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Optoelectronic Synapse Behaviors of HfS2 Grown via Molten Salt Flux Method

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Abstract

Layered two-dimensional materials are promising candidates for next-generation semiconductor platforms owing to their atomically thin bodies, and it is crucial to develop a method for their large-scale synthesis for integrating these materials into the fabrication process. Here, we report the synthesis of a centimeter-scale HfS2 ingot using the molten salt flux method (MSFM). The structure, crystallinity, and uniformity of the synthesized HfS2 sample were verified using X-ray diffraction and Raman spectroscopy. The chemical properties were investigated using X-ray photoelectron spectroscopy. A HfS2 synaptic field effect transistor (FET) was fabricated to confirm its electrical uniformity and semiconducting nature, with an average mobility of 10.6 cm2 V-1 s-1. The synaptic plasticity of the HfS2 synaptic FET was investigated by applying light pulses (405 nm) in different modulation configurations. Paired-pulse facilitation was achieved by applying a continuous light pulse with a negative gate bias voltage. The modulation of synaptic weight was demonstrated under different stimulation conditions, which emulates the human brain. Furthermore, the linearity of the HfS2 synaptic device was optimized based on the frequency of the pulses to enhance learning accuracy. The approach reported here encourages the large-scaled production of transition metal dichalcogenides (TMDs) for use in artificial synaptic transistors.

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The data supporting the plots and other findings are available from the corresponding author upon request.

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Acknowledgements

This study was supported by the National Research Foundation of Korea (NRF) grants funded by the Government of the Republic of Korea (2021R1C1C1012209 and RS-2023-00275300) and by the Korea Institute of Ceramic Engineering and Technology (KPP22002). This results was also supported by “Regional Innovation Strategy (RIS)” through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE) (2021RIS-003). Following are results of a study on the “Leaders in INdustry-university Cooperation 3.0” Project, supported by the Ministry of Education and National Research Foundation of Korea.

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  1. Mi Ji Kwon and Nguyen Vu Binh contributed equally to this work.

Authors and Affiliations

  1. Department of Materials Engineering and Convergence Technology, Gyeongsang National University, Jinju, 52828, South Korea

    Mi Ji Kwon & Jun Hong Park

  2. School of Materials Science and Engineering, Gyeongsang National University, Jinju, 52828, South Korea

    Su-yeon Cho, Soo Bin Shim & Jun Hong Park

  3. Electronic Convergence Materials Center, Korea Institute of Ceramic Engineering & Technology, Jinju, 52851, South Korea

    Nguyen Vu Binh, So Hyun Ryu, Yong Jae Jung, Woo Hyun Nam & Jung Young Cho

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  1. Mi Ji Kwon
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Contributions

M. J. K. and N. V. B. prepared the materials for most of the experimental measurements and analyzed the results. M. J. K., J.Y.C., and J. H. P. conceived and designed the study. S. C., S. B. S., S. H. R., and Y. J. J. assisted with material characterization and W. H. N conducted the XPS analysis. M. J. K. fabricated the devices and analyzed the results. M. J. K., N. V. B., J. Y. C., and J. H. P. wrote the manuscript. All the authors discussed the results and commented on the manuscript. All authors revised the manuscript. J. H. P. supervised the study.

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Correspondence to Jung Young Cho or Jun Hong Park.

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Kwon, M.J., Binh, N.V., Cho, Sy. et al. Optoelectronic Synapse Behaviors of HfS2 Grown via Molten Salt Flux Method. Electron. Mater. Lett. (2024). https://doi.org/10.1007/s13391-024-00494-z

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