Presentation Information
[14p-K301-10]Impact of Nb doping on the carrier transport of monolayer MoS2
〇Mian Wei1,2, Tomonori Nishimura1, Kaito Kanahashi1, Satoru Morito3, Keiji Ueno3, Kosuke Nagashio1 (1.UTokyo, 2.Henan Univ., 3.Saitama Univ.)
Keywords:
Monolayer MoS2,Nb doping,Carrier transport
Controlling substitutional doping remains a fundamental challenge for the advancement of future 2D electronics. In bulk MoS2, Nb doping enables degenerate p-type conduction. However, achieving p-type doping in monolayer MoS2 remains inherently difficult, as its Ei increases to several hundred meV compared to the bulk, driven by quantum confinement effects and a reduced environmental dielectric constant. Consequently, a high dopant concentration is required to achieve p-type conduction. Although such high doping levels are expected to introduce significant scattering issues, a comprehensive investigation of this phenomenon remains lacking.
In this study, we conduct a systematic exploration of the impact of Nb doping in monolayer MoS2 synthesized via chemical vapor transport. It should be noted that nominal Nb concentration is used in this study.
Low-temperature PL spectra reveal that Nb doping promotes the formation of Vs, thereby implying that substitutional doping is a more complex process than initially presumed. Transfer characteristics reveal that bulk transistors exhibit degenerate p-type conduction, except for pristine bulk MoS2, while monolayer transistors maintain n-type behavior even at 3% Nb doping, attributed to the large Ei in monolayers. At doping level up to 1%, mobility shows phonon-limited transport behavior. However, at 3%, the mobility behavior transitions to thermally activated transport at lower temperatures. The mobility of MoS2 substantially degrades before sufficient doping levels for p-type behavior can be achieved, although it remains unclear whether Nb doping or Vs serves as the dominant scattering center. For the realization of high-performance p-type operation with substitutional Nb doping, the healing of sulfur vacancies is imperative.
In this study, we conduct a systematic exploration of the impact of Nb doping in monolayer MoS2 synthesized via chemical vapor transport. It should be noted that nominal Nb concentration is used in this study.
Low-temperature PL spectra reveal that Nb doping promotes the formation of Vs, thereby implying that substitutional doping is a more complex process than initially presumed. Transfer characteristics reveal that bulk transistors exhibit degenerate p-type conduction, except for pristine bulk MoS2, while monolayer transistors maintain n-type behavior even at 3% Nb doping, attributed to the large Ei in monolayers. At doping level up to 1%, mobility shows phonon-limited transport behavior. However, at 3%, the mobility behavior transitions to thermally activated transport at lower temperatures. The mobility of MoS2 substantially degrades before sufficient doping levels for p-type behavior can be achieved, although it remains unclear whether Nb doping or Vs serves as the dominant scattering center. For the realization of high-performance p-type operation with substitutional Nb doping, the healing of sulfur vacancies is imperative.
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