Moiré-Induced Transport in CVD-Based Small-Angle Twisted Bilayer Graphene

Abstract

To realize the applicative potential of 2D twistronic devices, scalable synthesis and assembly techniques need to meet stringent requirements in terms of interface cleanness and twist-angle homogeneity. Here, we show that small-angle twisted bilayer graphene assembled from separated CVD-grown graphene single-crystals can ensure high-quality transport properties, determined by a device-scale-uniform moiré potential. Via low-temperature dual-gated magnetotransport, we demonstrate the hallmarks of a 2.4°-twisted superlattice, including tunable regimes of interlayer coupling, reduced Fermi velocity, large interlayer capacitance, and density-independent Brown-Zak oscillations. The observation of these moiré-induced electrical transport features establishes CVD-based twisted bilayer graphene as an alternative to “tear-and-stack” exfoliated flakes for fundamental studies, while serving as a proof-of-concept for future large-scale assembly.

Growth and applications of two-dimensional single crystals

“…The degree of engineering resulting from the twistronic approach [132] is unprecedented and holds great potential for fields such as quantum technologies [133]. Thus, efforts toward up-scaling of TBG are of high current interest [134]. Magic angle conditions for multilayers have been recently identified [135], in conjunction with unconventional superconducting phases [136][137][138][139].…”

“…They tuned the twist angles of TBG by predesigning the rotation angle of the two single-crystal Cu(111) foils, a centimeterscale Cu/TBG/Cu sandwich structure can be formed by precisely controlling the temperature and the TBG can be isolated by a custom-developed equipotential surface etching method [151]. Despite these promising progresses, artificial stacking mediated by hBN [158] is still to be considered the method-of-choice to access the small-angle limit of TBG, also in the case of samples based on CVD-grown graphene singlecrystals [134].…”

Moiré Synergy: An Emerging Playground by Coupled Moirés

“…But these methods are demanding in intricate workmanship and not scalable for industrial purposes. Ideally, the mass production of moiré materials by chemical vapor deposition (CVD) synthesis is cost-effective and promising for high-quality heterostructures of atomic-level clean and uniform interfaces. , Unfortunately, the traditional CVD requires a high temperature of 550–1000 °C for the reliable growth of crystalline 2D materials, which hinders the sequential growth of component layers of moiré heterostructures due to the thermally induced degradation. Therefore, the low-temperature synthetic strategy for high-crystallinity large-scale multimoiré heterostructures can be one of prospective directions.…”