Tuning optoelectronic properties of 4H-SiC QDs using -H, -OH and -F surface functionalisation

Density functional calculations were performed for the -H, -OH and -F functional groups adsorbed onto the surface of pseudo-spherical 4H-SiC quantum dots with diameters ranging from 10 to 22Å. We find that for the investigated diameter range, the H-terminated SiC-quantum dots exhibit strong size dependent quantum confinement effects, while for -F and -OH terminations, the optical gap remains largely unchanged. The -H termination shows an optical absorption onset well above that of -F and -OH for a similar cluster size, which is attributed to the localisation of HOMO and LUMO states to the quantum dot core. Based on our calculations, we suggest that the -H functionalisation is a more promising route for engineering the optical properties of SiC-quantum dots, since this could lead to a wider control over the optical absorption onsets, when compared to -OH and -F terminations.