講演情報
[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.)
キーワード：
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.