Fig. 4: Optical properties and interfacial charge transfer dynamics of HfN/Hf₂ON₂ heterostructure.

a UV-Vis-NIR absorption spectra of HfN/Hf₂ON₂ heterostructures with different HfN: Hf₂ON₂ ratios (1:4.5 (light red line), 1:2.1 (dark red line), 1:1.25 (pale purple line)), alongside pure-phase Hf₂ON₂ (orange) and HfN (black). b Steady-state PL spectra showing quenched emission in heterostructures. c Time resolved PL lifetime curves of HfN/Hf₂ON₂ heterostructure and the pure-phase Hf₂ON₂. d A two-dimensional pseudo-color plot of HfN/Hf₂ON₂ heterostructure with pump wavelength of 650 nm. e TA kinetics probed at different wavelengths (420 nm, 460 nm and 480 nm). f TA kinetics probed at 720 nm. g Schematic illustration of plasmon-induced hot-electron transfer in HfN/Hf₂ON₂ heterostructure after femtosecond laser pumping. h Transient current-time curves of HfN/Hf₂ON₂ photoanode at 0.27 V (vs Ag/AgCl) under monochromatic light irradiation. Source data for the Fig. 4a–h are provided as a Source Data file.