Pattern Pick and Place Method for Twisted Bi- and Multi-Layer Graphene

Abstract

Twisted bi-layer graphene (tBLG) has attracted much attention because of its unique band structure and properties. The properties of tBLG vary with small differences in the interlayer twist angle, but it is difficult to accurately adjust the interlayer twist angle of tBLG with the conventional fabrication method. In this study, we introduce a facile tBLG fabrication method that directly picks up a single-crystalline graphene layer from a growth substrate and places it on another graphene layer with a pre-designed twist angle. Using this approach, we stacked single-crystalline graphene layers with controlled twist angles and thus fabricated tBLG and twisted multi-layer graphene (tMLG). The structural, optical and electrical properties depending on the twist angle and number of layers, were investigated using transmission electron microscopy (TEM), micro–Raman spectroscopy, and gate-dependent sheet resistance measurements. The obtained results show that the pick and place approach enables the direct dry transfer of the top graphene layer on the as-grown graphene to fabricate uniform tBLG and tMLG with minimal interlayer contamination and pre-defined twist angles.

Toward Scalable Growth for Single-Crystal Graphene on Polycrystalline Metal Foil

“…By using a polymethylsiloxane (PDMS) stamp coated with the thermal-releasable polymer layer, which has arrays of micropillars with a diameter of 30 μm and an interval of 30 μm, the Au/graphene seed arrays with uniform spacing can be selectively picked up and released onto the polycrystalline Pt substrate (Figure c,d). The Au thin film prevents graphene seed arrays from direct contact with polymers used in the photolithography and transfer process . After transfer to the growth substrate, organic residues on the substrate were removed using O 2 plasma, and then Au protective layers on graphene seeds were chemically etched before graphene growth on Pt.…”

“…The Au thin film prevents graphene seed arrays from direct contact with polymers used in the photolithography and transfer process. 21 After transfer to the growth substrate, organic residues on the substrate were removed using O 2 plasma, and then Au protective layers on graphene seeds were chemically etched before graphene growth on Pt. Among various catalytic substrates for the CVD growth of high-quality graphene, Pt substrate was selected in this work because it is chemically stable during O 2 plasma cleaning or chemical etching of the Au layer on the graphene seed.…”

Developing Graphene‐Based Moiré Heterostructures for Twistronics

“…g,h) Reproduced under the terms of the Creative Commons CC‐BY license. [ 66 ] Copyright 2019, The Authors. Published by MDPI.…”

“…This method takes advantage of the different adhesions between the interfaces to selectively pick up the graphene. [ 66 ] First, the single‐crystal MLG was prepared on a Ge (110) wafer, and a gold pattern was then fabricated on the as‐grown MLG. The most important factor was that annealing in H 2 could reduce the adhesion between graphene and the Ge substrate.…”

“…h) The SAED of tBLG with twist angle of 12°. g,h) Reproduced under the terms of the Creative Commons CC-BY license [66]. Copyright 2019, The Authors.…”