LAUSR

Abstract A two-step solvothermal synthesis was developed to fabricate BaZnO2 films on indium tin oxide (ITO)/glass and Si substrates in a mild chemical environment (pH ≅ 8) by varying the precursor concentrations, reaction times, pH values, complex agents, and type of substrates. The desirable sample was determined using the precursors of BaCl2⋅2H2O and ZnCl2 (molar ratio, 0.5:0.13) and a complex agent, polyethylene glycol (PEG). The fabrication of BaZnO2 was confirmed through X-ray diffraction and X-ray photoelectron spectroscopy. The probable formation mechanism of BaZnO2 films in this mild condition was the excellent coordination of O atoms in PEG with favored Ba2+ and Zn2+ ions. The band gap of BaZnO2 films was approximately 2.6 eV. The associated piezoelectric property was ascertained through the characterization of stress-induced piezopotentials (approximately 2 and 3 mV at approximately 1.9 and 2.9 GPa, respectively). The piezophotocatalytic application was studied by decomposing methylene blue solutions under alternating external stresses and visible light irradiation. The capability and photostability of BaZnO2 films were verified using the cycling measurement of photogenerated current (approximately 1.1 μA/cm2) in a photoelectrochemical (PEC) reaction. Another property, the incident photon-to-current efficiency, was estimated to be approximately 2.8% at a wavelength of 400 nm. Our results indicate the potential for use of BaZnO2 films in piezophotocatalysis and PEC water splitting applications.