Establishing Constellations and Quantification of individual Ion-Implanted Dopants in Monolayer MoS₂  

Session

Poster Session One

Authors

Dr Michael Hennessey (2), Dr Eoghan O'Connell (2), Dr Manuel Auge (1), Dr Eoin Moynihan (2), Prof Hans Hofsaess (1), Prof Ursel Bangert (2)

Affiliations

1. University of Goettingen
2. University of Limerick

Keywords

Two-dimensional (2D) materials, high resolution scanning transmission electron microscopy (STEM), low energy ion implantation for doping of  2D materials, image modelling

Abstract text

Atomic resolution imaging of two-dimensional (2D) materials using scanning transmission electron microscopy (STEM) has become a commonly employed method to locate individual foreign atoms in 2D materials and to identify their nature and constellation via their contrast in high angle annular dark-field (HAADF) STEM. In order to understand the effect of these impurity atoms on the host material, there is need to locate and quantify them on a larger scale. Here STEM images of MoS2 monolayers, doped via ultra-low energy ion-implantation with Chromium, have been analyzed, using functions from the open-source TEMUL Toolkit, whereby an atomic model of an experimental image, based on the positions and intensities of the atomic columns in the image, is created and refined. The refined model is then used to determine the elemental composition on each atomic site. Using this method significant atom statistics can be achieved and utilized to calculate the retention rate of the implanted ions within the host lattice. The results show that the implanted chromium ions have been successfully integrated into the transition metal sublattice, replacing ~ 4.1% of molybdenum atoms. It has furthermore been demonstrated that positions of individual dopants , e.g., of Selenium implants in MoS2, and their effect on the re-arrangement of atoms in the chalcogen sublattice can be determined on the sub-atomic scale.