Scalable fabrication of graphene nanoribbon quantum dot devices with stable orbital-level spacing

• Published in: Communications materials Vol. 3; no. 1; pp. 103 - 7
• Main Authors: Kato, Toshiaki, Kitada, Takahito, Seo, Mizuki, Okita, Wakana, Sato, Naofumi, Shinozaki, Motoya, Abe, Takaya, Kumasaka, Takeshi, Aizawa, Takumi, Muto, Yui, Kaneko, Toshiro, Otsuka, Tomohiro
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.12.2022; Nature Portfolio
• Subjects: Devices; Diamonds; Graphene; High temperature; Nanoribbons; Nuclear spin; Quantum dots; Qubits (quantum computing); Spin-orbit interactions; Substrates
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-022-00326-3

Abstract Large-scale integration of quantum-dot devices is essential for realizing various quantum devices. Graphene-based quantum dots provide a promising platform for spin qubits because of their low nuclear spin density and weak spin-orbit interaction. However, the integration of graphene-based quantum dots remains a challenge. Here, we demonstrate the scalable fabrication of graphene nanoribbon-based quantum-dot devices using a nickel nanobar technique. Fine structures formed in the middle of the nanoribbons exhibit quantum-dot behavior, and more than 56% of devices fabricated on the same substrate show Coulomb diamond features, indicating that large-scale integration of graphene nanoribbon quantum-dot devices is possible with our method. Cryogenic measurements reveal orbital-level spacings between the ground and excited states that are stable up to high-temperature conditions of ~20 K. We explain this stability in terms of the very fine structures formed in the middle of the nanoribbons and their relatively low effective mass.