Electrodeposition and Thermoelectric Characterization of (00L)-Oriented Bi₂Te₃Thin Films on Silicon with Seed Layer

Abstract

Bi 2 Te 3 thin films were electrodeposited on silicon substrate with a epitaxial seed layer from acidic aqueous solutions at room temperature. The seed layer optimized the charge transfer in the electrodeposition process and reduced the lattice mismatch between the thin film and the substrate, leading to the Bi 2 Te 3 thin films with uniform structure and highly crystallographically texture. By changing the substrate from doped to intrinsic silicon, we obtained the Bi 2 Te 3 thin films with (00L) preferential orientation which is different from previously reported (015) or (110)-oriented thin films prepared by ECD. The (00L)-oriented thin film showed a more compact structure with lower roughness and an improved thermoelectric performance. The electrical conductivity increased by about 72% compared with the (110)-oriented thin film in our system. Simultaneously, the Seebeck coefficient was comparable, indicating the improvement of power factors by ∼45%. We also altered the thickness of the seed layer from 40 nm to 20 nm and found that both the electrical conductivity and Seebeck coefficient decreased due to the insufficient charge transfer in the electrodeposition process.

Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response

“…Using this technique, a Seebeck coefficient of S = −121(±6) μV K –1 was consistently measured on a range of different contact pads. This value is consistent with previous n-type Bi 2 Te 3 materials reported in the literature. − …”

Comprehensive Review on Thermoelectric Electrodeposits: Enhancing Thermoelectric Performance Through Nanoengineering

“…Moreover, the Seebeck coefficient can be improved from 28 to 112.3 µV/K and the power factor can be improved from 2.57 to 443 µW/(K 2 •m) by post-annealing process . Cao et al (2013) fabricated thin Bi 2 Te 3 films by electrodeposition in the solution with 10 mM HTeO 2 + , 8 mM Bi 3+ and 1 M HNO 3 at room temperature. The substrates used during the deposition had an epitaxial seed layer, which would help to reduce the lattice mismatch between Bi 2 Te 3 and Silicon.…”

“…Additionally, the electrical conductivity and Seebeck coefficient was suppressed by reducing the seed layer thickness from 40 to 20 nm, which can be attributed to the insufficient charge transfer during electrodeposition (Cao et al, 2013). Wu et al (2013) investigated the effect of chloride on the electrodeposition of Bi 2 Te 3 films in the solution containing TeCl 4 , Bi(NO 3 ) 3 •5H 2 O and ethylene glycol.…”

Electrodeposition of p-Type Sb2Te3 Films and Micro-Pillar Arrays in a Multi-Channel Glass Template

“…Many advances in the fabrication of microscopic TE devices combined with microelectromechanical systems processing have been achieved in recent years. However, there are still some important problems that have limited the performance and application of TE micro-devices; for instance, the complex mic-fabrication process, the quality of TE materials including thin films and microarrays, the aspect ratio of microarrays, and contact resistance [3,9,10,12,14,18,19,20,21,22,23,24,25,26]. …”

“…Bismuth telluride (Bi 2 Te 3 )-based alloys are the best n-type TE materials near room temperature and the corresponding films and microarrays have been studied extensively in TE micro-devices. The electrodeposition of Bi 2 Te 3 films has been well reported because electrochemical deposition has many advantages including comparably facile control over process parameters, low cost, low temperature, and relatively simple equipment requirements [4,9,14,17,22,25,27,28,29,30]. Additionally, electrodeposited materials can be integrated into micro-devices.…”