Local Modulation of Electrical Transport in 2D Layered Materials Induced by Electron Beam Irradiation

Abstract

Effective doping techniques that precisely and locally control the conductivity and carrier polarity, i.e., electron (n-type) or hole (p-type), play a vital role in the remarkable success of Si-based technology and thus are critical for developing useful devices based on two-dimensional layered transition-metal dichalcogenides (TMDs). In contrast to the previous approaches based on either chemical doping or phase transition that requires complex chemicals or a high thermal budget and shows limited tunability and reliability, we propose a simple yet effective electron-beam irradiation (EBI) technique as an alternative for facilitating polarity transformation and transport modulation in selected regions. The EBI process may generate a precise amount of native chalcogen defects in both MoS2 and MoTe2 by controlling the EBI dosage. First-principles simulations support that the presence of native chalcogen vacancies may substantially reduce the band gaps of TMDs. In MoTe2, the progressive evolution of p-type conduction, n-type conduction, to metallic-like conduction can be observed with increasing EBI dosage. The high conductivity of metallic-like MoTe2 induced by EBI is comparable to that in a metallic 1T′-MoTe2, demonstrating the ability to selectively form extremely conductive regions in semiconducting TMDs. The proposed EBI technique could be potentially applied to a wide range of layered TMDs and facilitate the development of high-performance TMD-based devices in the future.

Electronic Structure of In3–xSe4 Electron Transport Layer for Chalcogenide/p-Si Heterojunction Solar Cells

“…Moreover, it has also been reported that the band gap as well as the conductivity of the chalcogenides can be modulated using electron beam irradiation, which may also play an important role in the formation of favorable chalcogenide/p-Si heterojunction for the photovoltaic (PV) applications. 58 2.7.1. Thickness-and Doping Concentration-Dependent PV Performance.…”

Defect-engineered room temperature negative differential resistance in monolayer MoS2 transistors

“…This result can be attributed to the defect states induced by the S-vacancies, which may shift the Fermi level toward the conduction band edge, resulting in metallic-like behavior. 35,36 Accordingly, Fig. 3d–f display the corresponding I d – V g characteristics, respectively, where the NDR effect can be seen clearly in Fig.…”

p-/n-Type modulation of 2D transition metal dichalcogenides for electronic and optoelectronic devices

“…Some defects with relatively shallow energy levels would lead to the change of carrier distribution and eventually regulate conduction properties [63][64][65]. Thus, TMDCs could be intrinsically doped by the controllable intrinsic defect engineering, which has the advantages of easy patterning without any implanting impurity [66][67][68]. When synthesizing TMDCs, the defect tailoring and doping effect level could be in-situ modulated by stoichiometric ratio [67,69].…”

“…The high Se/Pt ratio was realized by a slow cool down process with a continuous supply of Se precursor, while the low Se/Pt ratio was achieved by a rapid cool down process followed by Se precursor removal. Besides the in-situ growth presented above, the defects could be also created by post-growth approaches, that all have the advantage of patterned doping capability, for instance, chemical treatment [66], plasma or electron beam etching [68,70,71], and light illumination [72]. A great example of chemical treatment for the intrinsic defect tailoring of MoS2 is presented in Fig.…”