Researchers from the University of Manchester and the University of Sheffield have discovered the properties of graphene can be changed by stacking layers like a tower of Lego.
The research, published in Nature, found that when atomically thin – effectively two-dimensional – layers are stacked on top of each other, the resultant forces cause the properties of the material to change, creating a new material with “novel hybrid properties”. The researchers further discovered that the properties of the secondary material can be affected through twisting the different layers in the stack.
The layers are attached to each other through a weak Van Der Waals reaction, rather than via any physical meeting or chemical interaction, forming a “heterostructure” – a process first implemented in the 1960s, layering gallium arsenide to build miniature lasers – which forms as a moiré superlattice. Professor Vladimir Falko, Director of the National Graphene Institute, said: “By controlling the hybridisation of electron’s states in heterostructures and also using moiré superlattice effects, which are generic for heterostructures of atomically thin films, we acquire a new handle for tailoring optical properties of materials.”
The researchers highlighted the potential of the newly discovered “van der Waals heterostructures” for the creation of designer materials or unique, novel devices through different stacking permutations of the two-dimensional layers. Theoretically this could lead to further developments in optoelectronic device functionality or the exploration of unusual material properties.
Professor Alexander Tartakovskii, Professor of Solid State Physics at the University of Sheffield, said: “The more complex picture of interaction between atomically thin materials within van der Waals heterostructures emerges. This is exciting, as it gives the opportunity to access an even broader range of material properties such as unusual and twist-tunable electrical conductivity and optical response, magnetism etc. This could and will be employed as new degrees of freedom when designing new 2D-based devices.”