Optimal electron irradiation as a tool for functionalization of MoS2: Theoretical and experimental investigation

Abstract

We demonstrate the utility of electron irradiation as a tool to enhance device functionality of graphene-analogous MoS2. With the help of first-principles based calculations, vacancy-induced changes of various electronic properties are shown to be a combined result of crystal-field modification and spin-orbital coupling. A comparative theoretical study of various possible vacancy configurations both in bulk and monolayer MoS2 and related changes in their respective band-structures help us to explain plausible irradiation induced effects. Experimentally, various structural forms of MoS2 in bulk, few layered flakes, and nanocrystals are observed to exhibit important modification of their magnetic, transport, and vibrational properties, following low doses of electron irradiation. While irradiated single crystals and nanocrystals show an enhanced magnetization, transport properties of few-layered devices show a significant increase in their conductivity, which can be very useful for fabrication of electronic devices. Our theoretical calculations reveal that this increase in n-type conductivity and magnetization can be correlated with the presence of sulfur and molybdenum vacancies.

Electron beam-formed ferromagnetic defects on MoS2 surface along 1 T phase transition

“…Additionally, similar to graphene6, developing approaches to effectively induce the ferromagnetism into the diamagnetic 2H-MoS 2 have attracted a great interest for possible spintronics and quantum information devices, but it is still challenging78910111213141516171819202122. Extensive experimental and theoretical studies have effectively modified magnetic properties of MoS 2 with the various forms of thin films7, nanoribbons8, nanosheets9, and even in bulk limit1011.…”

“…Extensive experimental and theoretical studies have effectively modified magnetic properties of MoS 2 with the various forms of thin films7, nanoribbons8, nanosheets9, and even in bulk limit1011. The used methods are by the formation of vacancies111213, adsorbing non-metal atoms1415 substitutional doping TM atoms1617 and application of an external electric field1819 or elastic strain2021, and so on. Notably, together with high-Curie-temperature, relatively large ferromagnetism has been only realized in the significant presence of zigzag edges722.…”

“…Accordingly, for a magnetic MoS 2 , 1 T phase incorporation has been also explored by using the chemical exfoliation303132. As a separate method, irradiation with low-energy electrons has been also used to modify the magnetic and transport properties13. However, although the achieved magnetic moments are remarkable1332, it is still obscure whether the magnetism originates intrinsically from the existence of 1 T phase or edge effect driven by the various defects2033.…”

“…As a separate method, irradiation with low-energy electrons has been also used to modify the magnetic and transport properties13. However, although the achieved magnetic moments are remarkable1332, it is still obscure whether the magnetism originates intrinsically from the existence of 1 T phase or edge effect driven by the various defects2033. Thus, with a full understanding of 1 T phase incorporation, it is desirable to find more effective ways to control and improve the magnetic and electrical properties of MoS 2 .…”

Investigation of electron irradiation-induced magnetism in layered MoS2 single crystals

“…More recently, electron irradiation with low energy (below 30 keV) has been used to improve both magnetic and electrical properties of MoS 2 . 18 The approach using electron beam-based techniques enables the electronic structure to be engineered via tailoring the atomic structures. [19][20][21][22] Particularly, monosulfur vacancies (V S 's) are frequently observed in transmission electron microscope (TEM) measurements, 23 where the electron beam (80 keV) is lower than the displacement energy of S atoms (90 keV) [Mo atoms (560 keV)].…”