Engineering Charge Separation in α-Ga₂O₃ Nanorod Arrays for Photoelectrochemical UV Detection

Abstract

Oxygen vacancy (O V ) states are the most prevalent chemical defects in metal oxides without extrinsic dopants, which govern the regime of photoelectrochemical (PEC) kinetics. So far, although tremendous strategies are developed to overcome the negative effects from O V , the threshold at which O V plays a positive role has not been specifically studied. Furthermore, the kinetics of stoichiometry changes as well as their effects on the charge transport aroused from manipulating O V distribution are still in confusion. Here, taking α-Ga 2 O 3 nanorod arrays as the model, we show the evolution mechanism about the changes in O V distribution during vacancy engineering. Since the O diffusion flow into bulk is regulated by the surface O V -assisted migration mechanism, the surface O V concentration decreased first and recovered slightly after a period of time. This is deviated from the common sense that the longtime O 2 annealing should bring about monotonical O V decrease at the surface. After PEC characterization and theory calculation, the results show that O V plays to the score in the PEC process, depending on its own spatial distribution. The optimized engineering strategy of O V spatial distribution is proposed to establish the efficient carrier separation nanoarchitectures for high-performance UV photodetection. This work provides an insight for clarifying fundamental rules for defect engineering in the PEC field.