(416d) Engineering Alloyed 2D Transition Metal Dichalcogenide Nanosheets Via Solution Processable Methods

The alloying of 2D TMDs is an established route to robust semiconductors with continuously-tunable optoelectronic properties. However, a major obstacle in commercializing large-area, thin devices based on alloyed TMD nanosheets is their large-scale production¹.

In this presentation we highlight our recent works addressing this issue. We begin by describing a novel powder-based, solution processable method to produce high quality 2D TMD nanosheets using a pre-annealing step and electrochemical intercalation/exfoliation². Compared to traditional methods (i.e., ultrasonication), 2D TMD nanosheets produced using this method show improved optoelectronic properties thanks to high aspect ratios and low defect densities.

Next, we demonstrate how this highly adaptable method can be used to transform commercially available, pure-phase bulk TMD powders into ternary and quaternary alloyed TMD nanosheets³. We showcase versatility by employing this technique for two classes of alloys, Mo_xW_1-xS_ySe_2-y and SnS_ySe_2-y. We provide evidence of the atomic mixing within the nanosheets using atomic resolution scanning transmission electron microscopy (STEM) in combination with integrated differential phase contrast (iDPC) for the metal and chalcogen atoms, respectively⁴. Furthermore, we show that control over the final composition of the nanosheets can be exerted by tuning the feed ratios of the TMD powders. Accordingly, we examine the unique electronic and optoelectronic properties that arise as a function of the chemical composition of the alloy. Notably, the phenomena observed are consistent with nanosheets produced via chemical vapor deposition (CVD) and related methods, suggesting that this versatile method is an economically viable solution for making alloyed 2D TMD nanosheets. Indeed, the ability to produce composition controlled TMD nanosheets in large quantities is critical for the inexpensive production of next-generation, large-area optoelectronic devices.

References:

(1) Yu, X.; Sivula, K. Toward Large-Area Solar Energy Conversion with Semiconducting 2D Transition Metal Dichalcogenides. ACS Energy Lett. 2016, 1 (1), 315–322. https://doi.org/10.1021/acsenergylett.6b00114.

(2) Wells, R. A.; Zhang, M.; Chen, T.-H.; Boureau, V.; Caretti, M.; Liu, Y.; Yum, J.-H.; Johnson, H.; Kinge, S.; Radenovic, A.; Sivula, K. High Performance Semiconducting Nanosheets via a Scalable Powder-Based Electrochemical Exfoliation Technique. ACS Nano 2022, 16 (4), 5719–5730. https://doi.org/10.1021/acsnano.1c10739.

(3) A. Wells, R.; J. Diercks, N.; Boureau, V.; Wang, Z.; Zhao, Y.; Nussbaum, S.; Esteve, M.; Caretti, M.; Johnson, H.; Kis, A.; Sivula, K. Composition-Tunable Transition Metal Dichalcogenide Nanosheets via a Scalable, Solution-Processable Method. Nanoscale Horizons 2024. https://doi.org/10.1039/D3NH00477E.

(4) Lazić, I.; Bosch, E. G. T.; Lazar, S. Phase Contrast STEM for Thin Samples: Integrated Differential Phase Contrast. Ultramicroscopy 2016, 160, 265–280. https://doi.org/10.1016/j.ultramic.2015.10.011.