Characteristics of Highly Area‐Mismatched Graphene‐to‐Substrate Transfers and the Predictability of Wrinkle Formation in Graphene for Stretchable Electronics

Abstract

profile, these wrinkles can remain even after transfer. [12] Moreover, during the transfer process, the surface height profile of the graphene-Cu surface can create an extra area difference in relation to the projected area. On the other hand, a slight area mismatch between the graphene-Cu and transfer substrate can be used to produce an ultra-flat graphene transfer. [13] In order to achieve this, we need long-wavelength, small amplitude corrugations or roughness (low profile morphological conditions) or ultra-short corrugations in the transfer substrates and/or graphene-Cu substrate. Under these conditions, ultraflattening is achieved by tensile mismatch strain. [13] However, the conventional surface features found in Cu foils such as high-profile rolling lines, high surface steps, and other scratch marks formed during the manufacturing process are at odds with the morphological conditions needed to achieve ultra-flat graphene transfer. The objective of highly area-mismatched graphene transfer is mainly focused on avoiding defects, such as cracks, during the transfer process rather than achieving especially smooth transferred graphene film. The indirect transfer technique is well suited for transferring graphene from uneven Cu surfaces because it protects the graphene with a poly(methyl methacrylate) (PMMA) layer during the transfer process and provides structural stability over a large area while mitigating against the defects in the nanoscale Cu-graphene substrate surface as it is moved to an arbitrary substrate. [12-14] The phenomenon was previously described as the formation of surface wrinkles that occur due to the initial surface corrugation conditions of the Cu-graphene substrate. [12,15] Currently, existing graphene-based stretchable electrodes have mainly focus on substrate-controlled designs; stretchable 2D designs based on an etching or selective growth technique or 3D stretchable designs with a supporting top layer. [16-21] The main concept of supporting electrical conductivity under stretchable conditions includes the use of a compressively strained electrode for stretching applications where the electrode becomes unstrained without structural damage when the electrode is in its stretched state. [18,21] Graphene is an extraordinarily good fit for such applications because of its superior flexibility and its mechanical stability as a nanomaterial.

Transport Property of Wrinkled Graphene Nanoribbon Tuned by Spin-Polarized Gate Made of Vanadium-Benzene Nanowire

“…Governed by the supernal flexibility of graphene, using the surface topographical corrugations like wrinkles [24,25], ripples [26][27][28][29][30][31][32][33], folds [34], or crumples [35][36][37][38] to exploit exceptional properties is an amazing technique in experiments. In particular, high-quality conformal wrinkles in graphene can be controllably fabricated with expected orientations, wavelengths, and amplitudes by using various simple methods, which is of paramount importance for potential applications in flexible electrodes, sensors, and actuators [39][40][41][42][43][44].…”