Publication date: 11th July 2022
Van der Waals heterostructures (vdWHs) provide the possibility of engineering new materials with emergent functionalities that are not accessible in another way. These heterostructures are formed by assembling layers of different materials used as building blocks. Beyond inorganic 2D crystals, layered molecular materials remain still rather unexplored, with only few examples regarding their isolation as atomically thin layers. Here, the family of van der Waals heterostructures is enlarged by introducing a molecular building block able to produce strain: the so-called spin-crossover (SCO). In these metal–organic materials, a spin transition can be induced by applying external stimuli like light, temperature, pressure, or an electric field. In particular, smart vdWHs are prepared in which the electronic and optical properties of the 2D material (graphene and WSe2) are clearly switched by the strain concomitant to the spin transition. These molecular/inorganic vdWHs represent the deterministic incorporation of bistable molecular layers with other 2D crystals of interest in the emergent fields of straintronics and band engineering in low-dimensional materials.
The authors acknowledge the financial support from the European Union (ERC AdG Mol-2D 788222, FET-Open COSMICS 766726), the Spanish MICINN (2D-HETEROS PID2020-117152RB-100, SUPERSCO PID2020-117264GB-100, co-financed by FEDER, and Excellence Unit “María de Maeztu” CEX2019-000919-M), and the Generalitat Valenciana (PROMETEO Program and PO FEDER Program, IDIFEDER/2018/061). C.B.-C. thanks the Generalitat Valenciana for a Ph.D fellowship. The authors thank Safiya Ouazza for her help regarding the WSe2-based vdWHs and Ángel López-Muñoz for his constant technical support and helpful discussions.