Issue 2, 2020

Doping free transfer of graphene using aqueous ammonia flow


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.

Graphical abstract: Doping free transfer of graphene using aqueous ammonia flow

Article information

Article type
26 Aug 2019
06 Dec 2019
First published
06 Jan 2020
This article is Open Access
Creative Commons BY license

RSC Adv., 2020,10, 1127-1131

Doping free transfer of graphene using aqueous ammonia flow

M. Hassanpour Amiri, J. Heidler, A. Hasnain, S. Anwar, H. Lu, K. Müllen and K. Asadi, RSC Adv., 2020, 10, 1127 DOI: 10.1039/C9RA06738H

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