Few-layered MoS₂ has electronic properties that can be tuned with the material thickness and crystal structure, making it attractive for a multitude of applications including next-generation optical and electronic devices. Doping MoS₂ crystals through substitution or adsorption of transition metals has been shown to improve carrier concentration and mobility values while lowering the contact resistance. [1-3] Prior work has investigated the altered physicochemical properties caused by additions of metal atoms into the MoS₂ lattice, but there is a significant lack of understanding and control of how dopants affect the crystallization and growth processes of the materials during synthesis. For manufacturing of highly-controlled MoS₂ and related materials, improved knowledge of how to control the material structure during the growth process itself is essential. In this study, we combine in situ transmission electron microscopy (TEM) with ex situ investigation to determine how the addition of transition metal dopants influences the crystallization and growth of MoS₂ materials from a solid-state amorphous precursor. Low concentrations of Ni are observed to cause significant differences in the MoS₂ crystallization and growth process, leading to an increase in resulting MoS₂ crystal size. This is likely a result of the observed altered mobility of interfaces between crystals in the presence of Ni, which is known to substitute at edge sites, during heating-induced growth. Addition of other metallic dopants, such as Cu, Fe and Co, did not result in similar increases in MoS₂ crystallite size. Ongoing experiments building on the insights from this study aim to understand the influence of these metal atoms on the electronic and optical properties of few-layer MoS₂ films. These findings demonstrate the important role of additional elements in controlling the evolution of TMDCs during synthesis, which should be considered when designing these materials for a variety of applications.

References

[1] Zhao, Y., Xu, K., Pan, F., Zhou, C., Zhou, F., & Chai, Y. Doping, Contact and Interface Engineering of Two-Dimensional Layered Transition Metal Dichalcogenides Transistors. Advanced Functional Materials, 2017, 27.

[2] Gao, J., Kim, Y. D., Liang, L., Idrobo, J. C., Chow, P., Tan, J., et. al. Transition-Metal Substitution Doping in Synthetic Atomically Thin Semiconductors. Advanced Materials, 2016, 28, 9735–9743.

[3] Lockhart De La Rosa, C. J., Arutchelvan, G., Leonhardt, A., Huyghebaert, C., Radu, I., Heyns, M., & De Gendt, S. (2018). Relation between Film Thickness and Surface Doping of MoS₂ Based Field Effect Transistors. APL Materials, 2018, 6, 58301.