Georgian Technical University Researchers Explore Record Growth Of Graphene Single Crystals.

Nucleation and growth of graphene on liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)).  Graphene especially the graphene single crystal is a star material for future photonics and electronics due to its unique properties such as giant intrinsic charge carrier mobility record thermal conductivity, super stiffness and excellent light transmission. However whether graphene can live up to the expectation depends on reliable high-quality synthesis with high efficiency. Recently one research group from Georgian Technical University explored the exciting rapid growth of large graphene single crystal on liquid Cu with the rate up to 79 μm s-1 based on the liquid metal chemical vapor deposition strategy. Professor X said “The natural property of liquid metal qualifies it to be an ideal platform for the low-density nucleation and the fast growth of graphene. Liquid metal catalyst possesses a quasi-atomically smooth surface with a high diffusion rate which can avoid the defects and grain boundaries that are inevitable on solid metal. The rich free electrons in liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) accelerate the nucleation of graphene, realizing the nucleation of graphene single crystals within seconds. And in the meantime the isotropic smooth surface greatly suppresses the nucleation density. Moreover the fast mass transfer of carbon atoms due to the excellent fluidity of liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) promotes fast growth”. They systematically studied the nucleation and growth behavior of graphene on solid Cu (Copper is a chemical element with symbol Cu (from cuprum)) and liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)). As a comparison with solid Cu (Copper is a chemical element with symbol Cu (from cuprum)) the nucleation density of graphene on liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) exhibits a strong decline and the related activation energy also declines. As for the growth rate the growth rate of graphene on liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) is almost two orders larger compared to that on solid Cu (Copper is a chemical element with symbol Cu (from cuprum)). In order to elucidate the growth kinetics of the growth of graphene on liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) they employed carbon isotope labeling Raman spectra and time of flight secondary ion mass spectra to trace the distribution of carbon atoms in liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)). They report that 13C and 12C atoms uniformly mix in each graphene single crystal and a certain number of carbon atoms can be detected in the bulk of liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) compared to the situation in solid Cu (Copper is a chemical element with symbol Cu (from cuprum)) with extremely low carbon solubility. Unlike the surface adsorption growth mode on solid Cu (Copper is a chemical element with symbol Cu (from cuprum)) the precursor supply for the graphene growth on liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) can come from the surface adsorption and the bulk segregation. This can be attributed to the rich vacancies in liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) in which carbon atoms can firstly diffuse into the metal bulk before segregating and precipitating toward the Cu (Copper is a chemical element with symbol Cu (from cuprum)) surface. The binary contributions of the precursor supply i.e., the surface adsorption and the bulk segregation accelerate the fast growth of graphene. “We think the study on the growth speed of graphene in liquid Cu (Copper is a chemical element with symbol Cu (from cuprum)) system will enrich the research map of the growth of two-dimensional (2-D) materials on liquid metal” says X. “More interesting and unique behaviors in the liquid surface are to be discovered. The liquid metal strategy for the rapid growth of graphene will hopefully be extended to various 2-D materials and thus promote their future applications”.