## 2 Methods and Approaches
### Atomistic Models of van der Waals Heterostructures  
In the framework of this study, the following new atomic configurations of van der Waals heterostructures were considered: (1) the configuration based on monolayers of borophene and rhenium sulfide; (2) the configuration based on monolayers of borophene and rhenium selenide. The formation of heterostructures was carried out with the following considerations: (1) the combined layers of the heterostructure should have a small discrepancy in the vectors of the crystal lattice and differ in the type of conductivity; (2) the atomic configuration of the formed heterostructure must be energetically stable. It is known that borophene is a conductor regardless of the type of allotropic modification [45]. On the contrary, rhenium sulfide (ReS\({}_{2}\)) and rhenium selenide (ReSe\({}_{2}\)), depending on the type of crystal system, can exhibit either a metallic character of conductivity, both in the case of a hexagonal crystal system in ReSe\({}_{2}\) and a trigonal crystal system in ReS\({}_{2}\), and also a semiconducting character of conductivity in the case of a triclinic crystal system for both ReSe\({}_{2}\) and ReS\({}_{2}\)[46]. In this regard, the unit cells of the ReSe\({}_{2}\) and ReS\({}_{2}\) of 12 atoms with a triclinic crystal system were chosen to construct the heterostructures. They were taken from the Materials Project open-source database [47]. Among the allotropic forms of borophene, we chose borophene with a triangulated configuration. The triangulated borophene has high energy stability and geometric features that allow it to be combined with ReSe\({}_{2}\) and ReS\({}_{2}\) layers. The unit cell of triangulated borophene consists of two atoms and has optimized translation vectors, L\({}_{\rm x}\) = 1.619 A; L\({}_{\rm y}\) = 2.879 A, which is in good agreement with the known data [45]. Since triangulated borophene has a crystalline structure with a rectangular unit cell, for its successful combination with the ReSe\({}_{2}\) and ReS\({}_{2}\) structures, it was necessary to construct rectangular unit cells for them. Such cells, each consisting of 24 atoms, were obtained from the initial unit cells with the triclinic system by the way clearly illustrated in Figure 1. The equilibrium configurations of the obtained unit cells have the following translation vectors: L\({}_{\rm x}\) = 6.411 A; L\({}_{\rm y}\) = 11.359 A for ReS\({}_{2}\), and L\({}_{\rm x}\) = 6.646 A; L\({}_{\rm y}\) = 11.824 A for ReSe\({}_{2}\). The performed calculations of the density of electronic states (DOS) of the triclinic and rectangular unit cells showed that when passing to a rectangular cell, the features of the electronic structure of ReS\({}_{2}\) and ReSe\({}_{2}\), primarily the presence of an energy gap, remain. In order to minimize the lattice mismatch between the combined monolayers of borophene and ReS\({}_{2}\)/ReSe\({}_{2}\), the sizes of the unit cells of each monolayer were increased until the difference in the parameters of the lattice vectors was no more than 2-3%. To build borophene/ReSe\({}_{2}\) and borophene/ReS\({}_{2}\) heterostructures, the initial unit cell of borophene 1 \(\times\) 2 (the number of atoms along the X and Y axes) was increased 16 times to a size commensurate with rectangular supercells ReSe\({}_{2}\) and ReS\({}_{2}\). The final unit cell of borophene 8 \(\times\) 32 was already 32 atoms. When a borophene monolayer was overlaid to a rectangular cell of ReSe\({}_{2}\), the difference between the lengths of the translation vectors of the stacked monolayers was ~2.63% for the translation vector L\({}_{\rm x}\) and ~2.67% for translation vector L\({}_{\rm y}\). When a borophene monolayer was overlaid to a rectangular cell of ReS\({}_{2}\), the difference between the lengths of the translation vectors was even smaller, as follows: ~1% for L\({}_{\rm x}\); ~1.38% for L\({}_{\rm y}\). Figures 2 and 3 show the process of stacking up monolayers during the formation of the borophene/ReS\({}_{2}\) and borophene/ReSe\({}_{2}\) heterostructures.