Orientation-Dependent Thermoelectric Engineering of Rectangular Nanopores in Bismuth Nanoribbons: Effects on Electronic Conductance, Bandgap, and Seebeck Coefficient

We investigate the influence of rectangular nanopores on the electronic and thermoelectric properties of zigzag bismuth nanoribbons using a tight-binding framework combined with the Green’s function formalism. The study focuses on how the geometry and orientation of nanopores affect the electronic conductance, energy bandgap, and Seebeck coefficient. Our calculations show that introducing nanopores along both the transport and transverse directions strongly modifies the transport behavior of the nanoribbon. Elongating the nanopore along the transport direction induces moderate scattering and weak perturbation of conductance, resulting in a slight reduction in transmission and a small widening of the energy gap. In contrast, widening the pore perpendicular to the transport direction produces a much stronger effect, notably suppressing conductance near the Fermi level and significantly increasing the bandgap. Moreover, the calculated Seebeck coefficient exhibits a remarkable enhancement with increasing pore width, which is attributed to the evolution of the conductance spectrum toward a boxcar-like shape—a feature known to improve thermoelectric performance. These findings demonstrate that nanopore geometry and orientation can be effectively utilized to tailor both the electronic and thermoelectric characteristics of bismuth-based low-dimensional nanostructures for future energy-conversion and nanoelectronic applications.