Ion implantation of low energy Si into graphene: insight from computational studies

By employing both molecular dynamics (MD) simulations and ab initio calculations based on the density functional theory (DFT), we studied the efficiency of doping graphene with low energy Si ions implantation. Mainly two types of substitutional doping configurations resulting from Si ion implantation were found in graphene, namely perfect Si substitution at monovacancy (Si@MV), and Si interstitial defect at divacancy site (Si@DV). High efficiency for Si substitutions was obtained within a wide energy range varied between 30-150 eV. At the optimum energy of 70 eV, up to 59% of the incident Si ions would be incorporated in graphene by Si@MV. Moreover, the experimental doping efficiency should be higher than the above value of 59% because Si adatom on graphene surface can be eventually turned into a substitution atom via annihilating with a vacancy defect produced in the collision process. Such high doping efficiency makes ion implantation a powerful tool to dope graphene with Si and similar elements. Our results provide a theoretical clue for the property engineering of graphene by using ion irradiation technique, in particular for doping graphene with heavy ions.