Atomic rearrangement of a sputtered MoS2 film from amorphous to a 2D layered structure by electron beam irradiation

Abstract

We synthesised a crystalline MoS2 film from as-sputtered amorphous film by applying an electron beam irradiation (EBI) process. A collimated electron beam (60 mm dia.) with an energy of 1 kV was irradiated for only 1 min to achieve crystallisation without an additional heating process. After the EBI process, we observed a two-dimensional layered structure of MoS2 about 4 nm thick and with a hexagonal atomic arrangement on the surface. A stoichiometric MoS2 film was confirmed to grow well on SiO2/Si substrates and include partial oxidation of Mo. In our experimental configuration, EBI on an atomically thin MoS2 layer stimulated the transformation from a thermodynamically unstable amorphous structure to a stable crystalline nature with a nanometer grain size. We employed a Monte Carlo simulation to calculate the penetration depth of electrons into the MoS2 film and investigated the atomic rearrangement of the amorphous MoS2 structure.

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS2 Films

“… 13 In contrast, crystallization of a-MoS 2 , as followed here at the atomic scale, has previously been studied only at comparatively large fields of view, insufficient to discern details on the single atom level, be it in or ex situ from thermal activation 11 , 37 − 40 , 51 , 52 or e-beam irradiation. 39 , 52 − 54 In contrast to previous work, our high-resolution STEM data now allow us to discuss atomic-scale details of the crystallization and restructuring processes based on direct in situ information.…”

Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers

“…The Moirè fringes, resulting fr of the nanocrystals with the unde exhibit in this case a pattern with than the one observed in the TEM It can be useful to recall that th iodicity depends on the difference parameters of the two crystals form similar the two parameters, the lar Kim et al [82] deposited five to seven atomic layers of MoS 2 on a SiO 2 /Si wafer at room temperature using the RF magnetron sputtering method. The thickness of the deposed amorphous MoS 2 layers was about 4 nm.…”

“…To understand the irradiation-induced defects well, the synthesis/preparation details of the as-prepared MoS 2 layers will be described in each section in addition to irradiation. [75] mono-layer electron 60 keV 10 6 -10 9 electron /nm 2 STEM beam 400-700 • C in vacuum induced 2H/1T phase transition [76] ∼10 layer electron 3-15 keV n/a EPMA in vacuum broke the inversion symmetry [77] mono-layer electron 80 keV n/a TEM beam in vacuum removed top and bottom S atoms [78] mono-layer electron 200 keV 3000 electrons/nm 2 /s TEM beam in vacuum created S vacancies, increased electric resistance [79] mono-layer electron 15 keV 280 µC/cm 2 EBL in vacuum produced local strain and changed band structure [80] mono-layer electron 80 keV 40 A/cm 2 TEM beam in vacuum produced holes and Mo 5 S 3 nanoribbons [81] amorphous 5-7 layer electron 1 keV 1-10 min EBI in vacuum crystallized [82] mono-layer U 238 1.14 GeV 4000 ions/cm 2 heavy ion accelerator in vacuum total damaged [83] micron thickness Ar + 500 eV 2.26 × 10 15 ions/cm 2 plasma UHV produced S vacancies [84] bi-layer Ar + 500 eV 10 14 -10 15 ions/cm 2 plasma UHV produced S vacancies and MoS 6 vacancy clusters [84] mono-layer Ar + 500 eV 2.26 × 10 15 ions/cm 2 plasma UHV damaged [84] 200 µm thickness proton 3.5 MeV 5 × 10 18 ions/cm 2 Singletron facility RT preserved lattice structure, produced defects, changed magnetic moments [85] few-layer proton 10 MeV 10 12 -10 14 ions/cm 2 MC-50 cyclotron n/a decreased electrical conductance [86] mono-layer proton 100 keV 10 12 -10 15 particles/cm 2 LEAF n/a created defects [87] bi-layer proton 100 keV 6 × 10 14 particles/cm 2 LEAF n/a created defects [87] bulk He 2+ 1.66 MeV 900 MGy ion accelerator n/a changed Raman scattering slightly [88] nanosheet He 2+ 1.66 MeV 900 MGy ion accelerator n/a invariant [88] few-layer He 2+ 30 keV 10 18 ions/cm 2 FIB beam in vacuum milled or damaged [89] mono-layer He 2+ 3.04 MeV 8 × 10 13 particles/cm 2 PTA n/a produced defects [90] mono-layer He + 30 keV 10 12 -10 16 ions/cm 2 HIM in vacuum produced S vacancies [91] mono-layer He + 30 keV 10 13 -10 17 ions/cm 2 NFM in vacuum ...…”

Molybdenum Sulfide Prepared by Atomic Layer Deposition: Synthesis and Characterization

“…This suggestion does not explain the lack of a Raman signal, but if the crystal is highly disordered then the vibrational modes may be weak and broad. The lack of a Raman signal has been seen previously in sputtered MoS2, but after an electron beam irradiation step, the fundamental Raman peaks appeared [75].…”