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Threshold voltage modulation in monolayer MoS2 field-effect transistors via selective gallium ion beam irradiation

通过镓离子束辐照调控单层MoS2晶体管的阈值电压

Abstract

Electronic regulation of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is a crucial step towards next-generation optoelectronics and electronics. Here, we demonstrate controllable and selective-area defect engineering in 2D molybdenum disulfide (MoS2) using a focused ion beam with a low-energy gallium ion (Ga+) source. We find that the surface defects of MoS2 can be tuned by the precise control of ion energy and dose. Furthermore, the field-effect transistors based on the monolayer MoS2 show a significant threshold voltage modulation over 70 V after Ga+ irradiation. First-principles calculations reveal that the Ga impurities in the monolayer MoS2 introduce a defect state near the Fermi level, leading to a shallow acceptor level of 0.25 eV above the valence band maximum. This defect engineering strategy enables direct writing of complex pattern at the atomic length scale in a controlled and facile manner, tailoring the electronic properties of 2D TMDCs for novel devices.

摘要

对原子层厚度二维(2D)过渡金属硫化物(TMDCs)电子属性的调 控是实现其新型光电和电子器件应用的关键. 本文采用聚焦低能量镓 离子束辐照超薄二硫化钼, 通过缺陷工程实现了原子层级的位点缺陷 调控. 研究发现二硫化钼表面缺陷可以通过精确控制镓离子束的能量 和剂量来实现低损伤的镓掺杂. 此外, 在镓离子注入后, 单层二硫化钼 晶体管的阈值电压实现了超过70 V的迁移. 第一性原理计算证实镓杂 质离子在单层二硫化钼的费米能级附近引入一个位于价带顶0.25 eV的 浅缺陷能级. 这种可控和便捷的缺陷工程方法实现了原子层深度的复 杂图样区域性掺杂, 进而调控超薄二维半导体的电学性能, 为实现高性 能的新一代光电和电子器件奠定了基础.

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Acknowledgements

This work was supported by Fujian Minjiang Distinguished Scholar Program. We acknowledge the foundation from the Department of Science and Technology of Fujian Province (2020J01704 and 2019L3008), the Scientific Research Foundation from Jimei University (ZP2020066 and ZP2020065). We thank Hiok Shian Low and Debbie Seng Hwee Leng for their technical support.

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Correspondence to Weifeng Yang.

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Author contributions

Tang B and Yang W conceived the concept and designed the experiments. Tang B and Leong JF performed the device fabrication, optimizations and characterizations. Tang B, Zhao Y and Yang W together analyzed the data, wrote and revised the manuscript. Zhou C and Zhu H designed and performed the DFT calculations. Zhang M and Shuai H contributed to the SIMS and FIB analyses. All authors were involved in the data analysis and discussion. All authors have given approval to the final version of the manuscript.

Conflict of interest

The authors declare that they have no conflict of interest.

Baoshan Tang received his PhD degree in materials science and engineering from the National University of Singapore (NUS) in 2019. Since 2019, he has been a research fellow at the Department of Electrical and Computer Engineering, NUS, Singapore. His current research focuses on the 2D semiconductors and devices, as well as the development of new technologies for next-generation neuromorphic computing.

Yunshan Zhao received his PhD degree from NUS in 2017. He worked as a research fellow at NUS until 2020. He then joined Nanjing Normal University as a full professor. His current research focuses on nanoscale energy transfer in nanostructured materials, such as phonon thermal transport in low-dimensional materials and phonon & electron engineering for thermal energy (TE) applications as well as electronics of 2D materials.

Weifeng Yang obtained his BSc degree and PhD degree in physics from Xiamen University. He then became a research fellow at Nanyang Technological University and NUS. He joined the Institute of Materials Research and Engineering, A*STAR Singapore as a scientist since 2013. He is currently a distinguished professor at Xiamen University. His research interests lie in wide-bandgap 2D semiconductors and devices in power electronic and optoelectronic applications.

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Tang, B., Zhao, Y., Zhou, C. et al. Threshold voltage modulation in monolayer MoS2 field-effect transistors via selective gallium ion beam irradiation. Sci. China Mater. (2021). https://doi.org/10.1007/s40843-021-1782-y

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Keywords

  • two-dimensional transition metal dichalcogenides
  • field-effect transistors
  • defect engineering
  • Ga ion irradiation