Optical Properties of MoSe₂ Monolayer Implanted with Ultra-Low-Energy Cr Ions

This paper exploresthe optical properties of an exfoliatedMoSe(2) monolayer implanted with Cr+ ions, acceleratedto 25 eV. Photoluminescence of the implanted MoSe2 revealsan emission line from Cr-related defects that is present only underweak electron doping. Unlike band-to-band transition, the Cr-introducedemission is characterized by nonzero activation energy, long lifetimes,and weak response to the magnetic field. To rationalize the experimentalresults and get insights into the atomic structure of the defects,we modeled the Cr-ion irradiation process using ab initio moleculardynamics simulations followed by the electronic structure calculationsof the system with defects. The experimental and theoretical resultssuggest that the recombination of electrons on the acceptors, whichcould be introduced by the Cr implantation-induced defects, with thevalence band holes is the most likely origin of the low-energy emission.Our results demonstrate the potential of low-energy ion implantationas a tool to tailor the properties of two-dimensional (2D) materialsby doping.