LaFeO3thin films were successfully epitaxially grown on single-crystalline SrTiO3substrates by the one-step hydrothermal method at a temperature of 320 °C in a 10 mol/L KOH aqueous solution using La(NO3)3and Fe(NO3)3as the raw materials. The growth of the films was consistent with the island growth mode. Scanning electronic microscopy, elemental mapping, and atomic force microscopy demonstrate that the LaFeO3thin films cover the SrTiO3substrate thoroughly. The film subjected to hydrothermal treatment for 4 h exhibits a relatively smooth surface, with an average surface roughness of 10.1 nm. X-ray diffraction in conventional Bragg–Brentano mode shows that the LaFeO3thin films show the same out-of-plane orientation as that of the substrate (i.e., (001)LaFeO3||(001)SrTiO3). The in-plane orientation of the films was analyzed by φ-scanning, revealing that the orientational relationship is [001]LaFeO3||[001]SrTiO3. The ω-rocking curve indicates that the prepared LaFeO3films are of high quality with no significant mosaic defects.
High-performance formaldehyde sensors act a significant role in environmental monitoring and industrial gas analysis. However, the traditional side-heating type gas sensors fabricated by handicraft-like brush-painting or drop-casting methods still suffer from poor detection limits and the difficulty of massive fabrication, which hinders the further practical applications of gas-sensing devices. Herein, the uniform LaFeO 3 thin film prepared through a facile sol-gel method combining with spin coating is proposed to achieve batch-fabricated gas sensors for the detection of gaseous formaldehyde. The fabricated gas sensor exhibits a low detection limit as low as 50 ppb toward gaseous formaldehyde, which is lower than the guideline value (80 ppb) limited by World Health Organization. Furthermore, the gas-sensing properties of batch-fabricated thin film gas sensors reveal satisfactory uniformity and replicability with low device-to-device deviation. The maximum variation of baseline resistance between different batch samples is only 5.4%, and the maximum drift of the response value toward formaldehyde is only 6.5%. The favorable gas-sensing performances and high replicability for the sensors might be attributed to the controllable fabrication process that can be completely compatible with the well-established semiconductor technics. This work will open up an effective pathway to prompt high-performance formaldehyde sensors with ppb-level detection limits toward practical applications.
危险品化学品经营许可证（带存储）