Stoichiometric Effect of Sb₂Te₃ Thin Film on Thermoelectric Property

Abstract

Properly selecting electrode materials for antimony telluride (Sb 2 Te 3 ) thermoelectric (TE) thin film enhances the power factor. This study analyzed the compositional variation and measured the TE properties of pristine antimony telluride (Sb 2 Te 3 ), Ni/Sb 2 Te 3 / Ni, and Cu/Sb 2 Te 3 /Cu thin films that were aged to simulate real applications. The rapid diffusion of Cu in the Cu/Sb 2 Te 3 /Cu film resulted in the massive growth of the CuTe intermetallic compound (IMC), which led to Te deficiency. Te deficiency causes the formation of antisite Sb Te ′ and reduces the power factor. Antisite Te Sb• increases the power factor because the growth of Sb 2 O 3 on the pristine Sb 2 Te 3 and Ni/Sb 2 Te 3 /Ni films, in which almost no Ni diffusion occurs, results in Sb deficiency. The formation of oxides and IMCs alters the stoichiometry of the films. The formation of the NiTe reaction layer at the interface becomes a self-barrier that inhibits Ni diffusion to the Sb 2 Te 3 film. Herein, a defect reaction is proposed to explain the effects of such changes on the TE properties and the relationship between the stoichiometry of the films and the concentrations of the antisites.

Mitigation of Power Factor Degradation in Bi2Te3 Thin Films

“…Also, the antisite defects of the thermoelectric materials are responsible for their thermoelectric properties. Sun et al proposed a defect reaction model that explains the important role of Sb 2 O 3 in the Sb 2 Te 3 system, which reduces the amount of Sb and increases the excess Te to form the Te Sb · antisite defects . Furthermore, the electronegativity of Bi (2.02) and Te (2.1) is similar.…”

“…Our previous study showed that the thermoelectric properties worsened after long-term aging. The decreased thermoelectric performance may be due to grain coarsening and the annihilation of crystal defects after the aging process. ,, Although the PF of the Cu_30 sample decreased after aging, the degradation was much less than that of the pristine Bi 2 Te 3 after aging for 30 days.…”

“…Sun et al proposed a defect reaction model that explains the important role of Sb 2 O 3 in the Sb 2 Te 3 system, which reduces the amount of Sb and increases the excess Te to form the Te Sb • antisite defects. 33 Furthermore, the electronegativity of Bi (2.02) and Te (2.1) is similar. Therefore, the occupation of Bi atoms for the Te-site was intrinsically exhibited in single-crystal or large-grain Bi 2 Te 3 .…”

Electrodeposited CuSbTe thin films with enhanced thermoelectric performance

“…This suggests that the diffusion of Cu into the Sb lattice site along the c-axis results in the creation of antisite defects by producing more Sb 2 O 3 up to that concentration. 40 Beyond 0.4 mM, the intensity of the Sb-O vibrations decreases as Cu-rich phase formation takes place in the deposited lms. These results are consistent with XRD results as discussed earlier.…”

“…On the other hand, the rapid diffusion of Cu into SbTe and the formation of Sb 2 O 3 may have a considerable effect on the Seebeck coefficient and power factor. 40 The surface Sb 2 O 3 limits the formation of Sb Te antisite defects, and more Cu diffusion leads to the Te sublimation by forming CuSbTe and creates excess V Te , which contributes two electron carriers. Thereby, all the samples behave as n-type, and show a high negative Seebeck coefficient.…”