Enhanced thermoelectric efficiency in topological insulator Bi₂Te₃ nanoplates via atomic layer deposition-based surface passivation

Journal Article · 22 August 2018 · Applied Physics Letters

DOI: https://doi.org/10.1063/1.5030674 · OSTI ID:1510945

Chen, Jihan ^[1]; Kim, Jaehyun  ^[2]; Poudel, Nirakar ^[3]; Hou, Bingya ^[3]; Shen, Lang  ^[4]; Shi, Haotian ^[5]; Shi, Li  ^[2]; Cronin, Stephen  ^[6]

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1. Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering; n/a
2. Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering. Texas Materials Inst.
3. Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering
4. Univ. of Southern California, Los Angeles, CA (United States). Mork Family Dept. of Chemical Engineering and Materials Science
5. Univ. of Southern California, Los Angeles, CA (United States). Dept. of Chemistry
6. Univ. of Southern California, Los Angeles, CA (United States). Ming Hsieh Dept. of Electrical Engineering. Dept. of Chemistry. Dept. of Physics and Astronomy

We report in-plane thermoelectric measurements of Bi₂Te₃ nanoplates, a typical topological insulator with Dirac-like metallic surface states, grown by chemical vapor deposition. The as-grown flakes exposed to ambient conditions exhibit relatively small thermopowers around -34 μV/K due to unintentional surface doping (e.g., gas adsorption and surface oxidation). After removal of the unintentional surface doping and surface passivation by deposition of 30 nm of Al₂O₃ using atomic layer deposition (ALD), the Seebeck coefficient of these flakes increases by a factor of 5× to -169 μV/K. We believe that the ALD-based surface passivation can prevent the degradation of the thermoelectric properties caused by gas adsorption and surface oxidation processes, thus, reducing the unintentional doping in the Bi₂Te₃ and increasing the Seebeck coefficient. The high surface-to-volume ratio of these thin (~10 nm thick) nanoplates make them especially sensitive to surface doping, which is a common problem among nanomaterials in general. An increase in the sample resistance is also observed after the ALD process, which is consistent with the decrease in doping.

• Research Organization: Univ. of Southern California, Los Angeles, CA (United States); Univ. of Texas, Austin, TX (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF) (United States)
• Grant/Contract Number: FG02-07ER46376; FG02-07ER46377
• OSTI ID: 1510945
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 8 Vol. 113; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English