Low-temperature epitaxial growth of high-quality GaON films on ZnO nanowires for superior photoelectrochemical water splitting. (December 2019)

• Record Type: Journal Article
• Authors: Ma, Hong-Ping; Yang, Jia-He; Tao, Jia-Jia; Yuan, Kai-Ping; Cheng, Pei-Hong; Huang, Wei; Wang, Jia-Cheng; Guo, Qi-Xin; Lu, Hong-Liang; Zhang, David Wei
• Is Part Of: Nano energy. Volume 66(2019)
• Publication Date: 2019-12
• Subjects: Gallium oxynitride -- Plasma-enhanced atomic layer deposition -- Thickness-dependent photoelectrochemical performance -- Epitaxial growth -- Electric field intensity; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2019.104089
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Gallium oxynitride (GaON) is an emerging material suitable as a key component to build efficient heterostructures for photoelectrochemical (PEC) water splitting. However, the great difficulty in controlled growth of GaON films limits their applications. This study developed a novel method for depositing highly uniform GaON films by a one-step co-deposition process via plasma-enhanced atomic layer deposition (ALD). Importantly, this material presents high-quality epitaxial growth behavior on ZnO nanowires (NWs) only at 200 °C to construct ZnO-GaON core-shell NWs with different shell thickness (5–60 nm). Benefiting from the precisely controlled ALD technique, thickness-dependent PEC performance and its mechanism were studied deeply. It was found the ZnO-GaON NWs with an optimum shell thickness (~40 nm) presented largest electric field enhancement and light-trapping ability, thus greatly improved the photocurrent from ~0.24 (pristine ZnO) to 2.25 mA/cm 2 at 1.23 V versus reversible hydrogen electrode. Meanwhile, this structure presents an ultrahigh incident photon-to-current conversion efficiency of ~90% in the UV region. A comparative study assesses the ultrahigh carrier density (~10 21 cm −3 ) and suitable bandgap of GaON relative to GaN and Ga2 O3, revealing a higher photocurrent for the ZnO-GaON core-shell NWs. These encouraging results indicated that higher PEC performance is worthy expected upon optimization of the nitrogen and oxygen concentrations and by combining with narrow bandgap materials in further studies. Graphical abstract: Image 1 Highlights: Thickness-controlled GaON film with a uniform oxygen and nitrogen composition via one-step PEALD. First report about the epitaxial growth behavior of a GaON layer on ZnO nanowires at 200 °C. A 40 nm GaON shell dramatically enhances the photocurrent of ZnO nanowires from 0.24 to 2.25 mA/cm 2 . Thickness-dependent PEC performance of ZnO-GaON is found studied well.