Nb Doping and Alloying of 2D WS2 by Atomic Layer Deposition for 2D Transition Metal Dichalcogenide Transistors and HER Electrocatalysts

Jeff J P M Schulpen; Cindy H X Lam; Rebecca A Dawley; Ruixue Li; Lun Jin; Tao Ma; Wilhelmus M M Kessels; Steven J Koester; Ageeth A Bol

doi:10.1021/acsanm.4c00094

Nb Doping and Alloying of 2D WS₂ by Atomic Layer Deposition for 2D Transition Metal Dichalcogenide Transistors and HER Electrocatalysts

ACS Appl Nano Mater. 2024 Apr 1;7(7):7395-7407. doi: 10.1021/acsanm.4c00094. eCollection 2024 Apr 12.

Authors

Jeff J P M Schulpen¹, Cindy H X Lam¹, Rebecca A Dawley², Ruixue Li³, Lun Jin³, Tao Ma⁴, Wilhelmus M M Kessels¹, Steven J Koester³, Ageeth A Bol^{1

2}

Affiliations

¹ Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands.
² Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States.
³ Department of Electrical and Computer Engineering, University of Minnesota, 200 Union Street Se, Minneapolis, Minnesota 55455, United States.
⁴ Michigan Center for Materials Characterization, University of Michigan, 2800 Plymouth Road, Ann Arbor, Michigan 48109, United States.

Abstract

We utilize plasma-enhanced atomic layer deposition to synthesize two-dimensional Nb-doped WS₂ and Nb_xW_1-xS_y alloys to expand the range of properties and improve the performance of 2D transition metal dichalcogenides for electronics and catalysis. Using a supercycle deposition process, films are prepared with compositions spanning the range from WS₂ to NbS₃. While the W-rich films form crystalline disulfides, the Nb-rich films form amorphous trisulfides. Through tuning the composition of the films, the electrical resistivity is reduced by 4 orders of magnitude compared to pure ALD-grown WS₂. To produce Nb-doped WS₂ films, we developed a separate ABC-type supercycle process in which a W precursor pulse precedes the Nb precursor pulse, thereby reducing the minimum Nb content of the film by a factor of 3 while maintaining a uniform distribution of the Nb dopant. Initial results are presented on the electrical and electrocatalytic performances of the films. Promisingly, the Nb_xW_1-xS_y films of 10 nm thickness and composition x ≈ 0.08 are p-type semiconductors and have a low contact resistivity of (8 ± 1) × 10² Ω cm to Pd/Au contacts, demonstrating their potential use in contact engineering of 2D TMD transistors.