Sizeable bandgap modulation in Y2Hf2O7 pyrochlore oxide thin films through B-site substitution

The high-quality (111)-oriented pyrochlore oxide thin films Y2(Hf1-xIrx)2O7 (YHIO) were prepared by pulsed laser deposition. The bandgap values of Ir-substituted YHIO thin films for x = 0–0.5 range from 4.6 to 1.9 eV. Taking account of spin orbital coupling and correlation effect (U), the first-principles calculations based on density functional theory were used to intercept this variation. The theoretical results illustrate that the variation is attributed to the lower Ir 5d orbital in energy and stronger orbital hybridization between the oxygen 2p orbital and the Ir 5d orbital near the Fermi surface. These results suggest that we can widely modulate the bandgap through B-site chemical substitution based on the Y2Hf2O7 thin film.