Ambient-Stable Inorganic Remote Modulation Doping in Two-Dimensional Transition Metal Dichalcogenide by Oxygen Plasma Treatment

Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS₂), are highly promising for next-generation electronic and optoelectronic applications. Surface charge transfer doping (SCTD) is an effective and non-destructive method to modulate the electrical properties of 2D TMDs. However, SCTD often introduces charged impurities, which can significantly hinder charge transport [1]. Previously, we addressed this limitation by demonstrating remote charge transfer doping, achieved by inserting a thin hexagonal boron nitride (hBN) layer (< 3 nm) between the MoS₂ channel and n-type molecular dopants, benzyl viologen (BV) [2]. We observed a significantly greater enhancement in the mobility of remotely doped device compared to the directly doped device at 10 K, attributed to the suppression of charged impurity scattering by the thin hBN interlayer separating BV and the MoS₂ FET channel. However, molecular doping suffers from poor long-term stability. In this study, we demonstrate an ambient-stable inorganic remote modulation doping strategy for 2D TMDs using oxygen plasma treatment. We fabricate van der Waals heterostructures in which MoS₂ is encapsulated within ~20 nm thick top and bottom hBN layers to minimize structural damage from the oxygen plasma and mitigate external substrate-induced disorders. Using this strategy, we achieve modulation of the electron density in MoS₂ through defect states induced on the top hBN surface by oxygen plasma treatment. These remotely modulated heterostructure devices exhibit carrier density controllability as well as enhanced ambient stability compared to molecularly remote-doped devices. Our work introduces a straightforward method for achieving ambient-stable remote modulation doping in 2D van der Waals heterostructures.

References
[1] J.-K. Kim et al., Adv. Mater. 33, 21015982 (2021).
[2] J. Jang et al., Sci. Adv. 8, eabn3181 (2022).