(196l) Interface Engineering of Metal Oxynitride Heterostructures for Optoelectronic and Catalytic Applications

Photocatalysis is being studied for several decades and still enjoys significant attention in the scientific research community. It presents a great opportunity for harvesting the abundant solar energy for water splitting and CO₂ reduction reactions.^1,2 In recent times, there has been significant efforts to reduce the atmospheric CO₂, a prominent cause for global warming. Majority of the materials being investigated for solar photocatalytic applications suffers from either poor rates or stability issues. Even titania (TiO₂), one of the best catalysts till date is active only under UV light, making it unsuitable for harvesting solar energy. The metal oxynitrides can be a potential solution for this solar photoreduction of CO₂. We have studied the heterostructures of zinc oxide, aluminum nitride and gallium nitride to investigate their band gap tunability. Strain and vacancy defects are two well know phenomena that dominate material properties. We hereby probed the effect of composition, strain and different vacancy concentrations towards band gap modulation via density functional theory (DFT). Consistent trend of band gap variation was obtained with material composition variation. The effect of biaxial and vertical strain on the different heterostructures are investigated. The role of interface atoms as opposed to bulk atoms towards catalytic applications is studied via atom projected density of states (DOS). Site specificity of the anion vacancies is probed as well. These materials are thus perfect platforms for material property engineering. Strain and vacancy tuned materials are known to exhibit desired light-emitting properties. These heterostructures of metal oxy-nitrides are thus perfect for tuning electronic band states that can facilitate better charge transport, exhibit desired band edge potentials and present an opportunity to harvest visible light. This work demonstrates the versatility of these materials through systematic study on the composition, strain and vacancy effects and paves the way for future smart materials fabrication.