Performance Improvement of Residue-Free Graphene Field-Effect Transistor Using Au-Assisted Transfer Method

We report a novel graphene transfer technique for fabricating graphene field-effect transistors (FETs) that avoids detrimental organic contamination on a graphene surface. Instead of using an organic supporting film like poly(methyl methacrylate) (PMMA) for graphene transfer, Au film is directly deposited on the as-grown graphene substrate. Graphene FETs fabricated using the established organic film transfer method are easily contaminated by organic residues, while Au film protects graphene channels from these contaminants. In addition, this method can also simplify the device fabrication process, as the Au film acts as an electrode. We successfully fabricated graphene FETs with a clean surface and improved electrical properties using this Au-assisted transfer method.

Graphene Transfer: A Physical Perspective

Graphene, synthesized either epitaxially on silicon carbide or via chemical vapor deposition (CVD) on a transition metal, is gathering an increasing amount of interest from industrial and commercial ventures due to its remarkable electronic, mechanical, and thermal properties, as well as the ease with which it can be incorporated into devices. To exploit these superlative properties, it is generally necessary to transfer graphene from its conductive growth substrate to a more appropriate target substrate. In this review, we analyze the literature describing graphene transfer methods developed over the last decade. We present a simple physical model of the adhesion of graphene to its substrate, and we use this model to organize the various graphene transfer techniques by how they tackle the problem of modulating the adhesion energy between graphene and its substrate. We consider the challenges inherent in both delamination of graphene from its original substrate as well as relamination of graphene onto its target substrate, and we show how our simple model can rationalize various transfer strategies to mitigate these challenges and overcome the introduction of impurities and defects into the graphene. Our analysis of graphene transfer strategies concludes with a suggestion of possible future directions for the field.

How Surface Tension Matters in Polymer-Free Graphene Transfer

Objectives The main goal of this work is to achieve a direct transfer of graphene and examine the exact effect of surface tension (ST) on graphene during this type of transfer. Methods To reach this target, we designed a specific transfer container with two-sided ports to facilitate replacing liquids underneath graphene and monitor the effect of ST. We prepared liquids with various STs by mixing pure DI-water with different ratios of isopropanol (IPA). Results Our results indicate that high ST does not break the graphene structure if graphene has good quality. Besides, a surface tension gap (STG) can be applied to graphene at a specific level without damaging the graphene monolayer. Comparing those results to the defective graphene features after applying high ST and varied STGs confirms that standing high ST and STG can be considered a key feature of good quality graphene. Conclusion Thus, good quality graphene can be transferred at high ST (ST of water: 72 dyne/cm) with no sign of structural damage. In addition, this type of graphene can stand STG ≤ 40 dyne/cm. This new understanding of the ST effect on graphene could simplify the current direct transfer techniques and widen the graphene applications by expanding the choices of the target substrates and transfer liquids.