First principles design and band engineering of type-II As₂C₃/Sc₂CF₂ van der Waals heterostructure

In this work, we systematically investigate the structural, electronic, mechanical, thermal, and optical properties of a two-dimensional (2D) As₂C₃/Sc₂CF₂ van der Waals (vdW) heterostructure using first-principles calculations. All stacking configurations preserve the semiconducting nature of their constituent monolayers with indirect bandgaps and form a type-II band alignment, favorable for efficient charge separation. The As₂C₃/Sc₂CF₂ heterostructure exhibits excellent mechanical robustness and thermal stability. Optical absorption spectra reveal a significant enhancement across a broad spectral range, with the absorption coefficient reaching up to 3.5 × 10⁵ cm^-1. Furthermore, the electronic properties and contact behavior of the heterostructure can be effectively tuned by applying an external electric field. Notably, a semiconductor-to-metal transition is induced under negative electric field, while a reversible switching between type-II and type-I band alignments is achieved under the positive direction. These results underscore the potential of the As₂C₃/Sc₂CF₂ heterostructure as a versatile candidate for future nanoelectronic, optoelectronic, and field-effect device applications.