Ab-initio investigation of Er3+ defects in tungsten disulfide

Abstract

We use density functional theory (DFT) to explore the physical properties of an $E{r}_W$ point defect in monolayer $W{S}_2$. Our calculations indicate that electrons localize at the dangling bonds associated with a tungsten vacancy ($V_W$) and at the $E{r}^{3+}$ ion site, even in the presence of a net negative charge in the supercell. The system features a set of intra-gap defect states, some of which are reminiscent of those present in isolated $E{r}^{3+}$ ions. In both instances, the level of hybridization is low, i.e., orbitals show either strong Er or W character. Through the calculation of the absorption spectrum as a function of wavelength, we identify a broad set of transitions, including one possibly consistent with the $E{r}^{3+}$ $4I_{15/2}\to 4I_{13/2}$ observed in other hosts. Combined with the low native concentration of spin-active nuclei as well as the two-dimensional nature of the host, these properties reveal $Er:W{S}_2$ as a potential platform for realizing spin qubits that can be subsequently integrated with other nanoscale optoelectronic devices.