Effects of polymethylmethacrylate-transfer residues on the growth of organic semiconductor molecules on chemical vapor deposited graphene

Abstract

Scalably grown and transferred graphene is a highly promising material for organic electronic applications, but controlled interfacing of graphene thereby remains a key challenge. Here, we study the growth characteristics of the important organic semiconductor molecule para-hexaphenyl (6P) on chemical vapor deposited graphene that has been transferred with polymethylmethacrylate (PMMA) onto oxidized Si wafer supports. A particular focus is on the influence of PMMA residual contamination, which we systematically reduce by H2 annealing prior to 6P deposition. We find that 6P grows in a flat-lying needle-type morphology, surprisingly independent of the level of PMMA residue and of graphene defects. Wrinkles in the graphene typically act as preferential nucleation centers. Residual PMMA does however limit the length of the resulting 6P needles by restricting molecular diffusion/attachment. We discuss the implications for organic device fabrication, with particular regard to contamination and defect tolerance.

Growth of Large Crystalline Grains of Vanadyl‐Phthalocyanine without Epitaxy on Graphene

“…However, the island sizes are smaller due to the effects of the residue from the transfer process (see Section 7, Supporting Information), which is known to infl uence the growth of OSC structures on graphene. [ 32 ] Figure 3 b shows a low-dose (see Section 8, Supporting Information, for details of low-dose procedures), selected-area electron diffraction pattern from the island highlighted in white in Figure 3 a. The pattern shows sharp diffraction spots that are indicative of crystalline VOPc and are consistent with the molecules being ordered close to the [132] direction relative to the graphene surface, as previously suggested by the XRD measurements.…”

“…[ 27 ] Understanding how OSCs interact with graphene will be critical for further incorporation, and much work has been done on the graphene/OSC interface. [28][29][30][31][32][33] Recent work has shown how van der Waals epitaxy can result in the growth of large, highly crystalline OSC domains on graphene with improved device performance. [ 30,31 ] This epitaxial growth requires suffi cient interaction between graphene and the molecule, and hence is limited to a subset of OSCs.…”

On-surface derivatisation of aromatic molecules on graphene: the importance of packing density

“…16 More specifically, we found that graphene with polymer residues from the transfer process produces a lower packing density molecular layer than that of graphene that has been annealed to remove these residues, similar to what has been described by other groups. 17,18 In this communication,…”

Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

“…This challenge is particularly highlighted by the many proposed (opto-)electronic graphene devices, starting with simple gated graphene field effect device structures, for which the graphene performance is found to be highly sensitive to the presence of any contaminants [16][17][18][19]. Most polymer [20][21][22][23][24] and metal [25,26] layers used as temporary mechanical supports during graphene transfer have been shown to leave residues on graphene after removal, degrading its electronic properties [12,27,28]. Other common contaminants include lithographic resists, organic solvents, etching products and ambient air [29], all of which can for instance unintentionally dope the graphene (generally p-type [17]) and cause hysteresis in field effect devices [30].…”