Researchers at the University of Bologna have introduced and considered a single layer of brucite Mg(OH)2, a 2D material that can be easily produced by exfoliation (like graphene from graphite), for the creation of van der Waals composites (known as heterostructures, or heterojunctions), where two monolayers of different materials are stacked and held together by dispersive interactions.
First principles simulations showed that brucite/graphene composites can modify the electronic properties (position of the Dirac cone with respect to the Fermi level and band gap) according to the crystallographic stacking and the presence of point defects. This could be meaningful for various applications, such as electronics.
Brucite is a naturally occurring mineral that is identified as a promising partner for graphene due to its unique characteristics. The study underscores the need for reliable 2D materials offering both hydrophobicity and surface flatness to enhance carrier mobility in graphene-based heterostructures. Brucite, with its inherent properties, stands out as an excellent candidate for this role in the development of nanoelectronic devices.
The team performed a detailed ab initio Density Functional Theory investigation at the PBE-D2 level and using atom-centred atomic orbitals to characterize the interaction between a single brucite layer and graphene, and its effects on the structure and electronic properties. The crystallographic relationships between the two monolayers were considered by realizing several heterojunctions to properly account for inequivalent stacking and to investigate how the crystal-chemistry and point defects/substitutions could affect the position of the electronic bands, their occupation, and the emergence of possible band gaps.
The brucite-graphene composites can alter the electronic properties of graphene, depending on the crystallographic stacking and the presence of point defects. These changes include the shift in the position of the Dirac cone relative to the Fermi level and the band gap. This suggests that heterostructures, held together by weak van der Waals interactions, can be engineered to fine-tune the properties of these composite materials.
The present work represents a step forward in understanding and finding new ways to design two-dimensional materials with tailored electronic and physical properties.