Zirconium Oxynitride Thin Films for Photoelectrochemical Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Thin Film Deposition

Background:

• Transition metal oxynitrides are functional materials for photoelectrochemical (PEC) applications.
• Conventional synthesis methods like ammonolysis have limitations in controlling anion ratios and substrate compatibility.

Purpose of the Study:

• To report direct reactive sputter deposition of zirconium oxynitride thin films.
• To comprehensively characterize their tunable structural, optical, and PEC properties.
• To explore their potential as photoanodes for the oxygen evolution reaction.

Main Methods:

• Direct reactive sputter deposition of zirconium oxynitride thin films.
• Systematic variation of oxygen content in the sputter gas.
• Characterization of structural, optical, and PEC properties.
• Chopped linear sweep voltammetry to assess PEC activity.
• High-vacuum annealing to study performance enhancement.

Main Results:

• Tunable crystalline structures and properties achieved by controlling oxygen content.
• Transition from metallic to semiconducting to insulating phases observed with increasing oxygen.
• Crystalline Zr₂ON₂-like films exhibit UV-visible band gaps, n-type semiconducting behavior, and favorable band edge positions for water oxidation.
• Zr₂ON₂ films demonstrated PEC activity for oxygen evolution in alkaline electrolytes.
• High-vacuum annealing improved PEC performance.

Conclusions:

• Direct reactive sputter deposition offers a versatile route to zirconium oxynitride thin films with tunable properties.
• Zr₂ON₂-like films are promising candidates for photoanode applications in PEC water splitting.
• These thin films provide a valuable platform for further research in oxynitride photoelectrodes, nanostructuring, and band gap engineering.