2020年4月22日
Graphene Flagship researchers at RWTH Aachen University, Germany and ONERA-CNRS, France, in collaboration with researchers at the Peter Grunberg Institute, Germany, the University of Versailles, France, and Kansas State University, US, have reported a significant step forward in growing monoisotopic hexagonal boron nitride at atmospheric pressure for the production of large and very high-quality crystals.
Hexagonal boron nitride (hBN) is the unsung hero of graphene-based devices. Much progress over the last decade was enabled by the realisation that 'sandwiching' graphene between two hBN crystals can significantly improve the quality and performance of the resulting devices. This finding paved the way to a series of exciting developments, including the discoveries of exotic effects such as magic-angle superconductivity and proof-of-concept demonstrations of sensors with unrivalled sensitivity.
到目前为止，使用最广泛的HBN晶体来自日本Tsukuba的国家材料科学研究所。欧洲杯线上买球这些晶体是在高温（超过1500°C）和极高的压力（大气压超过40,000倍）下生长的。“日本研究人员塔尼古奇（Taniguchi）和渡边对石墨烯研究的开创性贡献是非常宝贵的。”他从德国德国亚当亚兴大学（Rwth Aachen University）的Chraphene旗舰合作伙伴RWTH ACHEN University开始。“他们免费为世界各地的数百个实验室提供超级HBN。没有他们的贡献，我们今天所做的很多事情将是不可能的。”
However, this hBN growth method comes with some limitations. Among them is the small crystal size, which is limited to a few 100 μm, and the complexity of the growth process. This is suitable for fundamental research, but beyond this, a method with better scalability is needed. Now Graphene Flagship researchers tested hBN crystals grown with a new methodology that works at atmospheric pressure, developed by a team of researchers led by James Edgar at Kansas State University, US. This new approach shows great promise for more demanding research and production.
Stampfer说：“当埃德加（Edgar）提出测试他的HBN质量时，我感到非常兴奋。”“他的增长方法可能适合大规模生产”。在大气压下生长HBN的方法确实比以前的替代方案要简单得多，并且可以控制同位素浓度。
"The hBN crystals we received were the largest I have ever seen, and they were all based either on isotopically pure boron-10 or boron-11" says Jens Sonntag, a graduate student at Graphene Flagship Partner RWTH Aachen University. Sonntag tested the quality of the flakes first using confocal Raman spectroscopy. In addition, Graphene Flagship partners in ONERA-CNRS, France, led by Annick Loiseau, carried out advanced luminescence measurements. Both measurements indicated high isotope purity and high crystal quality.
However, the strongest evidence for the high hBN qualitycame from transport measurements performed on devices containing graphene sandwiched between monoisotopic hBN. They showed equivalent performance to a state-of-the-art device based on hBN from Japan, with better performance in some areas.
Stampfer说：“这清楚地表明了这些HBN晶体的极高质量。”“对于整个石墨烯社区来说，这是个好消息，因为它原则上可以大规模生产高质量的HBN，这使我们更接近基于高性能石墨烯电子产品和光电的真实应用程序。此外，控制晶体的同位素浓度的可能性为以前无法实现的实验打开了大门。”
独立的石墨烯是已知的最薄的材料，表现出较大的表面积，因此对其周围环境非常敏感，进而导致其特殊性质的大量退化。但是，有一个明确的策略来避免这些有害影响：将石墨烯封装在两个保护层之间。”
MarGarcía-Hernández，启用材料的工作包负责人欧洲杯足球竞彩
García-Hernández继续说：“当HBN封装石墨烯时，它揭示了其内在特性。这使HBN成为将石墨烯集成到当前技术中的重要材料，并证明了设计新的可扩展合成路线的重要性不仅提供了一条新的，更简单的路径来大规模生产高质量的HBN晶体，而且还可以产生单异位素材料的产生，从而进一步降低了两层封装时石墨烯的降解。”
这是欧盟与美国之间合作的一个很好的例子，我们通过众多的双边研讨会来培养。设计产生高质量HBN晶体的替代方法对于使我们能够利用石墨烯在光电应用中的最终特性至关重要。此外，这项工作将导致基本研究的重大进展。”
Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel
Source:http://graphene-flagship.eu/