(2021) Stephan Roche: Emerging properties of amorphous layered membranes (carbon and boron-nitride)

Catalan Institute of Nanoscience Nanotechnology, Campus UAB, Bellaterra, Spain ICREA, Institució Catalana de Recerca i Estudis Avancats, Spain Formidable progress has been recently achieved in the fabrication and characterization of disordered materials with unprecedented properties. In this context, particular forms of disordered graphene (reduced graphene oxides), obtained by chemical exfoliation techniques, have been found suitable to improve the performances of composite materials, with application in energy. Moreover, the recent demonstrated possibility to synthesize wafer-scale two-dimensional amorphous carbon monolayers and boron-nitride, structurally dominated by sp2 hybridization has initiated a new platform of low-dimensional materials to explore as alternative forms of membranes with enhanced chemical reactivity which could serve as coating materials. The excellent physical properties of the mentioned materials derive from the nature and degree of their disorder which, controlled at the fabrication level, represents the key ingredient to tune their physical/chemical properties for specific target applications. In this respect, new fabrication strategies to modify the degree of disorder and a systematic theoretical characterization of the impact of the material structural quality on the ultimate performance is urgent. Here, I will present the results of our theoretical investigation of systematic analysis of the structural and vibrational properties of amorphous carbon and boron nitride monolayers as a function of the structural quality of the material, showing how disorder results in a tunable thermal conductivity and electrical conductivity varying by orders of magnitude. In particular, I will identify how energy is dissipated in this material by a systematic analysis of emerging vibrational modes whose localization increases with the loss of spatial symmetries. Our simulations provide some recipe to design most suitable "amorphous graphene" based on the target applications such as ultrathin heat spreaders, energy harvesters or insulating thermal barriers. The unprecedented properties of amorphous boron nitride will be also discussed in the context of recent discovery of their ultralow dielectric coefficient, which provides an exceptional material for further boosting interconnects technologies in advanced nanoelectronics. ICREA Prof. Stephan Roche is working at the Catalan Institute of Nanosciences and Nanotechnology-ICN2 and BIST. He leads the "Theoretical and Computational Nanoscience" group which focuses on physics of Dirac materials (graphene & topological insulators), 2D materials-based van der Waals heterostructures and amorphous matter. He pioneered the development of linear scaling quantum transport approaches enabling simulations of billion atoms-scale disordered models. He studied Theoretical Physics at ENS and got PhD (1996) at Grenoble University (France); worked in Japan, Spain & Germany; was appointed as assistant Prof. in 2000, CEA Researcher in 2004 and joined ICREA in 2009. He received the Friedrich Wilhelm Bessel prize from the Alexander von Humboldt Foundation (Germany). He is one of the founder of the Graphene Flagship initiative, currently workpackage (spintronics) and Division (fundamental science) leader. TUTORIAL: Review of Polycrystalline Graphene Properties Professor Stephan Roche is also offering a tutorial, "Review on Polycrystalline Graphene Properties", at 14.00 CET, 1 hour before his main talk. Please register HERE.   Stephan Roche: Review of Polycrystalline Graphene Properties YouTube Video Stephan Roche: Emerging properties of amorphous layered membranes (carbon and boron-nitride) YouTube Video