Dr. Danny Fox
Photonics and Nanofabrication Group
CRANN Advanced Microscopy Laboratory
Trinity College Dublin, Ireland
A method to controllably introduce defects and modify the structure of layers of molybdenum disulphide (MoS2) at the nanoscale is described. A helium ion microscope was used to introduce defects while Raman spectroscopy and Energy dispersive X-ray spectroscopy (EDX) were used to analyse the resulting change in crystal structure and stoichiometry. By using an appropriate He+ dose, the defect density as well as the stoichiometry of MoS2 can be tuned at a few-nm scale. Fabrication of nanostructures of MoS2 with sub 10 nm dimensions was also achieved. The sub-nm probe size of the He+ beam facilitated the fabrication of MoS2 nanoribbons with pristine crystal structure down to 7 nm wide. Nanoribbons with widths as small as 1 nm were reproducibly fabricated, however their structure was found to be amorphous. This nanoscale modification technique can also be applied to the range of other two-dimensional materials which are currently under intense research investigation.