Over the last years, two-dimensional (2D) materials (e.g. graphene, hexagonal boron-nitride MoS2) have attracted considerable interest due to that they offer a new broad playground to explore and develop nanoscale devices with tailored electrical, optical and thermal properties. Recently, many prototypes have been proposed for thermal devices (diodes, transistors, and logic gates) based on graphene. Most of these investigations have focused on how to control the heat flux in order to display heat rectification. From the point of view of simulating heat transport, it has been found that thermal rectification in nanostructured systems sensitively depends on several parameters such as heat bath features, device geometry, and on the interface properties between different materials inside the device. A common conclusion for these studies is that the simplest mechanism to induce thermal rectification in confined nanoscale systems is to introduce structural asymmetries.

Here, we provide insights into the design and understanding of thermal rectifiers based on asymmetric nanostructures composed of MoS2 and hBN-C monolayers. Non-equilibrium molecular dynamics (NEMD) simulations are used to study the influence of geometrical shapes on the thermal rectification. Our results point out that asymmetric nanoribbons can display considerable thermal rectification. Moreover, this rectifier effect increases with the asymmetry degree of the device but, as expected, it weakens with increasing linear dimensions. We have also found that lateral confinement of the vibrational modes is a mechanism of thermal rectification in those nanoribbons. Hence, our results can help to optimize the composition of nanostructured materials in order to design novel thermal devices with a high rectification degree. We remark that nanostructures as those investigated here may be already accessible to state of the art experimental approaches.