| 1. |
- Karlsson, Linda, et al.
(författare)
-
Graphene on graphene formation from PMMA residues during annealing
- 2017
-
Ingår i: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 137, s. 191-194
-
Tidskriftsartikel (refereegranskat)abstract
- PMMA is a common support material for transferring graphene between substrates. However, PMMA residues typically remain on the graphene sheet after the transfer process. A high temperature annealing process is commonly applied to reduce the amount of PMMA residues. It is also known that high temperature annealing of PMMA causes the PMMA to graphitize, which has been used as a method to synthesize graphene on metal substrates. In this letter we show the development of additional graphene layers during high temperature annealing, which occurs on a single, clean, graphene sheet. The additional graphene is nucleated from the decomposition products of PMMA residues. (C) 2017 Elsevier Ltd. All rights reserved.
|
|
| 2. |
- Karlsson, Linda, et al.
(författare)
-
Residue reduction and intersurface interaction on single graphene sheets
- 2016
-
Ingår i: Carbon. - : Pergamon Press. - 0008-6223 .- 1873-3891. ; 100, s. 345-350
-
Tidskriftsartikel (refereegranskat)abstract
- Large regions of pristine graphene are essential to applications which rely on the ideal graphene properties. Common methods for transferring chemical vapour deposition grown graphene to suitable substrates leaves metal oxide particles and poly(methyl methacrylate) (PMMA) residues on opposing surfaces, which degrade the properties. A common method to reduce the residues include annealing in vacuum or in argon, however, residues remain on the graphene sheet. The present investigation reports on the metal oxide particle ripening and PMMA decomposition on a single graphene sheet during in-situ annealing up to 1300 degrees C in a transmission electron microscope. It is shown that the PMMA residues are increasingly reduced at elevated temperatures although the reduction is strongly correlated to the metal oxide particle coverage on the opposing graphene surface. This is shown to occur as a consequence of an electrostatic interaction between the residues and that this prevents the establishment of large clean areas. (C) 2016 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Ta, Huy Q., et al.
(författare)
-
Single Cr atom catalytic growth of graphene
- 2018
-
Ingår i: Nano Reseach. - : TSINGHUA UNIV PRESS. - 1998-0124 .- 1998-0000. ; 11:5, s. 2405-2411
-
Tidskriftsartikel (refereegranskat)abstract
- Single atoms are the ultimate minimum size limit for catalysts. Graphene, as an exciting, ultimately thin (one atom thick) material can be imaged in a transmission electron microscope with relatively few imaging artefacts. Here, we directly observe the behavior of single Cr atoms in graphene mono- and di-vacancies and, more importantly, at graphene edges. Similar studies at graphene edges with other elemental atoms, with the exception of Fe, show catalytic etching of graphene. Fe atoms have been shown to both etch and grow graphene. In contrast, Cr atoms are only observed to induce graphene growth. Complementary theoretical calculations illuminate the differences between Fe and Cr, and confirm single Cr atoms as superior catalysts for sp(2) carbon growth.
|
|
