• Hart, Judy Nancy
• He, Jiaqing
• Valanoor, Nagarajan
• Webster, Richard Francis
• Park, Collin Keon Young
• Gharavi, Paria Sadat Musavi
• Xie, Lin

Abstract

The origins of recently reported visible-light photoelectrochemical activity in ZnS–GaP (ZG) multilayer films are investigated using aberration-corrected scanning transmission electron microscopy (STEM). It is revealed that the multilayers carry a large volume fraction of defects, specifically stacking faults and twins, at the interfaces. The defects act as excellent channels for diffusion. For each ZG interface, a ∼5 nm-interdiffused region with an effective chemical composition of a ZnS–GaP solid solution is observed. Previous theoretical calculations have found that ZnS–GaP solid solutions possess a lower band gap than either GaP or ZnS and thus are expected to have better visible-light photo-activity. These findings are thus able to explain the observed commensurate increase in the visible-light photoelectrochemical response with increasing number of ZG layers. This work suggests that interfaces with intentionally designed lattice imperfections and/or intentionally driven interdiffusion leading to local solid solution formation provide a new materials design strategy for achieving efficient visible-light photo-activity.

Topics

• impedance spectroscopy
• chemical composition
• transmission electron microscopy
• defect
• stacking fault
• interdiffusion