Defect-induced room temperature ferromagnetism in Cu-doped In₂S₃ QDs

The practical application of existing diluted magnetic semiconductors (DMSs) depends crucially on improving their room temperature ferromagnetism. Doping, as an effective method, can be used to modulate the physical properties of semiconducting materials. Herein, we report on the observation of significant RTFM in a III-VI semiconductor compound doped with nonmagnetic impurities, Cu-doped In2S3 quantum dots (QDs) grown by a gas-liquid phase chemical deposition method. The effect of Cu doping on the electronic structure and optical and magnetic properties of In2S3 is studied systematically. The UV-vis and photoluminescence (PL) spectra reveal that Cu-doped In2S3 can moderately benefit the optical properties of pristine In2S3. Magnetic measurements show that the pristine In2S3 and Cu-doped In2S3 QDs exhibit obvious RTFM, which is ascribed to the role of intrinsic defects in accordance with the bound-magnetic-polaron (BMP) theory. Furthermore, first-principles calculations based on the spin density functional theory indicate that In vacancies and their complexes with Cu dopants play a crucial role in inducing ferromagnetism. These results suggest that the Cu-doped In2S3 QDs are promising candidates for spintronics and magneto-optical applications.