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

Bong Ho Kim,Hyun Ho Gu,Young Joon Yoon

doi:10.1038/s41598-017-04222-6

Bong Ho Kim, Hyun Ho Gu + Show 1 more

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https://doi.org/10.1038/s41598-017-04222-6

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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.

Highlights

Two-dimensional (2D) transition metal dichalcogenides (TMDCs), which show a semiconducting band structure unlike graphene with a zero bandgap[1], have recently attracted a high level of interest because of their remarkable electronic and optical performance[2, 3]
We suggest a simple method of sputtering and post-processing with electron beam irradiation (EBI) to obtain crystalline MoS2 films at a low temperature below 100 °C
As the EBI process time was increased from 1 min to 10 min, the peak intensities of the E12g and A1g bands decreased without peak shifts

Summary

Introduction

Two-dimensional (2D) transition metal dichalcogenides (TMDCs), which show a semiconducting band structure unlike graphene with a zero bandgap[1], have recently attracted a high level of interest because of their remarkable electronic and optical performance[2, 3]. Several researchers have reported a direct sputtering process with a MoS2 target at a relatively low substrate temperature of 300–350 °C, but as-deposited MoS2 films show poor crystallinity compared to other methods[20,21,22]. Our EBI process makes it possible to stimulate the atomic rearrangement of amorphous MoS2 film under the conditions of a relatively low electron energy of 1 kV and short time of 1 min. We think that this EBI technique can be applied to scale up the synthetic process of MoS2 films considering its compatibility with conventional PVD processes such as sputtering and evaporation

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Conclusion