Linear polarized photoluminescence from crystalline nanoflakes of NiPS₃ antiferromagnet prepared by wet-chemical synthesis

Using photoluminescence (PL) spectroscopy, we observe crystalline nanoflakes of NiPS₃ prepared by wet-chemical synthesis with a lateral size of about tens of nm and a thickness ranging from few to tens of nm having sharp emission peaks (< 0.1nm linewidth) with the emission wavelengths distributed from 560nm to 680nm (~2.2eV to 1.8eV) and exhibiting blinking, spectral diffusion and photobleaching characteristics. Interestingly, they show strong linear polarized emission (95% to 100%) which are dependent on the excitation linear polarization. In comparison, the exfoliated layers of 2D vdW NiPS₃ have a sharp emission peak at 842nm (1.472eV) which also shows a linear polarized emission (70% to 80%) with no dependence to the excitation polarization. We also observe multiple equidistant phonon replicas in our nanoflakes similar to the reported phonon bound states in 2D vdW NiPS₃. Considering the antiferromagnetic nature of NiPS₃ and the linear polarized emission, we attribute the sharp emission peaks to the spin-induced process analogous to the 2D vdW NiPS₃.