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

• Published in: Communications materials 2022-12, Vol.3 (1), p.103-7, Article 103
• 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: Article
• Language: English
• Subjects: 639/925/918/1052; 639/925/918/1055; Chemistry and Materials Science; Devices; Diamonds; Graphene; High temperature; Materials Science; Nanoribbons; Nuclear spin; Quantum dots; Qubits (quantum computing); Spin-orbit interactions; Substrates
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-022-00326-3

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. Graphene nanoribbons can be used as quantum dot devices, but scalable fabrication methods are needed. Here, a nanobar technique is used to synthesize graphene nanoribbon-based quantum dot devices with a 56 % yield and stable orbital level splitting up to 20 K.