Strongly enhanced infrared absorption of HfSe2 monolayer by lanthanide doping: A first-principles study

Two-dimensional HfSe2 monolayer has great application potentials for photocatalysis and semiconductor de-vices. Using density functional theory calculations, we investigated the influence of lanthanide (LN) doping on the electronic, magnetic and optical properties of HfSe2 monolayer in this work. Compared to pristine HfSe2, which is non-magnetic with an indirect band gap, the LN-doped HfSe2 monolayers exhibit significantly altered ground states due to the introduction of defect states. Five of the considered dopants (La, Nd, Eu, Tm, and Lu) can lead to the formation of metallic ground states while the monolayer remained as semiconductor when doped with Ce and Pr. Spin polarized calculations indicate that the ground state of the Nd, Eu, Tm, and Pr doped monolayers has nonzero magnetic moment which was attributed to the unpaired f-electrons. More importantly, calculation results show that the absorption abilities of the LN doped HfSe2 monolayers with the metallic ground states are strongly enhanced in the infrared region, which suggested potential applications of such systems in solar energy harvesting. These results not only demonstrated the possibility of modulating the electronic, magnetic and optical properties of the HfSe2 monolayers via LN doping but also indicated the application po-tential of such systems for spintronics, nanoelectronics, and optoelectronics.