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

Författare:
  • Konstantin V. Emtsev
  • Alexei Zakharov
  • Camilla Coletti
  • Stiven Forti
  • Ulrich Starke
Publiceringsår: 2011
Språk: Engelska
Sidor:
Publikation/Tidskrift/Serie: Physical Review B
Volym: 84
Nummer: 12
Dokumenttyp: Artikel
Förlag: American Physical Society

Sammanfattning

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 (6 root 3 x 6 root 3)R30 degrees reconstructed buffer layer on SiC(0001) is converted into quasi-free-standing monolayer graphene after Ge intercalation and shows the characteristic graphene pi 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.

Disputation

Nyckelord

  • Physics and Astronomy

Övriga

Published
Yes
  • ISSN: 1098-0121

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