Significant contact resistance between deposited metal and 2D semiconducting channels severely deteriorates device performance due to the Fermi level pinning at the interface 20, which makes it difficult to utilize the 2D semiconductors for practical applications required by the industry. To improve the device performance of 2D semiconductors, contact resistance and carrier scattering should be reduced. Despite the unique properties of ReS 2 and ReSe 2, there have been only limited studies on them, which reported preliminary results of transistors and photodetectors based on ReS 2 and ReSe 2 with conventional device geometry 14, 15, 16, 17, 18, 19. However, ReS 2 and ReSe 2 exhibit direct band structure at all thickness because of the distorted 1 T’ structure and weak interlayer coupling 13. Typically, few-layer TMDs outperform monolayer in terms of carrier mobility, while the band structure of TMDs transforms from direct to indirect band structure as the thickness changes from monolayer to few-layers, which limits their use for optoelectronic applications 12. As emerging 2D materials, rhenium-based TMDs, such as ReS 2 or ReSe 2, have exhibited promising properties. In this regard, “all-2D” devices comprising only 2D materials, i.e., van der Waals heterostructure (vdW) devices, have been demonstrated 8, 9, 10, 11. It has been anticipated that a scale-down limit can be overcome by 2D semiconductors for higher integration of electronic devices. Among them, transition metal dichalcogenides (TMDs) have been actively studied as channel materials because of absence of short-channel effect 6, 7. Ultrathin two-dimensional (2D) semiconducting materials are useful for a number of electronic applications because of their unique properties originating from their atomically thin nature 1, 2, 3, 4, 5. The vdW heterostructure NAND gate comprising a single transistor paves a novel way to realize “all-2D” circuitry for flexible and transparent electronic applications. Highly sensitive electrostatic doping of ReS 2 enables fabrication of gate-tunable NAND logic gates, which cannot be achieved in bulk semiconductor materials because of the absence of gate tunability. In this study we report high-performance van der Waals heterostructure (vdW) ReS 2 transistors with graphene electrodes on atomically flat hBN, and demonstrate a NAND gate comprising a single ReS 2 transistor with split gates. If logic devices can be realized in a single channel, it would be advantageous for higher integration and functionality. Even though a number of 2D-materials-based logic devices have been demonstrated to date, most of them are a combination of more than two unit devices. Two-dimensional (2D) semiconductors, such as transition metal dichalcogenides (TMDs) and black phosphorus, are the most promising channel materials for future electronics because of their unique electrical properties.
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