As modern integrated circuit technology continually approaches the physical limits of Moore's Law, chip fabrication has entered the atomic scale. In this extreme microscopic realm, traditional silicon-based materials and "top-down" micro/nano fabrication processes face severe challenges: the arrangement of every atom dictates device performance. Finding new semiconductor materials capable of atomic-level precision has become key to sustaining computing power growth.
To break through this bottleneck, tailoring graphene into quasi-one-dimensional "graphene nanoribbons" (GNRs) has emerged as a highly promising solution. However, conventional "top-down" methods struggle to achieve atomic-scale precision, often resulting in rough edges and defects that severely scatter electrons. Addressing this challenge, scientists have pioneered an alternative "bottom-up" chemical synthesis strategy. This approach, akin to "building blocks" in the microscopic world, uses small molecular precursors for atomically precise assembly, successfully achieving ultimate control over nanoribbon width and edge structure. This atomic-level manufacturing precision not only precisely opens the bandgap of graphene but also unlocks quantum properties like spin-polarized edge states unattainable in traditional materials, signifying that chip material fabrication capability has truly reached the atomic limit.
Nature Reviews Materialsrecently published a review article titled "Bottom-up synthesized graphene nanoribbons for nanoelectronics." The article was co-authored by researchers including Prof. ZHANG Jian from the National Center for Nanoscience and Technology, China (NCNST), Prof. Roman Fasel, Prof. Michel Calame and Dr. Gabriela Borin Barin from the Swiss Federal Laboratories for Materials Science and Technology (Empa), and Prof. Mickael Perrin from ETH Zurich. The article systematically reviews the latest progress in integrating atomically precise GNRs from chemical synthesis to high-performance electronic devices, charting a clear roadmap for next-generation carbon-based nanoelectronics and quantum technologies.
From Synthesis Challenges to Device Integration
Despite breakthroughs in synthesis techniques, integrating these molecular ribbons, only 1–2 nanometers wide, into functional electronic devices remains a significant challenge. The article details core elements in the device integration process, including contact geometry, gate architecture, and channel design. To achieve high-performance field-effect transistors (FETs), researchers have developed various contact strategies, evolving from metal contacts to graphene or carbon nanotube contacts to optimize charge transport. Notably, recent breakthroughs in direct growth of ultra-long GNRs on insulating hexagonal boron nitride (h-BN) substrates via chemical vapor deposition (CVD) enable device fabrication without transfer steps, avoiding contamination and achieving extremely high carrier mobility, demonstrating great potential for low-power logic circuits.
A Unique Platform for Next-Generation Quantum Technologies
Beyond classical transistor applications, the review emphasizes that atomically precise GNRs are not only strong candidates for post-Moore electronics but also an ideal platform for next-generation quantum technologies. Compared to traditional semiconductor quantum dots or carbon nanotubes, GNRs exhibit unique "chemical programmability"—the position, size, and coupling strength of quantum dots can be precisely defined through underlying chemical synthesis. This atomic-level control is difficult to achieve with other materials. Benefiting from extremely weak spin-orbit coupling and hyperfine interactions, GNRs endow electron spins with exceptionally long coherence times, making them ideal carriers for building spin qubits. The review notes that by integrating double or multiple quantum dot structures within nanoribbons, precise manipulation of charge and spin states can be achieved, a necessary step toward logical quantum gates.
Potential for High-Temperature Spintronics and Energy Applications
More exciting is the potential of GNRs in high-temperature spintronics. The article highlights chemically designed "spin chain" structures. By precisely controlling the distance between spin centers to just a few nanometers, the magnetic exchange coupling energy within GNRs can exceed 100 meV, far above room-temperature thermal energy. This means spin-based devices using GNRs could potentially operate at room temperature, paving a new path for non-cryogenic quantum computing.
Beyond computing, GNRs also show remarkable prospects in energy and fundamental physics frontiers. Benefiting from their large charging energies up to 500 meV and sharp energy levels, GNRs can serve as efficient quantum heat engines, performing energy conversion near thermodynamic limits. In topological physics, the review explores topological boundary states realized via GNR heterojunctions. These protected quantum states are inherently immune to disorder and scattering, providing a solid physical foundation for fault-tolerant quantum computing. Furthermore, when GNRs are embedded in h-BN lattices, slight lattice mismatch forms one-dimensional moiré superlattices, offering an unprecedented experimental platform for exploring strongly correlated quantum phases like unconventional superconductivity or magnetism.
Atomically precise GNRs provide a unique opportunity to perfectly combine "the precision of chemical synthesis" with "the complexity of quantum devices". With the maturation of clean transfer techniques and surface passivation processes, GNRs are poised to transform from laboratory micro-marvels into core engines driving future quantum computers, ultra-sensitive sensors, and high-efficiency energy converters.
Scheme Quantum Device with Atomically Precise Graphene Nanoribbons (Image by ZHANG Jian et al)
Contact: ZHANG Jian
National Center for Nanoscience and Technology (NCNST)
E-mail: zhangjian@nanoctr.cn
