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Bubble-Free Transfer Technique for High-Quality Graphene/Hexagonal Boron Nitride van der Waals Heterostructures

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posted on 06.02.2020, 16:34 by Takuya Iwasaki, Kosuke Endo, Eiichiro Watanabe, Daiju Tsuya, Yoshifumi Morita, Shu Nakaharai, Yutaka Noguchi, Yutaka Wakayama, Kenji Watanabe, Takashi Taniguchi, Satoshi Moriyama
Bubbles at the interface of two-dimensional layered materials in van der Waals heterostructures cause deterioration in the quality of materials, thereby limiting the size and design of devices. In this paper, we report a simple all-dry transfer technique, with which the bubble formation can be avoided. As a key factor in the technique, a contact angle between a picked-up flake on a viscoelastic polymer stamp and another flake on a substrate was introduced by protrusion at the stamp surface. Using this technique, we demonstrated the fabrication of high-quality devices on the basis of graphene/hexagonal boron nitride heterostructures with a large bubble-free region. Additionally, the technique can be used to remove unnecessary flakes on a substrate under an optical microscopic scale. Most importantly, it improves the yield and throughput for the fabrication process of high-quality van der Waals heterostructure-based devices.