NO2 sensing characteristics by α-Fe2O3 nanorod arrays with atomic layer deposited amorphous Al2O3 overlayer

We have grown α-Fe2O3 nanorods by solution processing followed by the deposition of Al2O3 overlayer using atomic layer deposition. Al2O3 layer was deposited for two different thicknesses 4 nm and 8 nm and a post-deposition annealing at 550 °C for 2 h in air atmosphere was performed. Crystallinity an...

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Bibliographic Details
Published in:Nano express 2024-06, Vol.5 (2), p.025030
Main Authors: Dhua, Swati, Singh, Ashish K, Rani, Sanju, Rath, Jatin K, Roy, Somnath C
Format: Article
Language:English
Subjects:
Aluminum oxide
amorphous Al
amorphous Al2O3
atomic layer deposition
Atomic layer epitaxy
Charge transport
Crystallization
Electrons
Fe
gas sensing
Gas sensors
High resolution electron microscopy
Image resolution
nanorod
Nanorods
Nitrogen dioxide
NO2
Operating temperature
Photoelectrons
Room temperature
Sensitivity
Temperature
Temperature dependence
X ray photoelectron spectroscopy
α-Fe2O3
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Summary:We have grown α-Fe2O3 nanorods by solution processing followed by the deposition of Al2O3 overlayer using atomic layer deposition. Al2O3 layer was deposited for two different thicknesses 4 nm and 8 nm and a post-deposition annealing at 550 °C for 2 h in air atmosphere was performed. Crystallinity analysis through x-ray diffraction (XRD) reveals that the α-Fe2O3 nanorods crystallized into rhombohedral structure, whereas the outer Al2O3 layers remained largely amorphous. Interestingly, the interface showed signs of AlFexOy formation as observed through high-resolution transmission electron microscopy images. Gas sensing characteristics were studied using NO2 with 10, 50, and 100 ppm concentrations at operating temperatures of 30 °C, 100 °C, 150 °C and 190 °C. The room temperature sensitivity values obtained in response to 10 ppm NO2 were 31%, which surpassed the previously reported values. A higher concentration of surface adsorbed oxygen on the Al2O3 overlayer, as revealed by the x-ray photoelectron spectroscopy (XPS) analysis, led to enhanced NO2 sensing at room temperature. A lower activation energy (0.29 eV) of barrier to charge transport for Al2O3 coated α-Fe2O3 nanorods compared to that of bare nanorods (0.45 eV), as calculated from the temperature dependent I-V measurements, supported observation of higher sensitivity at room temperature.
ISSN:2632-959X
DOI:10.1088/2632-959X/ad585b