Anisotropic Analysis of Nanocrystalline Bismuth Telluride Thin Films Treated by Homogeneous Electron Beam Irradiation

Abstract

The in-plane and cross-plane transport properties of nanocrystalline bismuth telluride (Bi 2 Te 3 ) thin lms were evaluated to analyze their anisotropic behavior. Bi 2 Te 3 thin lms were prepared via radio frequency (RF) magnetron sputtering, followed by a subsequent treatment of thermal annealing and homogeneous electron beam (EB) irradiation at various EB doses. The crystallographic properties of the thin lms were determined by X-ray diffraction (XRD) analysis. It was determined that the crystal orientation (Lotgering factor; F value) of Bi 2 Te 3 thin lms can be controlled by homogeneous EB irradiation treatments, without resulting in crystal growth. The electrical conductivity and Seebeck coefcient were measured in the in-plane direction of the lms, and the thermal conductivity was measured in the cross-plane direction using the 3ω method. The anisotropic analysis was performed by combining the F value of the thin lms with a simple model based on the transport properties of the basal and lateral planes of single-and poly-crystal Bi 2 Te 3 . The electrical and thermal conductivities of the in-plane and cross-plane directions of the EB-irradiated thin lms clearly differed; however, there was no signi cant difference between the Seebeck coef cient values of the two planes. Finally, we determined that the gure of merit, ZT, was enhanced by the homogeneous EB irradiation treatment, and the inplane ZT value was 25% greater than that of the cross-plane direction.

Thermal annealing effect on structural and thermoelectric properties of hexagonal Bi2Te3 nanoplate thin films by drop-casting technique

“…Because of this crystal structure, the lattice constant in the c-axis is approximately seven times larger than that in the a,b-axis. As a result, Bi 2 Te 3 exhibits a remarkable anisotropic behavior [11][12][13] and its electrical conductivity along the a,b-axis direction is approximately three times larger than that along the c-axis direction. 14) A nanoplate is an ideal shape for the Bi 2 Te 3 to exhibit its remarkable anisotropic behavior.…”

Combination of Electrodeposition and Transfer Processes for Flexible Thin-Film Thermoelectric Generators

“…Therefore, we considered that the electrodeposited Bi 2 Te 3 and Sb 2 Te 3 thin films in this study would show similar trends. To further increase thermoelectric properties in the future, we plan to carry out not only additional treatments such as thermal annealing [42][43][44] but also investigate the effects of thermal annealing, i.e., the diffusion between the thermoelectric thin films and the stainless-steel substrate, and the cause of micro-cracks in the films during the transfer of thermoelectric thin films to the flexible sheets. After fabricating the flexible thin-film generators, we calculated the electrical resistance of the generators based on the thermoelectric properties of the n-and p-type thin films.…”

Experimental and Computational Analyses of Temperature Distributions in Slope-Type Thin-Film Thermoelectric Generators at Different Slope Angles and Evaluation of Their Thermoelectric Performance

“…In thermoelectric materials, bismuth-telluride-based alloys are the most favorable materials for IoT applications because they exhibit the highest thermoelectric performance near 300 K [24][25][26]. Therefore, although bismuth-telluride-based alloys were developed in the 1950s [27,28], they are still being actively researched [29][30][31][32].…”