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- ItemHigh-Quality Graphene Using Boudouard Reaction(Weinheim : Wiley-VCH, 2022) Grebenko, Artem K.; Krasnikov, Dmitry V.; Bubis, Anton V.; Stolyarov, Vasily S.; Vyalikh, Denis V.; Makarova, Anna A.; Fedorov, Alexander; Aitkulova, Aisuluu; Alekseeva, Alena A.; Gilshtein, Evgeniia; Bedran, Zakhar; Shmakov, Alexander N.; Alyabyeva, Liudmila; Mozhchil, Rais N.; Ionov, Andrey M.; Gorshunov, Boris P.; Laasonen, Kari; Podzorov, Vitaly; Nasibulin, Albert G.Following the game-changing high-pressure CO (HiPco) process that established the first facile route toward large-scale production of single-walled carbon nanotubes, CO synthesis of cm-sized graphene crystals of ultra-high purity grown during tens of minutes is proposed. The Boudouard reaction serves for the first time to produce individual monolayer structures on the surface of a metal catalyst, thereby providing a chemical vapor deposition technique free from molecular and atomic hydrogen as well as vacuum conditions. This approach facilitates inhibition of the graphene nucleation from the CO/CO2 mixture and maintains a high growth rate of graphene seeds reaching large-scale monocrystals. Unique features of the Boudouard reaction coupled with CO-driven catalyst engineering ensure not only suppression of the second layer growth but also provide a simple and reliable technique for surface cleaning. Aside from being a novel carbon source, carbon monoxide ensures peculiar modification of catalyst and in general opens avenues for breakthrough graphene-catalyst composite production.
- ItemHigh-performance electronics and optoelectronics of monolayer tungsten diselenide full film from pre-seeding strategy(Weinheim : Wiley, 2021) Zhang, Shu; Pang, Jinbo; Cheng, Qilin; Yang, Feng; Chen, Yu; Liu, Yu; Li, Yufen; Gemming, Thomas; Liu, Xiaoyan; Ibarlucea, Bergoi; Yang, Jiali; Liu, Hong; Zhou, Weijia; Cuniberti, Gianaurelio; Rümmeli, Mark H.Tungsten diselenide (WSe2) possesses extraordinary electronic properties for applications in electronics, optoelectronics, and emerging exciton physics. The synthesis of monolayer WSe2 film is of topmost for device arrays and integrated circuits. The monolayer WSe2 film has yet been reported by thermal chemical vapor deposition (CVD) approach, and the nucleation mechanism remains unclear. Here, we report a pre-seeding strategy for finely regulating the nuclei density at an early stage and achieving a fully covered film after chemical vapor deposition growth. The underlying mechanism is heterogeneous nucleation from the pre-seeding tungsten oxide nanoparticles. At first, we optimized the precursor concentration for pre-seeding. Besides, we confirmed the superiority of the pre-seeding method, compared with three types of substrate pretreatments, including nontreatment, sonication in an organic solvent, and oxygen plasma. Eventually, the high-quality synthetic WSe2 monolayer film exhibits excellent device performance in field-effect transistors and photodetectors. We extracted thermodynamic activation energy from the nucleation and growth data. Our results may shed light on the wafer-scale production of homogeneous monolayer films of WSe2, other 2D materials, and their van der Waals heterostructures.
- ItemSubstrate Developments for the Chemical Vapor Deposition Synthesis of Graphene(Weinheim : Wiley-VCH Verlag, 2020) Shi, Q.; Tokarska, K.; Ta, H.Q.; Yang, X.; Liu, Y.; Ullah, S.; Liu, L.; Trzebicka, B.; Bachmatiuk, A.; Sun, J.; Fu, L.; Liu, Z.; Rümmeli, M.H.Since the isolation of graphene and numerous demonstrations of its unique properties, the expectations for this material to be implemented in many future commercial applications have been enormous. However, to date, challenges still remain. One of the key challenges is the fabrication of graphene in a manner that satisfies processing requirements. While transfer of graphene can be used, this tends to damage or contaminate it, which degrades its performance. Hence, there is an important drive to grow graphene directly over a number of technologically important materials, viz., different substrate materials, so as to avoid the need for transfer. One of the more successful approaches to synthesis graphene is chemical vapor deposition (CVD), which is well established. Historically, transition metal substrates are used due to their catalytic properties. However, in recent years this has developed to include many nonmetal substrate systems. Moreover, both solid and molten substrate forms have also been demonstrated. In addition, the current trend to progress flexible devices has spurred interest in graphene growth directly over flexible materials surfaces. All these aspects are presented in this review which presents the developments in available substrates for graphene fabrication by CVD, with a focus primarily on large area graphene.