Abstract
Solid substrates often induce non-uniform strain and doping in graphene monolayer, therefore altering the intrinsic properties of graphene, reducing its charge carrier mobilities and, consequently, the overall electrical performance. Here, we exploit confocal Raman spectroscopy to study graphene directly free-floating on the surface of water, and show that liquid supports relief the preexisting strain, have negligible doping effect and restore the uniformity of the properties throughout the graphene sheet. Such an effect originates from the structural adaptability and flexibility, lesser contamination and weaker intermolecular bonding of liquids compared to solid supports, independently of the chemical nature of the liquid. Moreover, we demonstrate that water provides a platform to study and distinguish chemical defects from substrate-induced defects, in the particular case of hydrogenated graphene. Liquid supports, thus, are advantageous over solid supports for a range of applications, particularly for monitoring changes in the graphene structure upon chemical modification.
Highlights
Solid substrates often induce non-uniform strain and doping in graphene monolayer, altering the intrinsic properties of graphene, reducing its charge carrier mobilities and, the overall electrical performance
By applying confocal Raman spectroscopy to chemical vapour deposition (CVD)-grown graphene free-floating at water/air and water/liquid interfaces, we found that graphene supported by liquid(s) undergoes very small to zero strain and doping effect, posing stark contrast with “conventional” solid-supported graphene, known to always be subjected to strain and doping[10,11,12,13,14,15,16,17,18]
Graphene floats when placed on the surface of water due to the density and water surface tension. This property is routinely used when transferring CVD graphene from a catalyst substrate – the graphene/catalyst stack is placed on the surface of an aqueous solution of an etchant until the catalyst is fully dissolved and the graphene sheet remains free-floating at the water/air interface to be transferred further[27,28]
Summary
Solid substrates often induce non-uniform strain and doping in graphene monolayer, altering the intrinsic properties of graphene, reducing its charge carrier mobilities and, the overall electrical performance. We exploit confocal Raman spectroscopy to study graphene directly free-floating on the surface of water, and show that liquid supports relief the preexisting strain, have negligible doping effect and restore the uniformity of the properties throughout the graphene sheet Such an effect originates from the structural adaptability and flexibility, lesser contamination and weaker intermolecular bonding of liquids compared to solid supports, independently of the chemical nature of the liquid. Statistical analysis of graphene Raman peaks showed that the variations of strain and doping values across a graphene sheet are significantly smaller when supported by liquids, owing to more homogeneous and molecularly defined graphene-liquid interface, as opposed to a graphene-solid interface We find that such exceptional stability of the Raman signature of graphene in a liquid environment can be used to characterize changes in the properties of graphene upon hydrogenation, and upon modifying the composition of liquid environment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
