Doping free transfer of graphene using aqueous ammonia flow

Morteza Hassanpour Amiri, Jonas Heidler, Ahmar Hasnain, Saleem Anwar, Hao Lu, Klaus Müllen, Kamal Asadi

Research output: Contribution to journalArticlepeer-review

7 Citations (SciVal)


Doping-free transfer of graphene produced by catalytic chemical vapor deposition (CVD) on copper foil, is still a technical challenge since unintentional doping of the transferred graphene layer yields an uncontrolled shift of Dirac point in graphene-based field-effect transistors (FETs). Typically, CVD graphene is released from the growth template by etching of the template, i.e. copper. During the etching process, ions adhere to the graphene layer resulting in unintentional doping. We demonstrate that washing a CVD graphene layer in an aqueous ammonia flow bath after etching copper, removes the majority of the unintentional dopants. FETs fabricated from graphene after washing in DI-water display a large scattering in Dirac bias with lowered mobility. In contrast, FETs from graphene that is washed in ammonia furnish better performance with high geometrically normalized mobility exceeding 2.4 × 104 cm2 V-1 s-1, balanced transport and a Dirac voltage near zero. We attribute the improved FET behavior to effective removal of the ions with a typical density of 4 × 1012 cm-2 from the graphene layer.

Original languageEnglish
Pages (from-to)1127-1131
Number of pages5
JournalRSC Advances
Issue number2
Publication statusPublished - 2019

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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