Rapid Anisotropic Crystallization from Amorphous Bi₂Te₃ Thin Films by Microwave Annealing

K. Nakagawa (Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan)
T. Iwamoto (Department of Applied Physic, School of Engineering, University of Fukui, Fukui 910-8507, Japan)
I P. A. Karya (Department of Applied Physic, School of Engineering, University of Fukui, Fukui 910-8507, Japan)
A. J. Muhammad (Department of Physics, Faculty of Math and Natural Science, University of Halu Oleo, Kendari 93232, Indonesia)
T. Asano (Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan)
S. Mitsudo (Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan)
T. Takizawa (Department of Materials Science, Tokai University, Kanagawa 259-1292, Japan)
M. Takashir (Department of Materials Science, Tokai University, Kanagawa 259-1292, Japan)

International Journal of Acta Material
Vol. 2 No. 2 (2026): February 2026

We investigated the crystallization behavior of amorphous Bi₂Te₃ thin films subjected to microwave annealing using both slow and rapid heating protocols. Films were deposited by RF magnetron sputtering and annealed with 2.45 GHz microwave irradiation. Slow annealing, performed under controlled temperatures below the melting point of Te, yielded randomly oriented polycrystalline films, whereas rapid annealing with high-power short pulses resulted in strongly c-axis-oriented crystallites. X-ray diffraction (XRD) analyses confirmed enhanced crystallinity and increased Lotgering factors under rapid annealing conditions. SEM observations showed minimal grain growth, suggesting that microwave irradiation promotes preferential orientation without significant grain coarsening. These results indicate that microwave annealing provides a unique, rapid, and effective method for directional crystallization of Bi₂Te₃ thin films, which could significantly enhance their thermoelectric performance.