Tuning the electronic structure, bandgap energy and photoluminescence properties of hexagonal boron nitridenanosheetsvia a controllable Ce3+ ions doping

Abstract

The modification of electronic structure, bandgap energy and photoluminescence properties of hexagonal boron nitride (h-BN) nanosheets has been challenging due to the inherent inertness and chemical stability of h-BN. In the present work, we realized tuning the electronic structure and bandgap energy properties of h-BN nanosheets via a controllable Ce³⁺ ions doping through a one-step facile thermal chemical reaction route using HBO₃, C₃H₆N₆ and Ce(Ac)₃·nH₂O as reactant precursors. As the Ce³⁺ ions incorporating content is lower than the critical threshold saturation value of 1.25%, the Ce-doped BN samples show an obvious band gap monotonically narrowing trend from 4.42 eV of pure BN to 3.31 eV for 1.25% Ce-doped BN nanosheets. With incorporation of Ce³⁺ ions into the lattice of h-BN, the intensity of electron paramagnetic resonance (EPR) signals closely associated with the nitrogen vacancies in Ce-doped BN samples, displays a decline trend with increasing the concentration of the incorporated Ce³⁺ ions, suggesting a decrease in the concentration of paramagnetic centers. The introduction of Ce³⁺ ions can result in the formation of a doping energy level between the conduction and valence bands of BN, and thus shifts the absorption band to the large-wavelength region, corresponding to the bandgap energy narrowing of Ce-doped BN, resulting in a red shift of the absorption edge of the Ce-doped BN samples. The B–N–O–Ce bonding due to the Ce³⁺ ion doping is responsible for bandgap energy narrowing in the Ce-doped BN materials. As the concentration of the incorporated Ce³⁺ ions reaches the critical threshold value of 1.25%, no more nitrogen vacancies are available, so the bandgap energy narrowing effect from the Ce³⁺ ion doping is reduced.