Strain, Bubbles, Dirt, and Folds: A Study of Graphene Polymer‐Assisted Transfer

Abstract

For many applications, in particular in electronics, where chemical vapor deposited (CVD) graphene is used, it needs to be transferred from the growth substrate to the device substrate, generally employing a polymer film as a support layer. This process step is crucial for the overall integrity and electronic performance of the graphene. In this work we will investigate the effects of the transfer using various polymers with atomic force, Raman spectroscopy and X‐ray photoelectron spectroscopy combined with field dependent transport measurements to build up a complete picture regarding the morphology, structural integrity and electrical performance of CVD graphene. Further, we introduce nitrocellulose based polymer alternatives to the most commonly used poly(methyl methacrylate) resist, outperforming the latter in most respects.

Molecular Caging of Graphene with Cyclohexane: Transfer and Electrical Transport

“…A typical bad AFM image of graphene transferred to a silicon wafer by PMMA-assisted method has multiple features that correspond to wrinkles, PMMA residues, and dust particles. 8,9,11 PMMA-transferred graphene has multiple topological features (Figure 3b). Those could be interpreted as wrinkles or as polymer residues segregated on the grain boundaries of graphene.…”

“…2−6 Because of their macromolecular structures, polymers can hardly be removed from the graphene surface: 7−9 they irreversibly adsorb and modify the chemical and physical properties of graphene. 10,11 Instead of using polymers, so-called polymer-free transfer techniques use special frames and holders to keep the sheet integrity of graphene.…”

Spatially Resolved Covalent Functionalization Patterns on Graphene

“…The mild reaction conditions allow introduction of covalently dynamic linkages,w hichc an serve as reversible labels for surface-or graphene-enhanced Raman spectroscopyc haracterization of the patterns prepared. [24][25][26] Using covalent modification for spatially resolved functionalization typically relies on preventing contact of the reagents with graphene,t hus implying the use of ar esist mask [27] or controlled deposition [28,29] at the nanoscale,w hich either adds more steps (with concomitant contamination [30] ) or severely limits the processing speed, respectively.P hotochemical reactions represent au nique alternative to the abovementioned two approaches [31] because photochemistry responds to illumination patterns without the need for aresist or spatially confined reagent deposition.Thec ritical challenge for the surface functionalization of the 2D materials is unambiguous characterization of the reaction products facing the detection and resolution limits of many methods due to the strict monolayer nature of the materials. [7][8][9] Although several approaches for covalent grafting have been reported, [10][11][12][13][14][15] only recently has the advancement towards specific applications revealed the need for spatially resolved methods that would provide patterned surface functionalization on the 2D material, [16][17][18] aiming at sophisticated sensor arrays or device mass production.…”

“…[19] This non-trivial task has been approached from several directions,u sing for instance photolithography, [20] dip-pen lithography [21][22][23] or various writing techniques. [24][25][26] Using covalent modification for spatially resolved functionalization typically relies on preventing contact of the reagents with graphene,t hus implying the use of ar esist mask [27] or controlled deposition [28,29] at the nanoscale,w hich either adds more steps (with concomitant contamination [30] ) or severely limits the processing speed, respectively.P hotochemical reactions represent au nique alternative to the abovementioned two approaches [31] because photochemistry responds to illumination patterns without the need for aresist or spatially confined reagent deposition.…”

Development and characterization of graphene-based electronic devices

“…The simplest ones are based on residue minimization [49][50][51][52] or its removal through thermal annealing [53]. Some other upgrades of higher complexity are the selection of the transfer region on the target substrate [40,[54][55][56], the recovery of the growth substrate for its reutilization [57][58][59] by using the named bubbling transfer, or a film handling enhancement that minimizes the mechanical damage on the graphene, either by adding a rigid carrier [5,[60][61][62][63][64] or by using capillarity effects [65] or electrostatic forces [66,67] that restrict the type of target substrate.…”