lund University, S-22100 Lund, Sweden

  • *k.emtsev@fkf.mpg.de; [http://www.fkf.mpg.de/ga]
  • Present address: Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, 56127 Pisa, Italy.

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Issue

Vol. 84, Iss. 12 — 15 September 2011

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