Optimized poly(methyl methacrylate)-mediated graphene-transfer process for fabrication of high-quality graphene layer

Abstract

Graphene grown on a copper (Cu) substrate by chemical vapor deposition (CVD) is typically required to be transferred to another substrate for the fabrication of various electrical devices. PMMA-mediated wet process is the most widely used method for CVD-graphene-transfer. However, PMMA residue and wrinkles that inevitably remain on the graphene surface during the transfer process are critical issues degrading the electrical properties of graphene. In this paper, we report on a PMMA-mediated graphene-transfer method that can effectively reduce the density and size of the PMMA residue and the height of wrinkles on the transferred graphene layer. We found out that acetic acid is the most effective PMMA stripper among the typically used solutions to remove the PMMA residue. In addition, we observed that an optimized annealing process can reduce the height of the wrinkles on the transferred graphene layer without degrading the graphene quality. The effects of the suggested wet transfer process were also investigated by evaluating the electrical properties of field-effect transistors fabricated on the transferred graphene layer. The results of this work will contribute to the development of fabrication processes for high-quality graphene devices, given that the transfer of graphene from the Cu substrate is essential process to the application of CVD-graphene.

Corrosion Behavior of Zinc–Nickel and Graphene Layered Structures on Steel Substrates

“…Copper foil with graphene and PMMA was annealed to verify that the particulate clusters on the graphene surface were not associated with surface contamination during the transfer process. The AFM topography and phase imaging of the annealed copper (Figure e, f, respectively) show similar clusters of the same size; those clusters are attributed to PMMA residues that could not be completely removed …”

Effect of Graphene Doping Level near the Metal Contact Region on Electrical and Photoresponse Characteristics of Graphene Photodetector

“…These impurities induce unwanted doping on graphene, thereby resulting in a positive shift of Dirac voltage [28]. The 150 • C-annealing process is commonly used to evaporate moisture from graphene, and the 300 • C-annealing process is known to effectively remove polymer residue on graphene [29,30]. ), whereas the graphene photodetectors reannealed at 300 • C had a Dirac voltage close to 0 V. This indicated that the 150 • C annealing evaporated moisture and the 300 • C annealing effectively removed the polymer residue, which is critical for the practical applications with a low operating voltage of graphene photodetectors.…”

“…A schematic image of the graphene photodetector with various channel lengths is shown in the bottom of Figure 1 a. This annealing process has been widely used to remove surface impurities (PMMA residue, photoresist residue and moisture), which act as p-type dopants [ 28 , 29 , 30 ]. These impurities induce unwanted doping on graphene, thereby resulting in a positive shift of Dirac voltage [ 28 ].…”

“…These impurities induce unwanted doping on graphene, thereby resulting in a positive shift of Dirac voltage [ 28 ]. The 150 °C-annealing process is commonly used to evaporate moisture from graphene, and the 300 °C-annealing process is known to effectively remove polymer residue on graphene [ 29 , 30 ]. Figure 1 b shows two sets of transfer characteristics (I D –V G ) of the graphene photodetectors measured at a constant drain-source bias (V D = 0.1 V).…”

Flexible transparent graphene laminates via direct lamination of graphene onto polyethylene naphthalate substrates

“…[14][15][16] This has been tackled by optimizations using chemical methods to remove such residues and improve graphene performance. 17 However, avoiding PMMA by directly transferring graphene using transfer techniques could lead to several new advantages for reducing the cost and processing time immensely, in particular for industrial applications. This prospect has generated interest in new ways of direct transfer techniques without PMMA resist.…”