Periodic Interface Engineering in BN-Modified Bi2Te2.7Se0.3 Thin Films for Enhanced Thermoelectric Transport.

Optimizing thermoelectric transport in Bi2Te3-based thin films requires effective modulation of phonon scattering without severely compromising electronic conductivity. Here, we address this challenge using a periodically modulated architecture composed of alternating pristine Bi2Te2.7Se0.3 (BTS) and BN-modified BTS layers. By systematically varying the stacking period while maintaining a constant total thickness, we examine how interface periodicity influences the microstructure and thermoelectric transport properties of the films. Structural analyses reveal nanoscale lamella-like regions near BTS grain surfaces, likely associated with BN-modified growth, along with local lattice perturbations within the layered BTS framework. The periodically stacked architecture introduces internal interface regions, twin-related structures, and point-defect-rich regions that collectively affect carrier transport and phonon-related scattering. Pisarenko's analysis suggests possible modifications in the electronic density of states or energy-dependent carrier scattering in the multilayer films. As a result, the optimized BTS:BN/BTS-3 film exhibits a power factor of ∼36 μW cm-1K-2. These results demonstrate that periodic interface engineering provides a practical route for tuning thermoelectric transport in vdW-layered Bi2Te3-based thin films without relying on stringent epitaxial lattice matching or complex chemical alloying.