Hassanpour Amiri Morteza, Heidler Jonas, Hasnain Ahmar, Anwar Saleem, Lu Hao, Müllen Klaus, Asadi Kamal
Max-Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
School of Chemical & Materials Engineering, National University of Sciences & Technology Sector H-12 Islamabad Pakistan.
RSC Adv. 2020 Jan 6;10(2):1127-1131. doi: 10.1039/c9ra06738h. eCollection 2020 Jan 2.
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, 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 × 10 cm V s, 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 × 10 cm from the graphene layer.
通过催化化学气相沉积（CVD）在铜箔上制备的石墨烯进行无掺杂转移，仍然是一项技术挑战，因为转移的石墨烯层的无意掺杂会导致基于石墨烯的场效应晶体管（FET）中狄拉克点发生不受控制的偏移。通常，CVD石墨烯通过蚀刻生长模板铜从模板上释放出来。在蚀刻过程中，离子附着在石墨烯层上，导致无意掺杂。我们证明，在蚀刻铜之后，在氨水流浴中洗涤CVD石墨烯层，可以去除大部分无意掺杂剂。在去离子水中洗涤后的石墨烯制成的FET在狄拉克偏压下表现出较大的散射，迁移率降低。相比之下，在氨水中洗涤的石墨烯制成的FET具有更好的性能，几何归一化迁移率超过2.4×10 cm²V⁻¹s⁻¹，具有平衡的输运特性，且狄拉克电压接近零。我们将FET性能的改善归因于从石墨烯层有效去除了典型密度为4×10¹² cm⁻²的离子。
