Microstructure and transport modulation in Zn(Al)O-containing Bi2Te2.7Se0.3 films

Abstract

This work uses dual-beam pulsed laser deposition to fabricate Bi2Te2.7Se0.3 (BTS) films containing Zn(Al)O (AZO)-related heterogeneity and to examine how AZO incorporation affects the microstructure and transport behavior of BTS thin films. By varying the substrate temperature from 250 to 450 °C, we obtained films with distinct morphologies and preferred orientations, ranging from polycrystalline/columnar structures to highly c-oriented layered structures. XRD, HRTEM, STEM-EDS, Raman spectroscopy, and temperature-dependent Hall measurements suggest that AZO incorporation is associated with c-axis expansion, local Zn-rich/ZnAl2O4-related heterogeneity, interfacial defects/twins, and modified carrier-scattering behavior. However, AZO addition does not deliver a clear room-temperature power-factor advantage over undoped BTS under the present processing conditions. Raman and thermal-diffusivity measurements qualitatively suggest altered thermal-transport behavior in the AZO-containing films, but direct thermal-conductivity measurements are still required to confirm the magnitude of this effect. These results show that AZO incorporation modifies the structure-transport relationship of BTS films and provide a basis for further optimization of heterointerface-controlled thermoelectric thin films.a.